summary measures of population health,report of findings of methodologic and data issues

8/8/2019 Summary measures of population health,Report of findings of methodologic and data issues

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Contents

1. SummaryMeasuresofPopulationHealth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Overview of the Role of Summary Measures in Health. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

1.2.1 The process of population health change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2.2 Past use of summary measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.3PotentialSummaryMeasuresSuggestedforHealthyPeople2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51.4 Availability of Data for Estimating the Proposed Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2. MethodsforCalculatingHealthyLifeExpectancy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.2 The Life Table Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.2.1 Estimating the average expectation of life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.2.2 Estimating healthy life expectancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2.3 Standard errors of healthy life expectancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113. ExpectedYearsofHealthyLifeUnderVariousDefinitionsofHealth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.2 Expected Years of Healthy Life for Males and Females. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2.1 Expected years in good or better health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.2.2 Expected years without activity limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.2.3 Expected years without work limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.2.4 Expected years without functional dependency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.2.5 Expected years without diseases or chronic conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.2.6Expectedyearswithbodymass index(BMI) less than25andyearswithBMI lessthan30 . . . . . . . . . 18

3.3 Expected Years of Healthy Life for the White and Black Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203.3.1Expectedyearsingoodorbetterhealthfor thewhiteandblackpopulations . . . . . . . . . . . . . . . . . . . . . . 203.3.2Expectedyearswithoutanyactivitylimitationforthewhiteandblackpopulations. . . . . . . . . . . . . . . . . 213.3.3ExpectedyearswithoutADLorIADLlimitationforthewhiteandblackpopulations. . . . . . . . . . . . . . . 223.3.4 Expected years with BMI less than 30 for the white and black populations . . . . . . . . . . . . . . . . . . . . . . 22

3.4 Comparison of Results from the Various Measures of Health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243.4.1 Comparison across measures at 30 and 65 years of age . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253.4.2 Comparison across measures for males and females at 65 years of age. . . . . . . . . . . . . . . . . . . . . . . . . . . 253.4.3Comparisonacrossmeasuresforthewhiteandblackpopulationsat65yearsofage . . . . . . . . . . . . . . . 273.4.4 Comparison across measures by age, sex, and race . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

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4. TrendsinLifeFreeofActivityLimitation:UnitedStates,198595. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 424.2Age-AdjustedDeathandActivityLimitationRates:UnitedStates,198595. . . . . . . . . . . . . . . . . . . . . . . . . . . 424.3Age-SpecificDeathandActivityLimitationRates:UnitedStates,1985and1995 . . . . . . . . . . . . . . . . . . . . . . 434.4 Years Free of Activity Limitation: United States, 198595 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444.5GainsinLifeExpectancyandExpectedLimitation-FreeYears:UnitedStates,198595. . . . . . . . . . . . . . . . . . 454.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

5. TheImpactofIncompleteDataonHealthyLifeExpectancyEstimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 525.2The1995NoninstitutionalizedCivilianandInstitutionalizedPopulations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

5.2.1 The noninstitutionalized civilian population. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545.2.2 The 1995 nursing home population. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

5.3 Functional Limitation: The Community and Nursing Home Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545.3.1 Functional limitation: The population 5 years of age and over. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 555.3.2 Functional limitation: The population 65 years of age and over . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

5.4 Effect on Healthy Life Expectancy Estimates for the Older Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586. SummaryandConclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Figures1.1 Population health change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Potential health changes for individuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 Health care and public health intervention opportunities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.1 A schematic presentation of the model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2 Aschematicframeworkforestimatinghealthylifeexpectancyat thenationallevelusingrespondent

assessed health status as an example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.3 Example of attributes for health classification system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.1 Percentageofpersonsreportinggoodorbetterhealth,byageandsex:UnitedStates,1995 . . . . . . . . . . . . . . . 143.2 Percentageofexpected lifeingoodorbetterhealthatbirth,20,and65yearsofage,bysex:

United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143.3 Percentage free of activity limitation, by age and sex: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.4 Percentageof lifeexpectancyfreeofanyactivity limitationatbirth,20,and65yearsofage,bysex:

United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.5 Percentageabletoperformpersonalcareneedsornot limited inotherroutineneeds,byageandsex:

United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.6 Percentageof lifeexpectancyable toperformpersonalcareneedsornotlimitedinotherroutineneeds at 45, 65, and 75 years of age, by sex: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.7 Percentageof lifeexpectancyfreeofchronicarthritisat30,65,and75yearsofage,bysex:

United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.8 Percentageof lifeexpectancyfreeofchronicheartdiseasesat30,65,and75yearsofage,bysex:

United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

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3.9 Percentageof lifeexpectancyfreeofchronichypertensionat30,65,and75yearsofage,bysex:United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.10 Percentage not obese, by age and sex: United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193.11 Percentage in good or better health, by age and race: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213.12 Percentagefreeofanytypeofactivitylimitation,byageandrace:UnitedStates,1995 . . . . . . . . . . . . . . . . . . 223.13 Percentageabletoperformpersonalcareneedsornot limited inotherroutine

needs, by age and race: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.14 Percentage not obese, by age and race: United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233.15 Lifeexpectancyandexpectedyearsofhealthylifeunderdifferentdefinitionsofhealthat30yearsof

age, both sexes: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243.16 Lifeexpectancyandexpectedyearsofhealthylifeunderdifferentdefinitionsofhealthat65yearsof

age, both sexes: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253.17 Lifeexpectancyandexpectedyearsofhealthylifeformalesunderdifferentdefinitionsofhealthat

65 years of age: United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263.18 Lifeexpectancyandexpectedyearsofhealthylifeforfemalesunderdifferentdefinitionsofhealthat

65 years of age: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263.19 Lifeexpectancyandexpectedyearsofhealthylifefor thewhitepopulationunderdifferentdefinitionsof

health at 65 years of age: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273.20 Lifeexpectancyandexpectedyearsofhealthylifefor theblackpopulationunderdifferentdefinitionsof

health at 65 years of age: United States, 1995

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3.21 Sexdisparities inhealthundervariousdefinitionsofhealthstatus,byage:UnitedStates,1995 . . . . . . . . . . . 283.22 Racialdisparitiesinhealthbetweenwhiteandblackpopulationsundervariousdefinitionsofhealthstatus,

by age: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294.1 Number of deaths per 1,000 for white males, by age: United States, 1985 and 1995 . . . . . . . . . . . . . . . . . . . . . 434.2 Numberofdeathsper1,000forwhitefemales,byage:UnitedStates,1985and1995 . . . . . . . . . . . . . . . . . . . 434.3 Number of deaths per 1,000 for black males, by age: United States, 1985 and 1995 . . . . . . . . . . . . . . . . . . . . . 444.4 Numberofdeathsper1,000forblackfemales,byage:UnitedStates,1985and1995 . . . . . . . . . . . . . . . . . . . 444.5 Percentageofwhitemaleswithactivitylimitationfromanycause,byage:UnitedStates,1985

and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444.6 Percentageofwhitefemaleswithactivitylimitationfromanycause,byage:UnitedStates,1985

and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454.7 Percentageofblackmaleswithactivity limitationfromanycause,byage:UnitedStates,1985

and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 454.8 Percentageofblackfemaleswithactivitylimitationfromanycause,byage:UnitedStates,1985

and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464.9 Expectedyearsfreeofactivitylimitationaspercentageoflifeexpectancy,whitemales:UnitedStates,

1985 and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464.10 Expectedyearsfreeofactivitylimitationaspercentageoflifeexpectancy,whitefemales:UnitedStates,

1985 and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 464.11 Expectedyearsfreeofactivitylimitationaspercentageoflifeexpectancy,blackmales:UnitedStates,

1985 and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474.12 Expectedyearsfreeofactivitylimitationaspercentageoflifeexpectancy,blackfemales:UnitedStates,

1985 and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 475.1 Percentageof thefemalepopulation65yearsofageandoverwhoneedhelpwithat leastoneactivityof

daily living, by age and residence: United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 545.2 Percentageof thefemalepopulation65yearsofageandoverwhoneedhelpwithat leastone

instrumentalactivityofdaily living,byageandresidence:UnitedStates,1995 . . . . . . . . . . . . . . . . . . . . . . . . 555.3 Percentageof thefemalepopulation65yearsofageandoverwhoneedhelpwithat leastoneactivity

of daily living, by age and residence: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 565.4 Percentageof thefemalepopulation65yearsofageandoverwhoneedhelpwithat leastoneactivity

ofdailylivingorinstrumentalactivityofdaily living,byageandresidence:UnitedStates,1995 . . . . . . . . . . 57

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TextTablesA. Ratesperthousandwithchroniccondition,bytypeofconditionandsexatselectedages:UnitedStates,

199496. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17B. Classificationofoverweightandobesitybybodymass index(BMI):Adults,18yearsofageandover . . . . . 19C. Thecommunityandinstitutionalizedpopulation,bysex:UnitedStates,1990 . . . . . . . . . . . . . . . . . . . . . . . . . . 52D. Percentagedistributionof thenoninstitutionalizedandinstitutionalizedpopulation,bybroadagegroup:

United States, 1990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53E. Percentagedistributionandsexratioofcommunitydwellersand thenursinghomepopulation,bybroadage

group: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

DetailedTables3.1. Lifeexpectanciesandexpectedyearsingoodorbetterhealthandexcellenthealthforselectedages,

by sex: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303.2. Lifeexpectanciesandexpectedyearswithout limitationinactivityforselectedages,bysexandtypeof

activity: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313.3. Lifeexpectanciesandexpectedyearswithoutworklimitationforselectedages,bysex:

United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323.4. Lifeexpectanciesandexpectedyearswithoutfunctionaldependencyforselectedyears,bysex:

