ganizations would provide the basic munici-pal grid information, the core of the effort.Information volunteers and public safetyagencies would update the system once adisaster strikes.

Unlike the 911 system, the 711 systemwould not be a one-way, top-down commu-

It is both extraordinary and unfortunatethat at the end of the 20th century, theinternational public health communitydoes not routinely quantify or project thehealth problems of populations. There areno standardized compilations of comparableinformation on the extent of morbidity,disability, or death in different populationsof the world. Information at a global orregional level on behaviors and exposuresthat are important risk factors for deathand disability is also extremely limited.Although the demographic communityroutinely publishes projections of fertilityand population, future trends have beenprojected for only a very limited numberof causes of death [such as the humanimmunodeficiency virus (HIV)] in select-ed populations.

All too often, health statistics are provid-ed to decision-makers, the scientific commu-nity, and the public by advocates. Theseadvocates, although well intentioned, havespecific agendas, and the information theyprovide is often filtered or biased. Healthproblems without vocal advocates are fre-quently ignored until someone or somegroup "discovers" or "rediscovers" a problemor when policy neglect leads to crises inwhich the public demands action. The redis-covery of the global tuberculosis problem is aclassic example (1). Poor information on ahealth problem is often interpreted in policydebates to mean that a problem is unimpor-tant, which generates a self-perpetuatingphenomenon. In this environment, it ishardly surprising that a number of healthprograms at international organizations em-ploy their own media consultants or full-

nications system, but rather a genuine in-teractive and horizontal communicationsmedium connecting affected citizens, theirloved ones, and rescue efforts. The technol-ogy is available and affordable; the user baseis strong and growing; and the time is hereand now.

time "advocacy officers." Public health pol-icy formulation desperately needs indepen-dent, objective information on the magni-tude of health problems and their likelytrends, based on standard units of measure-ment and comparable methods. (In this case,we are defining health problems broadly toinclude diseases, injuries, and exposures toimportant risk factors.)

The Global Burden ofDisease Study

A major effort to foster an independent,evidence-based approach to public healthpolicy formulation is the Global Burden ofDisease Study (GBD). This study was initi-ated in 1992 at the request of the WorldBank; over the past 4.5 years, the work hasbeen undertaken with the full collaborationand participation of the World Health Or-ganization (WHO) (2). Final results arenow available. The study had four specificobjectives: (i) to develop internally consis-tent estimates of mortality from 107 majorcauses of death, disaggregated by age andsex, for the world and eight geographicregions; (ii) to develop internally consistentestimates of the incidence, prevalence, du-ration, and case-fatality for 483 disablingsequelae resulting from the above causes,disaggregated by age, sex, and region; (iii)to estimate the fraction of mortality anddisability attributable to 10 major risk fac-tors, disaggregated by age, sex, and region;and (iv) to develop projection scenarios ofmortality and disability, disaggregated bycause, age, sex, and region. The study isbased on the collaboration of over 100 sci-entists from more than 20 countries (3).

Just under 50.5 million individuals diedin 1990 worldwide, and the results of med-ical certification of the cause of death wereobtained for 13.8 million of these individ-uals (4). Even in cases where medically

certified causes of death are available, aseries of analyses has been undertaken toadjust for miscoding of cardiovascular, inju-ry, and other deaths. In some cases, thesecorrections for miscoding substantially alterthe estimated death rates (for example, aftercorrecting for coding of cardiovasculardeaths in Japan that had been assigned tovarious ill-defined categories, the death ratefrom ischemic heart disease increased by afactor of 2.8). To ascertain the causes ofdeath for the remaining 70 percent ofdeaths in the world, a variety of methodsand sources has been used, including sampleregistration systems in China and rural In-dia; small population laboratory studies insub-Saharan Africa and Asia; estimatesbased on epidemiologic studies of the inci-dence, prevalence, and case-fatality rates ofparticular diseases; and, as a last resort,models relating cause-specific mortality foran age-sex group to mortality from all caus-es in that age group.