United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333.5. Lifeexpectanciesandexpectedyearswithoutchronicarthritisandchronicheartdiseasesforselectedages,

by sex: United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343.6. Lifeexpectanciesandexpectedyearswithoutchronichypertensionandchronicdiabetesforselectedages,

by sex: United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353.7. Lifeexpectanciesandexpectedyearswithbodymass index lessthan25andyearswithbodymass index

less than 30 for selected ages, by sex: United States, 199496. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363.8. Lifeexpectanciesandexpectedyearsingoodorbetterhealthforselectedagesof thewhiteandblack

populations, by sex: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373.9. Lifeexpectanciesandexpectedyearswithoutanytypeofactivitylimitationforselectedagesofthe

white and black populations, by sex: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383.10. Lifeexpectanciesandexpectedyearswithout limitationinpersonalcareorotherroutineneedsfor

selected ages of the white and black populations, by sex: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . 393.11. Lifeexpectanciesandexpectedyearswithbodymass indexlessthan30forselectedagesof thewhite

and black populations, by sex: United States, 199496 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.12. Expectedyearsatage30and65estimatedusingdifferentdefinitionsofhealth,byhealthstatus:

United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403.13. Expectedyearsatage65estimatedusingdifferentdefinitionsofhealth,byhealthstatusandsex:

United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 413.14. Expectedyearsatage65estimatedusingdifferentdefinitionsofhealth,byhealthstatusandrace:

United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 414.1. Age-adjusted death rates for all ages, by race and sex: United States, 198595 . . . . . . . . . . . . . . . . . . . . . . . . . 484.2. Age-adjustedactivity limitationratesfromanycauseforallages,byraceandsex:

United States, 198595. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 484.3. Numberofdeathsfromallcausesfor thewhiteandblackpopulations,bysex:UnitedStates,1985and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4.4. Limitationofactivityfromanycauseforthewhiteandblackpopulations,bysex:UnitedStates,1985and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

4.5. Lifeexpectancyandexpectedyearsfreeofanyactivity limitationformalesatbirth,byrace:United States, 198595. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

4.6. Lifeexpectancyandexpectedyearsfreeofanyactivity limitationforfemalesatbirth,byrace:UnitedStates,198595. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

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4.7. Lifeexpectancyandexpectedyearsfreeofany limitationatbirth,age20,andage65for thewhiteandblackpopulations, by sex: United States, 1985 and 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.1. Numberandpercentagedistributionofcommunityresidentsbysexandbyrace,according toageatinterview: United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

5.2. Numberandpercentagedistributionofnursinghomeresidentsbysexandbyrace,accordingtoageatinterview: United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

5.3. Percentageofpopulationneedinghelpwithatleastoneactivityofdailylivingandneedinghelpwithatleastoneactivityofdailylivingorinstrumentalactivityofdaily living,bybroadagegroup,sex,andplaceof residence: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

5.4. Percentageofpopulationneedinghelpwithatleastoneactivityofdailyliving,byage,sex,andplaceof residence: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

5.5. Percentageofpopulationneedinghelpwithatleastoneactivityofdailylivingorinstrumentalactivityof daily living, by age, sex, and place of residence: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

5.6. Expectedyearsof lifeandhealthyyearsoffemalecommunitydwellersandnursinghomeresidentsatselected ages: United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6.1. Absoluteandrelativedifferences inmaleandfemalehealthy lifeexpectancyat30and65yearsofage:United States, 1995. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

6.2. Absoluteandrelativedifferences inmaleandfemalehealthy lifeexpectancyfor thewhiteandblackpopulations at 30 and 65 years of age: United States, 1995 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

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1. SummaryMeasuresofPopulationHealth1.1 Introduction

Theconceptofhealthexpectancywasintroducedinthe

1960s(1)andfurtherdevelopedin the1970s(24).Inmore

recentyears,bothpolicymakersandmembersofthe

researchcommunityhavebeenincreasinglyinterestedinthe

estimationofhealthylifeexpectancy.Thisinterestarises

fromthefactthatmeasuresofhealthylifeexpectancy

potentiallyoffereasilycomprehensiblemeasuresofboththe

levelof,andchangein,thewell-beingofapopulation.

Becausethesemeasuresincorporatebothmortalityand

morbidity,theyseemhighlyappropriateassummary

measuresofhealthintheolderpopulation,wheretherehas

beenconsiderablemortalitydecline,butwherethereis

concernthattheextensionoflifemaynotbeequivalentto

theextensionofhealthylife.Therelationshipbetweenchangesinmortalityand

morbidityandtherelativelygreaterburdenofmorbidityin

theolderagesgainedinterestin the1980s.Debatecentered

onwhetherthefactorsresponsibleforthereductionsin

mortalitywouldhaveasimilareffectonmorbidity.Some

arguedthatmostoftheyearsoflifethattheelderlygained

duetothedeclineofmortalitywerehealthyyearseither

becausetheincidenceofchronicconditionswasbeing

pushedtothelastfewyearsoflife,thatis,thecompression

ofmorbidity(5,6)orbecausethelossoffunctioningor

disabilityfromchronicconditionshadsloweddown(7).

Othersarguedthat themedicalcareimprovementsthatsaved

liveswerenotaccompaniedbyeitherdiseasepreventionthatwouldmaintainhealthystatesorhealthcarethatwould

delayfunctionalconsequencesofdisease(8).

Healthylifeexpectancyisalsoperceivedasausefultool

forhealthplanningandmakinghealth-relatedpolicy

decisions.Anindicationoftheperceivedusefulnessfor

policymakersoftheconceptofhealthylifeexpectancyis

thefactthatyearsofactivelifearenowincludedamong

nationalandinternationalhealthgoals.Fortheyear2000,

theU.S.goalwas65yearsofactivelifeexpectancyatbirth

forthetotalpopulation(9).Thetwooverarchingnational

healthgoalsidentifiedforHealthyPeople2010areto:+

Increasethequalityandyearsofhealthylifeand+ Eliminatehealthdisparities(10).

Thegoalsandobjectivesoutlinedforthedecadein

HealthyPeoplehavebecomecentraltobothmonitoringthe

Nationshealthandplanninganagendatopromotehealth

andpreventill-health.Monitoringthegoalsandobjectives

fortheyear2010will,inpart,beachievedthroughLeading

HealthIndicators,asmallnumberofmeasuresthataddress

majordeterminantsofhealth.TheseLeadingHealth

Indicatorsprovideawayofunderstandinghealthinthe

future,buttherealsohasbeenaneedtodescribe,ina

summaryway,thecurrenthealthof thepopulation.Somesummarymeasurescombineboththequalityand

quantityoflifetoreflectyearsofhealthandcanbeusedto

monitorprogresstowardthe firstof theoverarchinggoals.

Becausetheyarecomparableacrosspopulationswith

differentagestructures,thesemeasuresalsocanbeuseful

formonitoringprogresstowardthesecondgoalof

eliminatinghealthdisparities.Morespecifically,summary

measuresofpopulationhealthcombineage-specific

schedulesofhealthandmortalitytoderiveglobalmeasures

ofpopulationhealththatreflectbothmortalityand

morbidity;inthisway,expectedyearsoflifecanbedivided

intohealthyandunhealthylife.Theyhavebeenproposedas

themostcomprehensivemeasuresforevaluatingoveralltrendsanddifferencesinpopulationhealth.

Asaninitialeffortinthedevelopmentofsummary

measuresofhealth,theNationalCenterforHealthStatistics

(NCHS),CentersforDiseaseControlandPrevention,

sponsoredaworkshopentitledIdentifyingSummary

MeasuresforHealthyPeople2010onSeptember1718,1998,attheUniversityofMarylandsUniversityCollege

ConferenceCenter.Thepurposeofthisworkshopwasto

identifyasetofsummarymeasuresthatcouldbeusedto

evaluateprogresstowardtheoverallgoalsofHealthyPeople2010.

Thecentralquestionaddressedat thisworkshopwashow

tobestcharacterizetheprocessofhealthchangeanddifferentialsinasetof summarymeasuresthatcouldbe

estimatedreliablyandpotentiallyusedbyFederalandState

governmentstodeterminetrendsaswellasdifferencesin

healthbyage,gender,raceorethnicity,andgeographicarea.

Theobjectivesoftheworkshopwereto:

+ ProvideabriefoverviewoftheroleofsummarymeasuresinHealthyPeople2000/2010, includingreportingrequirementsanddataconstraints;

+ Identifyasetofpotentialsummarymeasuresthatshouldbeconsideredformonitoringprogresstowardthefirst

goalofHealthyPeople2010;+ Specifyabilitytocomputethepotentialmeasureswith

existingdatacollectionsystemsorcost-effective

modificationstoexistingdatathatwouldallowthe

computationofmeasures;and

+ Specifya researchagendaforthenextdecadetoevaluatepotentialsummarymeasures.

Thisreportpresentsthefindingsofresearchthatwas

initiatedinresponsetotheworkshoprecommendations.The

SummaryMeasuresofPopulationHealth 1


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workfocusesonmethodologicanddataissues.Thereport

providesdefinitionsofconceptsandmethodsforcalculatingthe

recommendedsummarymeasures;evaluatesanumberof

possiblemeasuresofmorbidity;reviewsthetrendsovera

decadeforonemeasureofhealthylifeexpectancy;and

examinestheeffectofcombiningdatafromdifferentsources.

1.2Overviewof theRoleofSummaryMeasures inHealth

Thischaptersummarizesconceptualmaterialabout

healthandmortalitythatisidentified,summarized,

measured,andtrackedwithsummarymeasures.Inorderto

identifytheprospectivesummarymeasuresthatbestmonitor

thequalityandyearsofhealthylife(i.e.,oneofthe

overarchinggoalsofHealthyPeople2010) it isnecessarytofirstclarifythedimensionsofpopulationhealthandshow

howtheyarerelatedtohealthbehaviorsandpotential

interventions.

Mortalityoftenhasbeenusedasabasicindicatorof

health.Lifeexpectancyisthemostfrequentlyusedsummarymeasureofmortalityconditionsbecauseitsummarizes

mortalityratesacrosstheentireagerange. Two

characteristicsoflifeexpectancymakeita valuablemeasure

forportrayingmortalityconditionstoaudiencesthatinclude

thegeneralpublicandpolicymakers.First, itisnotaffected

bypopulationage-structure.Thismeansthatvaluescanbe

comparedfordifferentsubgroupsofthepopulationatone

pointintimeorforthesamegroupsatdifferentpointsin

time.Inaddition,becauselifeexpectancyisexpressedin

yearsoflife,itiseasilyinterpretedbybothpolicymakers

andthepublic.Bothofthesecharacteristicsmakelife

expectancyanessentialtoolformonitoringbothtrendsand

differencesinmortalityforthepopulationandsubgroupsofthepopulation.Consequently,extendingthisstatistical

concepttoincorporatevariousstatesofhealthmaygenerate

acceptableandunderstandablestatistics.

Theextensionofthebasiclifetablemodeltoinclude

measuresofhealthcanbeusedtocreatesummarymeasures

ofpopulationhealththatdivideexpectedlifeintohealthy

andunhealthyyears(11,12).Whenhealthstatusisdominated

bychronicconditionsatolderagesratherthaninfectious

diseasesatyoungerages,itispossibletohavebothlonger

lifeanddeterioratingpopulationhealth(13).Forinstance,if

increasedtreatmentofheartdiseaseresultsinmortality

decline,peoplewill livelongerwiththedisease; this,in

turn,willresultinincreasedheartdiseaseprevalence,

especiallyifnewcasesarenotprevented.Iftheyearsoflife

livedwithheartdiseasecontinuetobecharacterizedby

diminishedfunctioning,overallpopulationhealthwill

deteriorateaslifeexpectancyincreases.

Theassociationbetweenmortalitychangeandhealth

changeisweakenedfurtherbecausemanycausesof

morbidityarenotfatalconditions.Forinstance,osteoarthritis

isamongtheleadingcausesofdisabilityamongolder

people,butitisnotalikelycauseofdeath.Asmortality

fromothercausesdeclines,osteoarthritisprevalencecould

increase.Summarymeasuresthatcombinemortalityand

morbidityattemptto capturetheseaspectsofhealthstatus.

1.2.1TheprocessofpopulationhealthchangeThekeyissueindevelopingsummarymeasuresis

definingandmeasuringhealthandhealthchange.Individual

researchersandinternationalgroupshavedonesignificant

workindefiningthedimensionsofhealthandclarifyingthe

processofpopulationhealthchange(14,15). Aconceptual

outlineofthedimensionsofhealthandtheprocessof

changeinpopulationhealthisshowninfigure1.1(16).Any

orallofthedimensionsofhealthcouldbecapturedin

summarymeasures.

Diseases,conditions,andimpairments(e.g.,heart

disease,arthritis,andvisualimpairment)occurbeforethere

isalossinfunctioningortheabilitytoperformcertain

actions(e.g.,walkingablock,climbinga specificnumberof

stairs,orsittingforanallottedtime).Functioninglosscan

thenresultindisabilityoran inabilitytoperforman

expectedsocialrole,oftendefinedasworkforthe

middle-agedandself-careor independentlivingforanolder

population.Deathistheendoftheprocess.Overtime,

changecanoccurinsomeorallofthesedimensions,thatis,

gettingorlivingwithdiseases,experiencingfunctioningloss,

anddying(17).

Disabilityin thiscontextreferstothesituationinwhich

anindividualsabilitiesorlimitationsaredeterminedbythe

interactionoftheirphysical,mental,orcognitivestatuswith

theenvironmentinwhichtheywouldperformsocialroles.

Thedegreeof limitationordisabilityisdependentonhow

Figure1.1.PopulationhealthchangeSOURCE:VerbruggeandJette. TheDisablementProcess.SocialSciencesandMedicine,1994.

2 SummaryMeasuresofPopulationHealth


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wellthepersonalenvironmentaccommodatesthelossin

functioning.Thisdefinitionisequivalenttothatdevelopedin

theInstituteofMedicalModel(18)andsimilartothe

participationdimensionoftheInternationalClassificationof

Functioning,DisabilityandHealth.Inothercontexts,

disabilityisusedtorefertothephysical,mental,or

cognitivestatusoftheindividual.Althoughconsiderable

workhasbeendoneoverthelastfewyearstoward

clarifyingthemeaningofdisability,thereisstillsomeconfusioninvolvingterminology.However,researchersare

comingtomoreofaconsensusthatdisabilityisacomplex

phenomenonandthatneitherofthedefinitionsoutlined

aboveadequatelydescribesallthecharacteristicsofthe

phenomenon.

Thisschemeisonlyappropriateforpopulationhealth

change,notindividuallifecyclechange.Thecomplexityof

changeattheindividuallevelisshowninfigure1.2.Each

arrowrepresentsapotentialhealthchangeforanindividual.

Thesumofthesechangesacrossallindividualsis,of

course,whatproduceschangeinthepopulation.Any

individualcanskipstagesandmaynotnecessarily

experienceanystageotherthandeath.Individualscanalsoexperiencechangeinbothdirections,thatis,theymay

becomeimpairedandmayregainfunctioning.For

populations,however,theorderofhealthchangein

figure1.1isappropriate;onaverage,diseaseoccursfirst,

followedbyfunctioninglossanddisability,andfinally,

death.Thedifferencebetweenindividualsandpopulationsis

important inevaluatingthetypeofdataandmethodsused

forsummarymeasures.Informationontheindividual

processesrequireslongitudinaldataandmethods;

informationonthepopulationmaybecollectedas

cross-sectionalinformation.

1.2.2PastuseofsummarymeasuresSummarymeasuresofpopulationhealthcanbe

categorizedintotwomajorgroups.Thefirstmajorgroupof

measuresiscalledhealthexpectancy(HE),andincludes

measuressuchasdisability-freelifeexpectancy(DFLE)and

healthylifeexpectancy(HLE).Thesecondmajorgroup,

whichmeasureshealthgaps,includeshealthmeasuressuch

asdisability-adjustedlifeexpectancy(DALY)(19).Although

thesummarymeasuresthatindicateyearsofhealthyand

non-healthylifederivedfromthesetwogeneralapproaches

(andtheirmyriadvariations)maylooksimilar tothe

consumeroftheresearchfindings,summarymeasures

currentlyinusearebasedonavarietyofhealthoutcomes,

assumptions,andmethods.Thesedifferencesareimportantbecausetheyrelatetothevalidityandreliabilityofthe

measures.Becausetheoutcomesofallmeasuresappear

similarandareexpressedinyearsoflife,theymayallbe

equallyacceptabletothegeneralpublic;however,

researchersevaluatethepotentialusesoftheindicesquite

differently.Summarizinghealthismadeconsiderablymore

complexbytheneedformultiplemeasuresandtheneedto

lookathealthylifeasmeasuredinbothyearsandasa

percentageofremaininglifespentinthehealthystate.This

evidencesupportstheconclusionthattherearenosimple

measuresofhealth.

Healthylifeexpectancy(HLE)Thissummarymeasurethatlinkshealthdimensionsandmortalitywasproposedmorethan30yearsago(1,3).Themethodsdevelopedby

Sullivan,atNCHS,havebeenadoptedworldwideandare

thebasisfortheHLEfamilyofmeasures(20).(Seechapter

2fordetailsofthemethodology.) Asubstantialbodyof

workusingSullivansproposedsummarymeasuresandwith

modificationstofitavailabledatahasbeendevelopedover

thelast10years.Modificationstotheoriginalformulation

areduetothespecificdimensionofhealthusedindefining

healthylife.Oftenapplicationsofthismethodhavebeen

determinedbyavailabledatamorethananyclear theoretical

ideaofwhataspectofhealthisappropriate.Mostofthis

researchhasfocusedoncomparinglengthoflifeindifferent

healthstatesatvariouspointsintimeandacrosspopulationgroupsatonepointintime.

Theoriginallyproposedmeasurelinkedmortalityto

measuresoflong- andshort-termdisabilitytoestimatelife

withandwithoutdisabilityusingdatafromtheNational

Figure1.2.PotentialhealthchangesforindividualsSummaryMeasuresofPopulationHealth 3


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HealthInterviewSurvey(NHIS)(3). Yearslivedwith

disabilitycouldbefurtherdividedintosevereormoderate

disabilityandyearsoflifeinan institution.

Inthelast10years,anumberofadditionalapproaches

tomeasuringhealthylifeexpectancyusingdifferent

generalizationsofdisabilityorhealthhavebeendeveloped.

Forinstance,intheolderpopulation,disabilityhasoften

beenindicatedbytheinabilitytoperformActivitiesofDaily

Living(ADL)orInstrumentalActivitiesofDailyLiving(IADL),taskswhichreflectaninabilityto live

independently.Otherestimatesofhealthylifeexpectancy

havebeenbasedonmeasuresthatcategorizeyearsoflife

usingdiseasestatesor lossof cognitivefunctioningas

measuresofhealthstate.Forexample,healthylifeis

estimatedasyearswithoutheartdiseaseoryearswithout

impairedcognitivefunctioningordementia.

Measuresofhealthylifeexpectancyhavebeenusedto

trackandexplainchangesinpopulationhealth.Forexample,

researchbyCrimminsandassociateshasshownthatthe

1980swereaperiodwhenincreasesinlifeexpectancywere

concentratedinyearswithoutdisability; incontrast,gainsin

lifeexpectancyduringthe1970swereindisabledyears.Thisapproachhasalsobeenimportantindeterminingage,

socioeconomic,andracialdifferentials(21,22).Hayward

andHeron(1999)havelookedattherelationshipbetween

disabilityandlifeexpectancyforethnicgroupsinthe

UnitedStates;theirresearchhasshownthatsomeethnic

groupshavelongerlifebutworsehealth(Native

Americans)thanthenon-Hispanicwhitepopulation,while

othershavelongerlifeandbetterhealth(Asian

Americans)(23).