For each disease and its sequelae, epide-miological estimates based on a metasyn-thesis of published and unpublished studieshave been developed. For example, esti-mates of incidence, prevalence, and dura-tion for five sequelae of diabetes were de-veloped: diabetes itself, retinopathy, neu-ropathy, amputation, and diabetic foot. In-ternally consistent estimates of incidence,prevalence, case-fatality, remission, andmortality rates and of duration were devel-oped with the aid of computer models (5).

To foster comparisons across conditionsand risk factors, a composite measure of theburden of each health problem has beendeveloped: the Disability-Adjusted LifeYear (DALY) (6). DALYs from a conditionare the sum of years of life lost because ofpremature mortality and years of life livedwith disability, adjusted for the severity ofdisability. Time lived with various short-,medium-, and long-term disabilities isweighted by a severity weight that is basedon the measurement of social preferencesfor time lived in various health states (7).

Selected Findings of the GBD

Diseases and injuries in the GBD were di-vided into three clusters: Group I, consist-ing of communicable diseases, maternalcauses, conditions arising in the perinatalperiod, and nutritional deficiencies; GroupII, encompassing the noncommunicablediseases; and Group III, comprising all in-juries, whether intentional or unintentional(Table 1). Group I causes of death consist ofthe cluster of conditions whose prevalencedeclines at a faster rate than mean mortalityrates [most developed and a number of de-veloping countries have undergone demo-graphic and "epidemiological transitions" to

SCIENCE * VOL. 274 * 1 NOVEMBER 1996

Evidence-Based HealthPolicy-Lessons from the Global

Burden of Disease StudyChristopher J. L. Murray and Alan D. Lopez

C. J. L. Murray is an associate professor at the Burden ofDisease Unit of the Harvard School of Public Health, 9Bow Street, Cambridge, MA 02138, USA. A. D. Lopez isa scientist at the World Health Organization, Geneva CH-121 1, Switzerland. The authors alone are responsible forthe views expressed here.

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lower fertility and mortality rates duringthis century (8)]. As a result, in low-mor-tality populations, these causes account foronly a small proportion of deaths (and,conversely, dominate the cause-of-deathpattern in high-mortality populations). Thenoncommunicable diseases listed togetherin Group II are the most important healthproblems in populations that have under-gone or almost completed the epidemiolog-ical transition. Injuries are classified sepa-rately in Group III.

Globally, one-third of deaths arise fromone of the diseases in Group I (Table 1).One death in 10 is caused by an injury, andjust slightly more than 1 death in 2 isattributable to Group II, the noncommuni-cable diseases. Because of differences inpopulation age-structure, mortality rates,and epidemiologic patterns, there is a dra-matic difference in the distribution ofdeaths between established market econo-mies (EMEs) and the formerly socialisteconomies of Europe (FSEs) and the devel-oping regions. For the developing regions asa whole, Group I conditions account for 4out of every 10 deaths, Group II conditionsfor 1 death in 2, and injuries (Group III) for1 death in 10. For countries in EMEs andFSEs, only 1 death in 16 is due to Group Idiseases, whereas Group II accounts for over85% of all deaths. Variation in the extent ofthe demographic and epidemiological tran-sitions in the developing regions is evidentfrom Table 1. In sub-Saharan Africa, GroupI diseases account for 65% of all deaths,

Table 1. Distribution of deaths (in thousands) bybroad-cause group and region in 1990. Theseregions and their abbreviations are as follows:established market economies (EMEs), the for-merly socialist economies of Europe (FSEs), Lat-in America and the Caribbean (LAC), China(CHN), India (IND), other Asia and islands (OAI),Middle Eastern Crescent (which includes NorthAfrica, the Middle East, Pakistan, and the Cen-tral Asian Republics of the former Soviet Union)(MEC), and sub-Saharan Africa (SSA). The crite-ria used to define these regions included thelevel of socioeconomic development, epidemio-logic homogeneity, and geographic contiguity."Developed" includes EMEs and FSEs; "devel-oping" includes the other six regions.

Region Group Group 11 Group III Total

EMEs 453 6,223 445 7,121FSEs 214 3,188 389 3,791IND 4,775 3,788 808 9,371CHN 1,405 6,460 1,020 8,885OAI 2,190 2,785 559 5,534SSA 5,316 1,864 1,022 8,202LAC 943 1,676 389 3,009MEC 1,945 2,156 452 4,553World 17,241 28,141 5,084 50,467Developing 16,573 18,730 4,251 39,554Developed 667 9,41 1 834 10,912

whereas in China these diseases account foronly 16% of deaths.

The three leading causes of DALYs in1990 were lower respiratory infections, di-arrheal diseases, and conditions arising dur-ing the perinatal period (low birthweightand birth asphyxia or birth trauma) (Table2). Tuberculosis, measles, and congenitalanomalies are also among the 10 leadingcauses of DALYs worldwide. Perhaps moresurprisingly, unipolar major depression,ischemic heart disease, and cerebrovasculardisease are ranked fourth, fifth, and sixth,respectively. Road traffic accidents are alsoamong the 10 leading causes of DALYs onthe global list, accounting for 2.4% of allDALYs. Switching to a perspective thatcaptures the effects of nonfatal health out-comes emphasizes the role of a number ofneuropsychiatric conditions as contributorsto the burden of disease. For example, alco-hol dependence ranks 20th as a cause ofglobal DALYs, bipolar disorder ranks 22nd,and schizophrenia ranks 26th.

To guide current investment decisions(including investments in health research,human resource development, and physicalinfrastructure), three different mortality anddisability scenarios have been projected from1990 to 2020 (4). The projection model isbased on the observed relation betweencause-specific mortality and socioeconomic

variables, including income per capita, aver-age years of schooling, time, and tobacco use.Three sets of projections of these indepen-dent variables form the basis of the baseline,pessimistic, and optimistic scenarios present-ed in the GBD. The range defined by thepessimistic and optimistic projections is nota formal confidence interval but does pro-vide some qualitative sense of the uncertain-ty associated with the projections of differentconditions. From 1990 to 2020, the baselineprojection scenario suggests that the follow-ing causes will rise in the rankings: ischemicheart disease, unipolar major depression, ce-rebrovascular disease, chronic obstructivepulmonary disease, HIV, war, violence, sui-cide, and lung cancer. These changes arelargely due to demographic shifts and trendsin age-specific mortality rates in a large partcaused by the epidemic of tobacco-relateddiseases (9). Major declines in relative rankare expected for lower respiratory infections,diarrheal diseases, measles, malaria, anemia,and protein-energy malnutrition. In the pes-simistic scenario, major Group I conditionssuch as lower respiratory infections and diar-rheal diseases remain much larger causes inabsolute terms but nonetheless still fall sub-stantially in the relative rankings.

Some diseases or injuries occur withoutprior exposure to health hazards. Many cases,however, are attributable to one or more risk

Table 2. The 17 leading causes of DALYs in the world in 1990 and 2020, plus those ranked 19th, 28th,and 33rd, according to the baseline scenario. The projections are based on a simple model that hasbeen developed relating cause-specific mortality rates to income per capita, average years of schooling,time (serving as a proxy for technology change), and tobacco use. Cause-of-death data from 47countries for the period 1950 to 1990 have been used to fit log-log regression equations. The projec-tions from the former WHO Global Programme on AIDS were used for HIV. DALYs were projected withthe use of simple relational models between death and disability.