Thehealthylifeexpectancymeasuresdescribedabove

incorporatenominallydefinedstatesofhealth,andthey

estimatelifewithandwithouthealthinthesenominally

definedstates.Inordertoexpandtherangeofhealthincludedinthedefinitionofhealthylife,someresearchers

haveweightedstatesofhealthaccordingtoanindexof

healthproblemseverity.Measuresofhealthylifedeveloped

inthismannermayweightstatesthatcharacterizeone

dimensionofhealthorcombinehealthdimensionsintostates

whichareweightedtoproduceamultidimensionalindexof

healthylifeexpectancy.Thesemeasures,oftencalled

Health-AdjustedLifeExpectancies(HALE)or

Health-AdjustedLife Years(HALY),canuse awidevariety

ofdimensionstodefineasetofhealthstatestowhichthe

weightingschemeis thenapplied.Theseincludesocial

functioning,cognitivefunctioning,socialactivities,

psychologicalfunction,painandsymptoms,aswellasloss

infunctionanddisability.Theweightingschemesprovidea

numberrangingfrom 0 to 1 toreflectthequality oflifeor

thesocialutilityof thehealthstateindividuals

experience(24).Optimalhealthisvaluedat1;deathisvaluedat0.Thesemeasuresarethenintegratedwithlife

tablestoproducehealth-adjustedlifeexpectancy.Because

theweightsaresoimportantindeterminingtheoutcome,

andbecausetheyhavegreatsocialsignificance,mucheffort,

discussion,andevaluationhasgoneintoproducingthe

weightingschemesforuseinthesemeasures.Agreementhas

notbeenreached,however,on thevalidityofthevarious

schemes.

Insummary,measuresreflectinghealthylifeexpectancy

canbebasedonavarietyofdefinitionsofhealthandcan

utilizeavarietyofmethods.Nosinglemeasurehasbeen

agreeduponasthebestapproach.Theappropriatenessof

measuresdependsonthedimensionsofhealthofprimaryinterest(e.g.,disabilityordisease).If thereisadesireto link

thesemeasurestohealthpoliciesandprogramsandto

individualhealthbehaviors,thepointsof interventioninthe

healthprocessshouldbeconsidered (figure1.3).Observed

changesinthesemeasurescanreflectarangeof factors.

Healthylifeexpectancycanbebroughtaboutbychangesin

risk-relatedhealthbehaviors(becauseoftechnologicalor

medicaladvancementaffectingthediagnosis,treatment,and

progressionofdiseases)orbecausedisabilityhasbeen

reduced(bybetterintrinsichealthorbecausetheextrinsic

environmentbecomesmoreadaptedtopersonswith

functioningproblems).Consequently,careandadditional

dataarerequiredtointerprettheanalysesunderlyingthesestatistics.

Disability-AdjustedLifeYears(DALYs)The WorldBankand WorldHealth Organizationhavesupported a

projecttodevelopmethodstoevaluatethedistributionof

scarcehealthresourcesindevelopingcountries.Asaresult,

thereisnowagrowinginterestinanotherapproachto

summarymeasuresDisability-AdjustedLife

YearsDALYs(2532).DALYsrepresentanalternative

Figure1.3.Healthcareandpublichealth interventionopportunities4 SummaryMeasuresofPopulationHealth


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approachtosummarymeasureconstructionthatlinks

disease,disability,anddeath.Thisapproachestimatesyears

oflifelostfromdeathswhichoccurbeforesome

theoreticallyachievableage(e.g.,internationalreportsuse80

yearsformenand82.5yearsforwomen)andattributingthis

losstodeathrates.Next,yearslosttononfataldiseasesare

calculatedbylinkingtheincidenceofdiseasestodisability

levelsandlengthoftimewithdisability.DALYsdifferfrom

othermeasuresdescribedbecausetheyreflectyearslosttoill-healthinsteadofyearslivedwithill-health;another

differenceis that theylinktwomajordimensionsofhealth:

diseaseanddisability.

DALYsalsoincorporateweightstoreflecttheseverityof

disability,and,becauseoftheemphasisonhealthpolicyin

theinternationalapplications,DALYsincorporatean

additionaleconomicapproachtoweightingyearsof life.

Thisapproachgivescurrentyearsoflifehigherweightsthan

futureyearsoflife,andlifeintheproductiveyearsor

workingagesisgivenhigherweightsthanlifein

nonproductiveyears.Theseweightingschemesdramatically

affecthowyearsofhealthylifearecalculatedforpeopleof

differentagesaswellasforpeoplewithdifferentdisabilities.

Incontrasttothecross-sectionalSullivanapproachto

estimatinghealthylifeexpectancy,DALYshavebeen

developedasanincidence-basedmeasure,thatis,onethatis

basedon thetransitionintodiseaseordisability.Incidenceis

aflowmeasure,whereasprevalenceisa stockmeasure.

Researchershavelongrecognizedthatincidenceratesare

theoreticallypreferabletoprevalencedataforindicating

healthchange:incidenceratesreflectonlyrecentevents,

whileprevalencedatareflecteventsthatoccurredearlierina

personslifetime.Incidencerates,however,require

longitudinaldatafromlargesamples,andtheyusuallyare

notavailableformostconditionsorfornationallyrepresentativepopulationsofmostages.

Becausetheincidencedatarequiredforinputto the

DALYsdonotexist,theyhavebeenestimatedfrom

whateverepidemiologicalinformationcanbepieced

together.Forexample,community-basedsurveyslikethe

FraminghamStudyprovideasourceofinformationon

diseaseonset.Disabilitylevelsrelatedtodiseaseonsetwere

thendeterminedusingexpertopinions. Weightsfor the

valueof lifespentindisease-disabilitylevelswerethen

developedinaseriesofworkshopswithavarietyof

experts.

1.3PotentialSummaryMeasuresSuggestedforHealthyPeople2010

Afterdiscussingbothgeneralapproachestoestimating

summarymeasuresanda largenumberofspecific

approachestothesemeasures,workshopattendeeswere

askedtorecommendsummarymeasuresforconsideration

fortheHealthyPeople2010,keepingdataavailabilityinmind.Themostimportantrecommendationresultingfrom

thismeetingwasthat:

Nosinglemeasurecanadequatelyincorporateallaspectsof health and mortality. A set of summary measuresincludingbothmortalityandvariousaspectsofmorbidityor health that canbecalculatedfromexisting orcollect-abledatashouldbeproposedforHealthyPeople2010.Usingasetofmeasuresratherthanasinglemeasurewill

makeitpossibletotraceavarietyofhealthylifedimensions

andtonotedifferencesinvariousaspectsofhealth.Itwill

alsobepossibleto identifyprogressinsomedomainsofhealththathaveledtowhatappearstobedeteriorationin

otheraspectsofhealth.For instance,progressmadein

prolongingthelivesofpersonswithAIDS(broughtabout

byavarietyofpharmaceuticaldevelopments)may

lengthenaveragelife,increasethenumberofyearslived

withAIDS,leadtoanincreaseinthenumberofpeople

withAIDSinthepopulation,andchangethehealthstatus

ofthoselivingwithAIDS.Usingasetofsummary

measuresinsteadofasinglemeasurewillhelpclarifythe

meaningofchangeinthemostgeneralmeasuresand

disentangleeitherprogrammaticormedicalinfluences;

thus,progresstowardreachingHealthyPeople2010goalscanbebettermonitored.

Although the two types of measures,HLE andDALYs,were discussed,HLE measures were recommendedforHealthyPeople2010.Inaddition,allsuggestedmeasureswerebasedoncross-sectional data.Further investigationofthepropertiesofincidence-basedmeasuresneedstobecompletedbeforeusingthemforhealthmonitoring.Thesetofmeasuresrecommendedformonitoringthe

firstgoalofHealthyPeople2010includethefollowing:Yearsofhealthy lifedefinedaslifewithoutdisability:

Thisrepresentsoneofthemostgeneralsummarymeasures

asdisabilityisalatestageinfigure1.1andreflectspopulationhealthstatesofallthepriorhealthdimensions.

Becausedisabilityreferstotheinabilitytoperformexpected

tasks,thisdefinitionofyearsofhealthylifemayreflectthe

overallimpactofhealthproblems.Healthylifecanbe

definedaslifelivedwithoutanyhealthlimitationthat

preventsnormalactivity.Lifewithdisabilitycanbe

subdividedintolifewithsevereandmoderatedisabilityas

wellaslifewithlimitationinpersonalcare,work,or

school.Thistypeofmeasurecanclearlydefineand

characterizeahealthyyearoflife,thatis,ayearwithout

disability.

YearsofHealthyLife(asusedforHealthyPeople2000):ThesummarymeasurethatwasdevelopedforHealthyPeople2000representsmultipledimensionsofhealth(33).Itincludesbothdisabilityandtheindividualsassessmentofall

aspectsofhealth.Itshouldcontinuetobe includedamong

theHealthyPeople2010measuresforcomparisonovertimeandwithothermeasures.Thismeasureusesaweighting

scheme;thatis,itincludesseverityofhealthproblemsinthe

calculation.Itismoredifficulttodefinethemeaningofa

yearofhealthylifewiththismeasurebecauseitincorporates

multipleaspectsofhealth.



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Inadditiontothetwomeasuresabove,morenarrowly

definedmeasuresofhealthalsocanbethebasisofsummary

measuresthatarecomparableovertimeandacross

populationsubgroups.Measuresbasedonhealth-related

behaviors,functioning,disease,andself-assessedhealth,

coupledwithmortality,weresuggested.Theseadditional

measureshavethepotentialtoclarifywhichdimensionsof

healtharechangingandthuscanbelinkedtoprogramsand

policiesthatmightbecausinghealthchange.Suchmeasurescaninclude:

Yearsof lifewithoutfunctioningproblems:Summarymeasuresbasedon functioningcouldbedefinedbyabilityto

performcertainfunctions,suchaswalking,lifting,picking

upobjects,etc.For thispurpose,bothphysicalandmental

functioningshouldbeconsidered.

Yearsof lifewithoutspecifieddiseases:Summarymeasurescouldincludeyearswithoutavarietyofmajor

diseasesandconditions;theconverse,yearswithconditions,

couldalsobeestimated.

Yearsof life inexcellentorverygoodhealth:Self-perceivedhealthcanbeusedaloneina summary

measuretoreflectchangeinpeoplesassessmentof theirhealth.Lengthoflifeinexcellenthealthorinverygoodor

excellenthealthcanbeasummarymeasureascanyears

spentinpoorhealthorfairorpoorhealth.

Yearsof life livedwithgoodhealthbehavior:Thismeasurecanserveasasummarymeasureofyearsspent

withriskfactorsforsomeoftheotherhealthoutcomes.For

instance,theaverageyearswithnoriskyhealthbehavior

(e.g.,smoking,drinking,obesity,andnohealthcare)canbe

estimated.Estimatescanbebasedonsinglebehaviorsor

groupsofbehaviors. Yearswithoutanyriskbehaviorscan

alsobeestimated.

Alloftheproposedsummarymeasurescanbeconstructedwithavailabledataandshouldbeavailablefor

majorsubgroupsof thepopulation.Somecanbeconstructed

forsub-nationalgeographicalareassuchasStates.Allthe

recommendedmeasurescanbeusedtoreflectprogress

towardbothgoalsofincreasingthequalityandyearsof

healthylifeanddecreasinghealthdisparitiesastheycanbe

estimatedforgenderandmajorracialandethnicgroups.

1.4AvailabilityofDataforEstimating theProposedMeasures

Thesuggestedmeasurescanbeestimatedforanumber

ofyearsinthe1990susingavailabledatafromNHIS.

However,the1997redesignoftheNHISsurveywillmakeit

difficulttohavealengthyseriesforsomeof themeasures.

Forsubgroupsofthepopulation,itmaybenecessaryto

combineyearstoproducereliableestimatesforsomeage,

racial,andethnicgroups.Onenecessarycomponentofthe

measuresistheannuallifetableforthepopulationalong

withthelifetablesfor thesubgroupsofinterest.Lifetables

bysocioeconomicstatus(SES)arenotregularlyproduced

butcouldbeproducedusingdatasuchasthemortality

followupforNHIS.Considerationshouldbegiventothe

reliabilityofannualchangesofmortalityaswellashealth

data.

Itwillbeimportanttoapplythesemeasuresacross

variousgeographicandpoliticallevels,includingStatesand

municipalities.Manyofthesemeasurescanbeestimatedfor

States.Thepossibilityofestimatingthesestatisticsfor

smallergeographicareasneedstobeinvestigated.Estimates

fortheinstitutionalpopulationneedtobeincludedinthesummarymeasures.Estimatesofthesizeandcompositionof

therelevantinstitutionalpopulationaredifficulttoobtainbut

needtobepartofthemeasuresiftheyaretodescribethe

entirepopulation.Issuesofdataavailabilityforthe

institutionalpopulationneedtobeaddressed.

Thisreportpresentstheresultsofresearchconductedto

investigatevariousissuesofimmediateinterestfor

monitoringprogresstowardtheHealthyPeople2010goals.Healthylifeexpectancieswereestimatedusingdifferent

definitionsofhealth.Selectedestimatesforvarious

populationsubgroupsarepresentedin chapter 3.Allofthe

estimatespresentedinthechapterarecalculatedbasedon

healthdatafromNHIS.SinceNHISdoesnotincludetheinstitutionalpopulation,theestimatesin chapter 3mightbe

atvariancewithestimatesmadeincludingtheinstitutional

population.Thepossibleimpactofnotincludingthe

institutionalpopulationinestimatinghealthylife

expectanciesisdiscussedin chapter 5. Twootherimportant

pointsshouldbekeptinmindinreadingtheestimated

healthylifeexpectanciesin thisreport.First, theexpected

yearsofhealthylifepresentedinthisreportaredifferent

fromthe YearsofHealthyLife(YHL)usedinHealthyPeople2000 inboththeinterpretationoftheresultsaswellasinthemethodofcalculation.(Themethodofcalculation

andinterpretationofYHLusedinHealthyPeople2000isdescribedinStatisticalNotesno 7(33).)Second, thesurveyinstrumentsandmethodofdatacollectionofNHISwere

revisedin1997.However,sinceallNHISdatausedinthis

reportarefromsurveysconductedpriorto1997,the1997

revisionofNHISdoesnotaffecttheresultsofthisreport.

DatausedforthisreportaremainlyfromtheNCHSand

theU.S.CensusBureau.Themethodthatiswidelyusedfor

calculatinghealthylifeexpectationusingcross-sectiondata

isexplainedsuccinctlyfollowingthisintroductorychapter.

Expectedyearsofhealthylifeundervariousdefinitionsof

healthandvariationofresultsbymeasurearediscussedin

chapter 3.Chapter 4summarizestrendsinyearsfreeof

activitylimitationfortheperiod198595.Inadditionto

estimatinghealthylifeexpectancyunderdifferentattributes

ofhealthandlookingat trendsinlimitation-freelife,the

reportincludesatestoftheeffectofincludingdatafrom

differentsourcesonestimatedhealthyorlimitation-free

years.Anillustrationofthis impactanalysisispresentedin

chapter 5.Theoverallsummaryofthereportand

recommendationsforthelongertermendeavorofsolving

problemsofdataconstraintsandtheconstructionofmore

comprehensivemodelsofsummarymeasuresofhealthare

highlightedinthelastchapter.

6 SummaryMeasuresofPopulationHealth


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References1. SaundersB.Measuringcommunityhealthlevels.Am JPublic

Health54106370.1964.

2. SullivanDF.Conceptualproblems indevelopinganindexof

health. VitalandHealthStatistics,2(17):NationalCenterfor

HealthStatistics, Washington,D.C.1966.

3. SullivanDF. Asingleindexofmortalityandmorbidity.

HSMHSHealthReports86:34754.1971a.

4. SullivanDF. Disabilitycomponentsforanindexofhealth.VitalandHealthStatistics.2(42)NationalCenterforHealth

Statistics,Rockville,Maryland.1971b.

5. FriesJF. Aging,naturaldeath,andthecompressionof

morbidity. NEngl J Med303(3):1305.1980.

6. FriesJF.Thecompressionofmorbidity:Nearorfar. Milbank

Q67(2):20832.1989.

7. MantonKG.Changingconceptsofmorbidityandmortalityin

theelderlypopulation.MilbankQ:HealthSociety60(2):

183224.1982.

8. Gruenberg EM.Thefailureofsuccess.MilbankQ:Health

Society55(1):324.1997.

9. U.S.DepartmentofHealthandHumanServices,Officeof

DiseasePreventionandHealthPromotion.Healthypeople

2000. Washington,D.C.1991.10. U.S.DepartmentofHealthandHumanServices.Healthy

people2010.2nded. Withunderstandingandimproving

healthandobjectivesforimprovinghealth. 2vols.

Washington,D.C.:U.S.GovernmentPrintingOffice.2000.

11. FieldMJ, GoldMR.(eds).Summarizingpopulationhealth:

Directionforthedevelopmentandapplicationofpopulation

metrics.InstituteofMedicine,NationalAcademyPress,

Washington,D.C.1998.

12. U.S.DepartmentofHealthandHumanServices.Leading

indicatorsforhealthypeople2010: AreportfromtheHHS

workinggroupon sentinelobjectives.U.S.Government

PrintingOffice. Washington,D.C.1998.

13. CrimminsE,HaywardMD,Saito Y.Changingmortalityand

morbidityratesandthehealthstatusandlifeexpectancyoftheolderU.S.population.Demography31:15975.1994.

14. VerbruggeL.Disabilityinlatelife.InAgingandqualityof

life.AbelesR,GiftH,and Ory M.(eds).pp.7998.Springer,

New York.1994.

15. WorldHealthOrganization.Internationalclassificationof

impairment,disabilitiesandhandicaps: A manual of

classificationrelatingto theconsequencesofdisease.Geneva.

1980.

16. VerbruggeLM,JetteAM.Thedisablementprocess.SocSci

Med38(1):114.1994.

17. CrimminsE,HaywardMD,Saito Y.Differentialsinactivelife

expectancyin theolderpopulationof theUnitedStates. J

Gerontol BPsycholSciSocSci51(B3):S111S120.1996.

18. BrandtEN,PopeAM.Eds.EnablingAmerica:Assessingtheroleofrehabilitationscienceandengineering.Divisionof

HealthSciencesPolicy,InstituteofMedicine,National

AcademyPress, Washington,D.C.1997.

19. MathersE.Healthexpectancies:anoverviewandcritical

appraisal.InSummarymeasuresofpopulationhealth:

Concepts,ethics,measurementandapplications.C.J.L.

Murray,etal. (eds).pp.177204.WHO,Geneva.2002.

20. JaggerC.HealthexpectancycalculationbytheSullivan

Method: Apracticalguide.Euro-REVES.1997.

21. CrimminsE,Saito Y,IngegneriD.Changesinlifeexpectancy

anddisability-freelifeexpectancyintheUnitedStates.

PopulationandDevelopmentReview15:23567.1989.

22. CrimminsE,Saito Y,IngegneriD. Trendsindisability-free

lifeexpectancyintheUnitedStates19701990.Population

andDevelopmentReview23(3):55572.1997.

23. HaywardMD,HeronM.Racialinequalityinactivelife

amongadultAmericans.Demography36(1):7791.1999.24. FrybackD.Methodologicalissuesinmeasuringhealthstatus

andhealth-relatedqualityoflifeforpopulationhealth

measures: Abriefoverviewofthe HALYFamilyof

Measures.InSummarizingpopulationhealth:Directionsfor

thedevelopmentandapplicationofpopulationmetrics.Field

MJandGoldMR.(eds).NationalAcademyPress,

Washington,D.C.1998.