1990 2020 baselinescenario

Disease or injury Percent of Percent of

Rank total Rank totalDALYs DALYs

Lower respiratory infections 1 8.2 6 3.1Diarrheal diseases 2 7.2 9 2.7Conditions arising during the perinatal period 3 6.7 11 2.5Unipolar major depression 4 3.7 2 5.7Ischemic heart disease 5 3.4 1 5.9Cerebrovascular disease 6 2.8 4 4.4Tuberculosis 7 2.8 7 3.1Measles 8 2.6 25 1.1Road traffic accidents 9 2.5 3 5.1Congenital anomalies 10 2.4 13 2.2Malaria 11 2.3 24 1.1Chronic obstructive pulmonary disease 12 2.1 5 4.1Falls 13 1.9 19 1.5Iron-deficiency anemia 14 1.8 39 0.5Protein-energy malnutrition 15 1.5 37 0.6War 16 1.5 8 3.0Self-inflicted injuries 17 1.4 14 1.9Violence 19 1.3 12 2.3HIV 28 0.8 10 2.6Trachea, bronchus, and lung cancers 33 0.6 15 1.8

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factors. Mortality and disability attributableto 10 major risk factors have been estimatedin the GBD and are summarized in Table 3.Exposures that underlie the major infectionsof young children, such as malnutrition andpoor water, sanitation, and hygiene, cause anestimated 20 to 25% of the total disease andinjury burden. Their control remains a pri-ority for global public health. Various expo-sures such as tobacco use, alcohol use, andoccupation each account for approximately3% of the burden, which is similar to that ofmeasles, tuberculosis, and malaria. If theserisk factor estimates of burden are correct,they would suggest that the prevention ofoccupation, tobacco, and alcohol-related ill-ness and death are urgent priorities for publichealth policy. The estimates for alcohol al-low for probable cardioprotective effects andindicate a higher percentage contribution toDALYs (3.5%) than deaths (1.5%), reflect-ing the importance of disability caused byalcohol and the much younger age distribu-tion of deaths caused by alcohol than thosefrom ischemic heart disease deaths avoidedby its use. To many, it may be surprising thatthe global burden of disease attributable tophysical inactivity is nearly equal to theburden of hypertension-for both, the bur-den attributable in EMEs is much higherthan elsewhere (4.8 and 3.9%, respectively).

Figure 1 illustrates the projected trendsin burden from diarrheal diseases, HIV, andtobacco in the baseline scenario. In thisscenario, the dramatic rise of HIV as a causeof mortality and disability is clear. HIV,which in 1990 ranked 28th as a cause ofburden, would become one of the 10 lead-ing causes of DALYs early in the next de-cade, after which its incidence is projectedto decline worldwide. The magnitude of theHIV epidemic is clearly highly uncertain,depending not only on current epidemio-logic trends but on the individual, commu-nity, and government response to the epi-

demic in different countries. In the pessi-mistic scenario, the projected burden ofHIV is 51 million DALYs, and in the opti-mistic scenario it is 23 million DALYs.Because of expected economic growth andaging populations in many regions, Group Iconditions such as diarrhea are expected todecline in importance as causes of burden.In the pessimistic scenario, the burden ofdiarrhea will remain much higher, 70 mil-lion DALYs in 2020. The most dramaticfeature of Fig. 1 is the unprecedented rise inthe burden attributable to tobacco. Thistrend is a robust prediction because most ofthe tobacco-related mortality and disabilityin 2020 is due to smoking prevalence today.By 2020, tobacco is projected to account for9% of the burden expected to occur in thatyear and is expected to be the leading causeof DALYs. Of the projected 8.4 milliontobacco-related deaths, 6.0 million are pro-jected to be in developing regions overall,including 2.2 million in China, 1.5 millionin India, and 0.8 million in the MiddleEastern Crescent.