25. MurrayC,LopezA.Globalandregionalcause-of-death

patternsin 1990.Bulletinofthe WorldHealthOrganization

72(3):44780.1994a.

26. MurrayC,LopezA.Quantifyingdisability:Data,methods,

andresults.Bulletinofthe WorldHealthOrganization

72(3):48194.1994b.

27. MurrayC,LopezA.Evidence-basedhealthpolicyLessonsfromtheglobalburdenofdiseasestudy.Science274(1):

7403.1996a.

28. MurrayC,LopezA.Theglobalburdenofdiseases: A

comprehensiveassessmentofmortalityanddisabilityfrom

diseases.Injuriesandriskfactorsin1990andprojectedto

2020.Cambridge:HarvardUniversityPress.1996b.

29. MurrayC,LopezA.Alternativeprojectionsofmortalityand

disabilitybycause19902020:GlobalBurdenofDisease

Study.Lancet349(24):14981504.1997a.

30. MurrayC,LopezA.Globalmortality,disability,andthe

contributionofriskfactors:GlobalBurdenofDiseaseStudy.

Lancet349(17):143642.1997b.

31. MurrayC,LopezA.(1997c).Mortalitybycauseforeight

regionsoftheworld:GlobalBurdenofDiseaseStudy.Lancet349(3):126976.1997c.

32. MurrayC,LopezA.Regionalpatternsofdisability-freelife

expectancyanddisability-adjustedlifeexpectancy:Global

BurdenofDiseaseStudy.Lancet349(10):134752.1997d.

33. EricksonPW, WilsonR,ShannonI. Yearsofhealthylife.

StatisticalNotes,no7.Hyattsville,Maryland:NationalCenter

forHealthStatistics.1995.



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2. MethodsforCalculatingHealthyLifeExpectancy2.1 Introduction

Healthylifeexpectanciesarecalculatedusingmodelsthatincorporatemeasuresofmortalityandmorbidityas

schematicallypresentedin figure2.1(1).

Age-specificdeathratesaccountforthemortality

component.Age-specificratesofpopulationmorbidity,

disability,or someotheraspectofhealthaccountforthe

morbiditycomponent.Thesetwocomponentsarecombined

usinga mathematicalfunctionthattransformsthetwosetsof

partialmeasuresintoasinglecompositemeasureusinga life

tablemethodology.Figure2.2displaystheframeworkofthis

calculation,includingthetypeofdataneededandthe

techniquesusedtoestimatethetwocomponentsofthe

measureatthenationallevel.

NationalmortalitydataareobtainedfromtheNationalVitalStatisticsSystemofNCHS.Mortalitydataarecollected

byeachStateandtheDistrictofColumbiaandcompiledat

thenationallevelbyNCHS.Mid-yearpopulationestimates

arefromtheU.S.CensusBureau.

Healthdatacancomefromanumberofdifferent

sources,dependingonthetypeofhealthmeasureandthe

populationbeingconsidered.Therangeofitemsthatcould

beusedtocharacterizehealthisillustratedbyahealthstate

classificationsystemdeveloped byBoyleand Torrance

(displayed,inpart,infigure2.3) (2).Theclassification

systemofBoyleand Torranceconceptualizesthe

interrelationshipofhealthattributesashierarchal,basedon

breadthandoncoverageofdifferentaspectsofhealth.Forexample,physicalfunction,whichisoneoftheprimary

healthattributes,hasfoursecondaryattributes,oneofwhich

isself-care.Self-caremay, inturn,bedisaggregatedinto

morespecifichealthattributes,shownasthethirdlevelof

classificationinfigure2.3.

Theestimationofhealthylifeexpectancybeginswiththe

calculationoflifetablevaluesfollowedbythecalculationof

age-specificprevalenceratesofbeinghealthyandnotbeing

healthy.Theformulasneededtocalculatethelifetable

valuesforanabridgedlifetablearesummarizedinsection

2.2.1. Tocalculatetheage-specificprevalenceratesofbeing

healthy,firstcalculatetheratesofreportingfairorpoor

health (nx).Theratesofbeinghealthy,thatis,reporting

goodorbetterhealthisthen(1nx).Thenforeachage

interval (x,x+n),theratesofbeinghealthy(1nx)aremultipliedbythetotalnumberofyearslivedwithinthe

sameageinterval (nL

x).Thiscalculationprovidesan

estimateofthetotalnumberofyearsagroupofpersonsare

expectedtoliveinahealthystateduringtheinterval.The

ageinterval (n,n+x)equals 1forsingle-yearagegroups;itequals 5 ifdatausedarein5-yearagegroupsand10for

10-yearagegroups.ThemodelusedtoestimateHLE(i.e.,

theexpectednumberofyearsingoodorbetterhealth)is

summarizedinsection2.2.2.

Healthylifeexpectancycouldbeestimatedusingavarietyofhealthattributes.Forinstance,themodelmaybe

usedtoestimatedisability-freelifeexpectancyorlife

withoutactivitylimitation,alsoreferredtoasexpectedyears

ofactivelife.Regardlessofthehealthattributechosen,the

modelusestwoseparateandindependentpartialhealth

measures:(1nx)forthemorbiditycomponentandlx and

nLx forthemortalitycomponent.

2.2TheLifeTableTechniqueThelifetable,alsoknownasthemortalitytable,isused

topresentthemostcompletestatisticaldescriptionof

mortality(3).Thelifetablealsohasbeenanimportanttoolfordemographerswhoareinterestedinestimatingthe

probabilityofmarriageandremarriage,widowhood,

orphanhood,andinmigrationandpopulationprojections(4).

Abriefsummaryofthemethodcommonlyusedtoestimate

lifetablevalues,healthylifeexpectancy,andthestandard

errorsofHLEwillbepresentedintheremainingpartsof

thischapter.Foramoredetailedexplanationofthemethod

withillustrativeexamplesandtheassociatedsensitivity

analysis,refertoHealthyPeople2010StatisticalNotes,No.21andNo.22(5,6).

2.2.1Estimatingtheaverageexpectationof lifeTheobjectiveofthelifetableistocalculatetheexpected

numberofyearslived,ifagroupofpeople,currentlyagex,

livedtherestof theirlivesexperiencingalltheage-specific

mortalityratesobservedforthepopulationataspecifictime.

Theestimationof lifetablevalues,suchastheexpectation

oflife,beginswiththecomputationofage-specificdeath

rates.Thetwosetsofdatarequiredtoconstructalifetable

arethemid-yearpopulationandthenumberofdeathsinthat

year.Thesedatacouldbeanalyzedinsingleyearsofageor

5- or10-yearagegroups.(Methodsforconstructinga

completeannuallifetablearediscussedinNCHS Vitaland

HealthStatistics,no.129.)(7)Theprocesscouldbeapplied

totheconstructionofalifetablefornational,State,orlocalpopulations.

TheestimationbeginswithcountsforthepopulationnPx

anddeathsnDx foreachagegroup.Populationcountsare

basedonmid-yearestimates.Deathsarefortheentireyear.

Theseareusedtocomputetheaveragedeathrateofeach

agegroupfortheyear (nM

x,wheren,thenumberofyearsin

theagegroup,can be 5 or 10years),as

nMx = nDx /nPx . [1]

8 Methods forCalculatingHealthyLifeExpectancy


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Thecomputedage-specificdeathratesneedtobechecked

forstability.Age-specificdeathratesareconsideredtobe

stableiftheyarebasedon20ormoredeaths.Ratesbased

onfewerthan20deathshavea relativestandarderrorof

23percentormoreandthereforeareconsideredhighly

variable.(8)

Theconditionalprobabilityofdyingwithinagivenage

groupnqx istheproportionofpeopleintheagegroupaliveatthebeginningoftheageintervalwhodiebeforereachingthenextagegroup.Whereas

nM

x isanannualdeathrate,nqxisaconditionalprobabilityofdying.Thisprobabilityis

estimatedas:

nqx= [nnMx] / [1 + n(1ax) nMx] , [2]wherea

x istheaverageproportionofyearslivedbythosewhodiedinthisageinterval.Theconditionalprobabilityof

dyingisassumedtobe1.0fortheopen,oldestageinterval.

Intheexamplepresentedhere,n is 5years,sotheprobabilitybecomes:

5qx = [55Mx] / [1 +5(1ax) 5Mx] .

Thevaluesforax areconstantsderivedfromthecompletelifetables(9).Forsingle-yearlifetablevaluecalculations, axmaybeassumedtobe.

Havingcalculatedtheconditionalprobabilityofdying,

onecannowcalculatetheprobabilityofsurvivingtoan

exactagemarkingthebeginningofaninterval.Inthelife

table,thisisexpressedasthenumberofpersonssurvivingto

anexactage(ortheexactageatthebeginningofanage

intervalwhengroupdataareused),startingwithanassumed

cohortpopulation (l0)frequentlyexpressedas100,000at

birth.Foranyotheragex,thenumberofsurvivorsatthat

agelx canbecalculated.Hence,thenumberaliveatexact

agex+n (lx+n) iscalculated bymultiplyingthenumber of

survivorsatexactagex (lx) bytheprobabilityofsurviving

fromagex toagex+n(1nqx)or:lx+n=lx(1nqx) . [3]

Thetotalnumberofperson-yearslivedfor thosepeoplewho

werealiveatthebeginningoftheageintervalx tox+n isthenthesumofthetotalnumberofyearslivedby

individualssurvivingtotheendoftheageintervalplusthe

totalnumberofyearslivedbythosewhodiedintheage

interval.Thisbecomes:

nLx=n {lx+n +ax (lxlx+n)}. [4]Intheexamplepresentedhere,n= 5so,

5Lx = 5{lx+5 + ax (lx lx+5)} .Theperson-yearsremainingforthepopulation,thatis,

Tx, issimplythe totalofalltheperson-yearsforagexand

allsubsequentagegroups,or:

Tx= nLifori=x,x+n,...,oldestagegroup. [5]Theaverageexpectedyearsperpersonisthenthetotal

person-yearsdividedbythenumberofpersonssurvivingto

thebeginningoftheageintervalx,or:

ex= Tx / lx . [6]2.2.2Estimatinghealthy lifeexpectancy

Thelifetabletechniqueis apowerful toolforestimating

theremainingyearsoflifethatagroupofpersonswould

Figure2.1.Aschematicpresentation ofthemodelSOURCE:AdaptedfromamodelbytheInstituteofMedicine,NationalAcademyofSciences,1998.