Policy Implications

A number of conclusions emerge from theresults of the GBD. First, because of expect-ed economic growth and demographicchange, the epidemiological transition iswell under way in developing regions. Al-though a number of infectious and parasiticdiseases, such as tuberculosis and malaria,are likely to remain major health challeng-es, many developing regions are alreadyfaced with the problems of responding to alarge burden of noncommunicable condi-tions and injuries. These combined demo-graphic and epidemiological trends will in-creasingly shift the focus of policy debateand research to the adult health agenda. Yetresearch on policies targeting the health ofadults in developing countries is extremely

Table 3. The global burden of disease and injury attributable to selected risk factors in 1990 (12). Burdenattributable to occupation has been estimated largely on the basis of occupational injury and diseaseregistries maintained in some countries. For the other risk factors, the attributable burden has beenestimated by analysis of relative risks from cohort studies in developed countries and by various typesof measures of the prevalence of exposure in each age-sex group in each region.

Dets Percent DYs PercentRisk factor (DXh3) of total (DALY) of total(l0) deaths (l0) DALYs

Malnutrition 5881 11.7 219.6 15.9Poor water supply, sanitation, and hygiene 2668 5.3 93.4 6.8Unsafe sex 1095 2.2 48.7 3.5Tobacco use 3038 6.0 36.2 2.6Alcohol use 774 1.5 47.7 3.5Occupation 1129 2.2 37.9 2.7Hypertension 2918 5.8 19.1 1.4Physical inactivity 1991 3.9 13.7 1.0Illicit drug use 100 0.2 8.5 0.6Air pollution 568 1.1 7.3 0.5

limited (10). Some studies have examinedthe cost-effectiveness of various interven-tion options, but much more informationon the cost-effectiveness of available pre-ventive, rehabilitative, and curative inter-ventions is required (11). Studies of inter-ventions aimed at risk factor modification,treatment, and prevention of mental healthconditions, as well as prevention, treat-ment, and rehabilitation of injuries are ma-jor priorities.

Three specific conclusions are worthemphasizing. When the burden of nonfatalhealth outcomes is included, our perceptionof priorities changes. The importance ofdisabling conditions is perhaps best illus-trated by unipolar major depression, whichranks as the fourth most important cause ofburden in 1990 and is likely to rise tosecond in 2020. The rise in unipolar majordepression and other neuropsychiatric con-ditions as causes of burden is entirely due todemographic changes, as the age-specificrates of these conditions are projected toremain constant. Injuries, both intentionaland unintentional, are also expected to be-come increasingly important causes of bur-den because of the dramatic growth expect-ed to occur in the young adult populationwho have the greatest risk of injuries, eventhough age-specific death and disabilityrates from injuries may be declining. Final-ly, the extraordinary epidemic of tobacco-related mortality and disability (over 8 mil-lion deaths in 2020 due to tobacco) emergesas the most alarming trend over the nextthree decades.

Evidence-based health policy formula-tion would require regular updates of globaland regional information (perhaps every 3to 5 years) and equivalent information atthe national and subnational levels. Effortsto address the latter are under way; morethan 30 countries, including the UnitedStates, are applying the approach outlinedin the GBD to national health problemassessment. Planning for future global and

Year

Fig. 1. DALYs attributable to diarrhea, HIV, andtobacco from 1990 to 2020, according to thebaseline projection scenario. See the text for op-timistic and pessimistic scenario projections forHIV and diarrhea.

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regional assessments has not begun. A num-

ber of factors would be important ingredientsfor successful future iterations: an environ-ment where the objective analysis of healthproblems can be fostered; widespread partic-ipation of epidemiologists and public healthexperts from many institutions and coun-

tries; sufficient time and resources to embarkon the detailed analyses that are often re-

quired to develop intemally consistent epi-demiological profiles of health problems; andclose links to the research community so

that methodological developments and re-

finements continue and are incorporated ina timely fashion. The unique collaborationof the World Bank and WHO was critical tothe success of the GBD. Similar collabora-tion and leadership will surely be needed ifthe health policy debates of the future are tobe routinely and effectively informed by theavailable evidence on health problems andpossibilities for intervention.

REFERENCES AND NOTES

1. Interest in tuberculosis had waned to an historic lowin the mid-1980s, but a series of analyses stimulatedby the World Bank as part of their Health SectorPriorities Review [for example, see C. J. L. Murray, K.Styblo, A. Rouillon, Bull. IUATLD 65, 2 (1990); C. J. L.Murray et al., Lancet 338, 1305 (1991)], the risingcase numbers of tuberculosis in developed nations,and the interaction between HIV and tuberculosis ledto tuberculosis being declared a global emergencyby WHO.

2. Preliminary results from the GBD were published inbrief in the World Development Report 1993: Invest-ing in Health (Oxford Univ. Press, New York, 1993)and more extensively in 1994 [C. J. L. Murray, Bull.WHO 72, 429 (1994); and A. D. Lopez, ibid.,p. 447; ibid., p. 481; C. J. L. Murray et al., ibid., p.495]. The complete details on the methods and finalresults are being published in a 10-volume series.The first two volumes of this series, which provide anoverview of the study, have been published: C. J. L.Murray and A. D. Lopez, Eds., The Global Burden ofDisease, vol. I: A Comprehensive Assessment ofMortality and Disability from Diseases, Injuries, andRisk Factors in 1990 and Projected to 2020 (HarvardUniv. Press, Cambridge, MA, 1996) and The GlobalBurden of Disease, vol. II: Global Health Statistics: A,Compendium of Incidence, Prevalence, andlMortal-ity Estimates for Over 200 Conditions (Harvard Univ.Press, Cambridge, MA, 1996).

3. For each disease or injury, experts (or groups ofexperts in some cases) collaborated on the study.These experts were drawn from WHO; the WorldBank; the U.S. Centers for Disease Control and Pre-vention; and academic institutions in many countries,including the United States, the United Kingdom,France, Mexico, New Zealand, Japan, India, SriLanka, China, and South Africa. Volumes IlIl through

X of the Global Burden of Disease and Injury Series,[C. J. L. Murray and A. D. Lopez, Eds. (Harvard Univ.Press, Cambridge, MA, 1996)] provide a series ofdisease-, injury-, and risk factor-specific chaptersauthored by these collaborators. In addition, a num-ber of other individuals have provided critical input tothe study (see the acknowledgments in the series.)

4. C. J. L. Murray and A. D. Lopez, in The Global Bur-den ofDisease, C. J. L. Murray and A. D. Lopez, Eds.(Harvard Univ. Press, Cambridge, MA, 1996), vol. 1,pp. 325-396.

5. A computer program, DisMod, was developed spe-cifically for the GBD to facilitate the analysis of inter-nal consistency. In this program, the user inputs a setof age-specific incidence, remission, and case-fatal-ity rates, and the program calculates the expectedduration and prevalence and death rates in a stablepopulation. Further information on the currently avail-able versions of this software can be obtained athttp://www.hsph.harvard.edu/organizations/bdu orby contacting the authors.

6. DALYs can be considered a standardized form ofquality-adjusted life years (QALYs). For useful dis-cussions of the strengths, limitations, and uses ofQALYs, see M. C. Weinstein, Int. J. Tech. Assess.Health Care 6,93 (1990); E. Nord, Soc. Sci. Med. 41,1429 (1992); J. Richardson, ibid. 39, 7 (1994).

7. DALYs are the combination of years of life lost due topremature mortality (YLLs) and years of life lived withdisability adjusted for the severity of disability (YLDs).The duration of life lost due to a death at each age inYLLs is calculated by means of a standard life tablebased on the Coale and Demeny model life tableWest with an expectation of life at birth for females of82.5 years and for males of 80 years. Time lived atdifferent ages has been valued with an exponentialfunction of the form Cxe- tx (where C is a constant, xis age, and ,B is 0.04) to reflect the greater social roleplayed by adults in caring and providing for the youngand the old. Time lost due to premature mortality hasbeen discounted at 3%, so that a year of life lost inthe future is less valuable than a year of life lost today.Years Lived with Disability (YLDs) are time lived inhealth states worse than perfect health, weighted bya severity weight for each health state. The severityweights range from 0 (which is perfect health) to 1(which is the weight for a health state equivalent todeath). The preferences of groups of individuals fordifferent health states have been measured by theperson trade-off (PTO) method. In the most simpleform of a PTO, a person is offered two alternatives.Alternative 1 is to extend life forx individuals in normalhealth, and alternative 2 is to extend life for y individ-uals in health state i. The term y is varied until therespondent is indifferent to the choice between thetwo alternatives, at which point the preference forstate i is