Methods forCalculatingHealthyLifeExpectancy 9


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Figure2.2.Aschematicframeworkforestimatinghealthylifeexpectancyatthenational levelusingrespondent-assessedhealthstatusasanexample

Figure2.3.ExampleofattributesforhealthclassificationsystemSOURCE:BoyleandTorrance. Developing Multi-attributeHealthIndexes. MedicalCare,1984.



19/75

expect toliveoncetheyhadreachedacertainage.Regardlessoftheirage,theremainingyearsof lifemightbelived ingoodhealthorin lessoptimalhealthstatesorsomecombinationofboth.Thetraditionallife table techniquedoesnotdistinguishbetweenremaininghealthyyearsandunhealthyyears.Additionaldataareneeded todisaggregatethe totalnumberofyearsintoexpectedyearsofhealthyandofunhealthy life.

Thetotal

number

of

expected

years

of

life

are

partitioned

intohealthyandunhealthyyearsusinghealthdata(figure2.2).Ingeneral,healthdata,collectedthroughhealthsurveysorfromclinicalobservations,areused toestimatetheprevalenceofdifferenthealthstates.Thepopulation isthenpartitionedintoproportions thatareexperiencingvaryingstatesofhealth.Thepartitionmaybeassimpleasdividing thepopulationintothosewhoarehealthyand thosewhoareunhealthy.Or,thepopulationmaybepartitionedintomore than twopopulationsubgroups,accordingtovaryingdegreesofhealth,usingmultidimensionalscaling todescribehealthstates.

TocalculateHLE,thepopulationofeachageintervalinthe lifetable ispartitionedintotheproportionexperiencinganunhealthycondition(5x)andthosethatareconsideredhealthy(1

nx).SincenLx isthe totalnumberofperson-yearslivedforthepopulation inage intervalxtox+n(equation5), theproportionof theseyears livedinahealthystate(

nL

x) isthen:

xLx=(1nx)nLx. [7]

Oneofthefollowing twoequationscanbeused todetermineHLE:

w1

e x=lx nLx.i =x [8]

orw

1e x=lx (1ni)nLi

i =x [9]where

ex isHLEatagex,orthenumberofremainingyears

ofhealthy lifeforpersonswhohavereachedagex;lx isthenumberofsurvivorsatagex;(1nx) represents theage-specificrateofbeinghealthy;nLx isthe totalnumberofyearslivedbyacohort intheageinterval(x,x+n);andw istheoldestagecategory.

Theexpectedyearsofunhealthylife isexex.However,

ifmultiplestatesofhealthstatusaredescribed,theprevalenceforeachofthosestatesforeachage intervalmustbecalculated.Equationssimilarto[8]and[9]areusedtoestimateseparatelytheexpectedyearsof lifein thosehealthstates.

2.2.3Standarderrorsofhealthy lifeexpectancyTheestimatesforage-specificprevalenceofhealthyand

unhealthystatesarederivedfromsurveysorsamples.Consequently,theseestimateshaveassociatedsamplingerror.Calculating thestandarderrorof theresultingestimatedHLEisespecially importantwhencomparingpopulationsubgroups.Thissectiondiscusses themethodofestimating thestandarderrorsofHLE,withandwithoutinformationonthesurveysampledesign.Standarderrorsfortheother lifetablevaluescanbecalculatedseparatelywhenneeded.SeeChiangandKeyfitzfordetails(10,11).

Eachage-specificvalueof theprevalenceof thepopulationexperiencinghealthylife,(1

nx), isanestimated

proportionwithanassociatedvarianceandstandarderror.Thevariancesoftheseproportionsandtheirstandarderrorsmaybeestimatedusingroutinestatisticalmethods.Consequently,thevariance(S2) isgivenbythebinomialvarianceof:

S2(nx) = [nx(1nx)]/nNx, [10]wherenNx is thenumberofpersonsin theage interval(x,x+n)ofthesamplefromwhichtheprevalencerateswerecomputed.

Thevariancesof theprevalenceratesfromequation10canbeusedtoestimate theoverallvarianceofex usingthe

followingformula:w

1VAR(ex) = 2 [nLi2S2(1ni)].lx

i =x [11]IllustrativeapplicationsofthevarianceofHLEusing1995U.S.populationdataarepresentedinHealthyPeople2010Statistical

Note

No.

21

(5).

References1. FieldMJ.GoldMR.(eds).Summarizingpopulationhealth:

Directionforthedevelopmentandapplicationofpopulationmetrics.InstituteofMedicine.Washington,D.C.:NationalAcademyPress.1998.

2. BoyleMH,TorranceGW.Developingmulti-attributehealthindexes.MedCare22(11):104557.1984.

3. PressatR.Demographicanalysis.NewYork:AldinePublishing.1961.

4. SpiegelmanM.Theversatilityofthelifetable.AmJPublicHealth47:297304.1957.

5. MollaMT,WagenerDK,MadansJH.Summarymeasuresofpopulationhealth:Methodsforcalculatinghealthylifeexpectancy.StatisticalNotes,no21.Hyattsville,Maryland:NationalCenterforHealthStatistics.August2001.

6. WagenerDK,MollaMT,CrimminsEM,PamukE,MadansJH.Summarymeasuresofpopulationhealth:AddressingthefirstgoalofHealthyPeople2010,improvinghealthexpectancy.StatisticalNotes,no22.Hyattsville,Maryland:NationalCenterforHealthStatistics.September2001.

Methods forCalculatingHealthyLifeExpectancy 11


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7. AndersonRN.MethodsforconstructingcompleteannualU.S.lifetables.NationalCenterforHealthStatistics.VitalHealthStat2(129).1999.

8. NationalCenterforHealthStatistics.VitalstatisticsoftheUnitedStates,1992,volII,mortality,partA.Washington:PublicHealthService.1996.

9. SirkenMG.Comparisonoftwomethodsofconstructingabridgedlifetablesbyreferencetoastandardtable.NationalCenterforHealthStatistics.VitalHealthStat2(4).1966.10. ChiangCL.Astochasticstudyofthelifetableanditsapplication:II.Samplevarianceoftheobservedexpectationof lifeandotherbiometricfunctions.HumBiol32:22138.1960.

11. KeyfitzN.Introductiontothemathematicsofpopulationwithrevisions.Cambridge,MA:AddisonWesley.1968.



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3. Expected Years of Healthy Life Under Various Definitions of Health

3.1 Introduction

Nosingledefinitionofthecomponentofhealthy lifeexpectancymeasures thenonfatalhealthoutcome.Prevalenceorincidenceofhealth-relatedoccurrencesarenumerousandmeasuredifferentaspectsofhealth.Theseincludeself-ratedhealthormeasuresofwork,activity,orfunctional limitations.Theycouldalsobeobservedratesorprobabilitiesoftheoccurrenceofbadphysicalormentalhealth,acuteorchronicconditions,health-relatedbehaviors,orevenhealthserviceutilization.Inthischapter,thepracticalapplicationof thecompositemeasureisillustratedbycombiningvariousnonfatalhealthoutcomemeasureswith lifetablevalues;thesecombinationsareusedtoestimateavarietyofhealthylifemeasuressuchasexpectedlife

in

good

or

better

health,

free

of

activity

limitation,

or

withoutneedinghelp inADLorIADL.

Healthy lifeexpectancywillbeestimatedfirstasexpectedyearswithouthealth-related limitation.That is,theprevalenceofactivity,work,andfunctional limitationswillbeusedasthenonfatalmeasure.Second,healthylifeexpectancyfrom theperspectiveofdiseasesorchronicconditionswillbediscussedusingtheprevalenceofchronicarthritis,heartdiseases,hypertension,anddiabetes.Prevalenceofoverweightandobesityamongadultswillbeused todiscusshealthylifeexpectancyasameasureofhealth-relatedbehavior.

Healthy lifeexpectanciesareestimatedby5-yearagegroupandsex.Estimatesarealsopresentedbyracewheneverdatabyraceareconsideredreliable.Datafromvarioussourcesareusedfortheestimates.Lifeexpectanciesby5-yearagegroup,sex,andraceareestimatedusingdatafromNCHSand theU.S.CensusBureauasdescribedinchapter2.Prevalenceratesof thevarioushealthstatesarecalculatedfromthepersonandconditionfilesofNHISfortheyears198596.3.2 Expected Years of Healthy Life for Malesand Females

Asnumerousstudieshaveshown thathealthylifeexpectanciesvaryconsiderablybothbyageandsex(14),disparitiesinhealthy lifeexpectancieswillbediscussedforsubgroupsdefinedbythesefactors.Measuresusedforthediscussionincludeexpectedyears ingoodorbetterhealth,years inexcellenthealth,yearswithoutactivitylimitation,yearswithoutwork limitation,yearswithoutlimitation inADLorIADL,andyearswithoutdiseaseorchronicconditions.