(1--)y

Other forms of PTOs can be structured in whichpeople are asked to trade off restoring health to xindividuals in health state i versus extending life for yhealthy individuals for a fixed period of time. Severityweights for 22 indicator conditions have been devel-oped with the PTO method applied to a group thatwas representative of each region of the world, con-vened at WHO. Very similar results have been foundin eight other preference measurement exercises in

other countries with the same PTO protocol. On thebasis of the disability severity weights for the 22indicator conditions, seven classes of disability havebeen defined, so that each class of disability containstwo to three indicator conditions. For each of theremaining several hundred disabling sequelae in-cluded in the study, the group convened at WHOselected the distribution of severity across the sevenclasses for both treated and untreated forms of thecondition. Time lived with disability is also age-weighted and discounted in the same manner asYLLs. For a complete discussion of various methodsto measure preferences for living with various healthconditions and the methods used to apply the PTOmethod in the GBD, see C. J. L. Murray, in TheGlobal Burden of Disease, C. J. L. Murray and A. D.Lopez, Eds. (Harvard Univ. Press, Cambridge, MA,1996), vol. 1, pp. 22-43; ibid., pp. 90-98.

8. The term "demographic transition" is often used todescribe the decline in fertility and mortality ratesthat most developed and a number of developingcountries have undergone during this century. Om-ran [Millbank Mem. Fund Q. 49, 509 (1971)] coinedthe term "epidemiological transition" to refer to thecharacteristic shift in the composition of causes ofdeath from infectious and parasitic to noncommu-nicable diseases. More recently, J. Frenk et al.[Health Policy Planning 4, 29 (1989)] have used the"health transition" to refer to the changes in fertility,mortality, cause of death composition, disability,and the health care system's response to thesetrends. We use "demographic transition" to refer tothe characteristic changes in fertility and mortalityrates that accompany development, and "epidemi-ological transition" to refer to changes in the age-specific mortality and disability rates that may ac-company development.

9. The impressive rise in the burden associated withneuropsychiatric conditions is exclusively due to theprojected increase in the number of young and mid-dle-aged adults who are at the highest risk of theseconditions. As a result of past changes in fertility, thenumber of children under age 5 in the developingworld will increase from 1990 to 2020 by 25% andthe number of adults between ages 45 and 59 willincrease by 140%. We were unable to find convinc-ing evidence concerning the trends or determinantsof trends in the age-specific rates of most neuropsy-chiatric conditions. We have therefore assumed formany of these conditions that age-specific incidencerates will remain constant. Some may argue persua-sively that these estimates are conservative, as anumber of socioeconomic developments may con-tribute to higher rates of mental illness; for example,the higher rates of war experienced in recent yearsmay contribute to higher rates of post-traumaticstress disorder in the coming decades.

10. R. G. A. Feachem et al., The Health of Adults in theDeveloping World (Oxford Univ. Press, New York,1992) is one of the few examples of such research.

11. D. T. Jamison et al., Disease Control Priorities inDeveloping Countries (Oxford Univ. Press, NewYork, 1993).

12. For a review of these 10 studies, see C. J. L. Murrayand A. D. Lopez, in The Global Burden ofDisease, C.J. L. Murray and A. D. Lopez, Eds. (Harvard Univ.Press, Cambridge, MA, 1996), pp. 295-324. Morecomplete discussions of methods and results areprovided in chapters on each specific risk factor.

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