3.2.1 Expected years in good or better health

Expectedyears

of

life

is

first

measured

using

expected

yearsingoodorbetterhealth.First,respondentswhostatedthat theywere ingood,verygood,orexcellenthealthwereclassifiedaspersonsingoodorbetterhealth;respondentswhoassessedtheirhealthasfairorpoorwereconsideredpersonsinpoorhealth.Expectedyearsofhealthylifecanalsobeestimatedusingexpectedyears inexcellenthealth.Toestimateexpectedyears inexcellenthealth,respondentswereclassifieddependingonwhethertheirself-assessedhealthwasexcellent.Figure3.1presentsthedistributionofthosereportinggoodorbetterhealthby5-yearagegroupandsex.Thepercentageofthosewhowere ingoodorbetterhealthdeclineswithage,slowlyforyoungeradults,butrelativelyfasterforolderadults.Theestimatedyearsingoodorbetterhealthandinexcellenthealthforselectedagesbysexarepresentedalso intable3.1.

The tableindicatesthat in1995,anewbornbabywouldexpectto live75.8years(72.8yearsformalesand78.8yearsforfemales).Of thistotalexpectedlifespan,66.5years(87.7percent)wereexpectedtobeingoodorbetterhealth,whereasonly26.4years(34.8percent)wereexpectedtobeinexcellenthealth.Expectedyearsofhealthy life,measured inyearsaswellasapercentageof total lifeexpectancy,variesbyage.Asonegetsolder,years ingoodorbetterhealthdecreaseinbothabsoluteandrelativeterms.In1995,forexample,apersonatage20wouldexpecttospend84.3percentofhisorherfuture lifeingoodorbetterhealthandonlyabout29.0percent inexcellenthealth.Atage65, thesepercentagesdeclinedto71.0percentand14.9,respectively.

Expectedyears ingoodorbetterhealthandinexcellenthealthalsovariedbysex.Femalescouldexpect tolivemoreyearsingoodorbetterhealththan theirmalecounterparts.Ontheotherhand,malescouldexpectarelativelyhigherproportionoftheirfuture lifeingoodorbetterhealthat theyoungerageswhereasfemalesseemslightlybetteroffafterage65(figure3.2).Whenhealthy lifeismeasured in termsofexpectedyears inexcellenthealth,malesatyoungerageswouldexpecttospendmoreyearsandahigherproportionoftheir livesinexcellenthealth thanfemales.Theoppositewas trueafterage75.Thetablealsoindicatesthatas thepopulationages,thedifference inhealthylifebetweenmalesandfemalesdeclinesslightly,especiallywhenhealthy lifeismeasured inyearsratherthanasapercentof lifeexpectancy.Thedifferencebetweenexpectedyears ingoodorbetterhealthformalesandfemales isstatisticallysignificant(p


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Figure3.1.Percentageofpersonsreportinggoodorbetterhealth,byageandsex:UnitedStates,1995

3.2.2 Expected years without activity limitation

Inthe1995NHIS,respondentswereaskedaboutactivitylimitation.Respondentswerecategorizedintooneofthefollowinggroups:notlimitedinanyway;unabletoperformtheirmajoractivity;limitedeither inkind/amountof theirmajoractivity;andlimitedinactivitiesother than theoneidentifiedasthemajoractivity.Respondentswithunknownactivitylimitationstatuswereassumed tobenot limited(5).Expectedyearsofhealthy lifedefinedasdisability-free lifeexpectancy(DFLE)wereestimatedbasedontheprevalenceofmajoractivitylimitationonlyandonanytypeofactivitylimitation.Thedistributionofthosefreeofanyactivitylimitationby5-yearagegroupandsex ispresented infigure3.3.Thefigure indicatesthatactivitylimitation isafunctionofage.Thepercentageofmalesandfemaleswithoutanyactivitylimitationdeclineswithageataslowerrateat theyoungeragesandarelativelyfasterrateat theolderages.

Theexpectedyearswithoutmajoractivitylimitationandyearswithoutany limitationforselectedagesbysexispresented intable3.2andfigure3.4.Onaverage,individualsofallagescouldexpecttospendmore than4ofevery5yearswithoutlimitation intheirmajoractivity.Ababybornin1995wouldbeexpected tospendmore than94percent(94.1formalesand94.7percentforfemales)ofhisorhertotal lifeexpectancywithoutlimitation inmajoractivity.Atage65,thispercentagedroppedonlybyabout5percentagepoints to89.1percent(88.6formalesand89.5percentfor

females).Ontheotherhand,when thebroaderdefinitionofthemeasureanyactivity limitationisused, thepercentageoflifeexpected tobewithout limitationdeclinedfrom94.4to82.5percentatbirth(from94.1to83.2percentformalesandfrom94.7to81.9percentforfemales)andfrom89.1 to61.3percentatage65.

Femalescouldexpect to livemoreyearswithoutmajororanyother typeofactivity limitation.Thedifferencebetweenmalesandfemalesinexpectedyearswithoutmajor

Figure3.2.Percentageofexpected life ingoodorbetterhealthatbirth,20,and65yearsofage,bysex:UnitedStates,1995

14 ExpectedYearsofHealthyLifeUnderVariousDefinitionsofHealth


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Figure3.3.Percentagefreeofactivity limitation,byageandsex:UnitedStates,1995

activitylimitation isstatisticallysignificant(p


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Figure3.4.Percentageof lifeexpectancyfreeofanyactivitylimitationatbirth,20,and65yearsofage,bysex:UnitedStates,

food;shoppingforpersonal items;managingmoney;usingthe telephone;anddoingheavyworkaroundthehouse(5).Therecodedresponsecategorieswerepersonswhoneedthehelpofotherpersonstoperformpersonalcareneeds,thosewhoneedthehelpofotherpersonstoperformotherroutineneeds,andthosewhoarenotlimitedinperformingpersonalorroutineneeds.Thosewithunknownlimitationstatuswereassumed tobenot limited inperformingpersonalcareorotherroutineneeds.Figure3.5

presentsthepercentagedistributionof thosewhowereabletoperformpersonalcareneedsorwhowerenot limited inotherroutineneedsofdailylivingby5-yearagegroupandsex.Thedistribution indicates thatlimitation inpersonalcareorotherroutineneedsofdailylivingwasahealthproblemmostlyassociatedwitholdage.Expectedyearswithoutfunctionaldependencywerecalculated,andtheresultsforsomeselectedagesbysexarepresented in table3.4.

Accordingto

the

results

of

the

1995

NHIS

data,

those

whowereyounger thanage75couldexpect tolivemorethan90percentoftheirremaininglifewithoutfunctionaldependency.A75-year-oldmalewouldexpect toliveabout90.2percentofhis totalexpectationoflifewithoutfunctionaldependency.Thepercentagedeclined toonly88.1percentatage80.Atage75,onaverage,adultfemaleswouldexpecttolivenearly88percentof theremainderoftheirlivesfreeoffunctionaldependency.Onaverage,an80-year-oldfemalewouldexpectto live83.4percentofherlifeexpectationfreeoffunctionaldependency.

Whenyearswithout limitationweremeasuredin termsoffunctionaldependencyduetolimitationsinADLorotherroutineneeds(IADL),adultsyoungerthan65yearsofagecouldexpectto livemorethan80percentof theirexpectedlivesfreeof limitation(morethan86.5percentformalesand80.1percentforfemale).Atanygivenage,femaleswouldexpectto livemoreyearswithoutfunctionaldependencybecauseofADLorIADLlimitation.Thedifferencebetweenmalesandfemales inexpectedyearswithoutADLorIADL

Figure3.5.Percentageabletoperformpersonalcareneedsornotlimitedinotherroutineneeds,byageandsex:UnitedStates,199516 ExpectedYearsofHealthyLifeUnderVariousDefinitionsofHealth

1995


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Figure3.6.Percentageof lifeexpectancyabletoperformpersonalcareneedsornot limited inotherroutineneedsat45,65,and75yearsofage,bysex:UnitedStates,1995

limitation isstatisticallysignificant(p


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weight in thecalculationofBMIsresultsin theover-estimationofexpected lifewithBMI less than25andwithBMI lessthan30.

Thepercentageofadult lifeexpectancyexpectedtobespentwithBMI lessthan25decreasedcontinuouslywithageforyoungeradultsandthenroseat theolderages.Byage65,thepercentagewas50.4,andbyage80,itwas63.6percent.Ateachage,adultfemalesexpectedtospendalarger

share

of

their

future

years

with

aBMI

less

than

25

thandidadultmales.Atage20,forexample,whileadultfemalescouldexpect tospend57.2percentoftheiraveragelifeexpectancywithaBMI less than25;theshareofaveragelifeexpectancyforadultmalesof thesameagewasonly40percent.Atage65, thepercentageof lifeexpectancytobespentwithaBMIlessthan25rosetoabout54percentforadultfemalesbutwasexpectedtobeonly50percentforadultmales.

Thetablealsoshowsthat,onaverage,adultsaged20yearsandovercouldexpecttospendmorethanfourfifthsoftheirliveswithoutbeingobese(BMIlessthan30);theyalsocouldexpectthepercentageofremaininglifeexpectedtobespentwithoutbeingobesewouldrisewithage,forbothadultmalesandfemales.Atage20,onaverage,adultfemalescouldexpect tospend83.4percentoftheirexpectedliveswithBMIlessthan30,whileadultmalescouldexpecttospend84percentof theirremainingliveswithanaverageBMI lessthan30.Atage65, theaveragepercentageofremaining lifeexpectedtobespentwithaBMIof less than30was84.2forfemalesand88formales.Becauseoftheirhigher lifeexpectanciescompared tomalesofthesameage,adultfemalesexpected tospendmoreof theirremainingyearswithaBMIoflessthan25aswellasaBMIoflessthan30.ThedifferencebetweenmaleandfemaleexpectedyearswithBMI lessthan25andBMIlessthan30issignificant(p


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Figure3.11.Percentageingoodorbetterhealth,byageandrace:UnitedStates,1995

expectancyforawhitemale;yet,itwasonly60.1percentfora65-year-oldblackmale.

Thelasttwocolumnsofthe tableshow theracialdifferencesbothinlifeexpectancyandexpectedyears ingoodorbetterhealth.Formalesaswellasfemales, thedifferenceinyears ingoodorbetterhealth islargerthanthedifferencein

summary measures of population health,report of findings of methodologic and data issues

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