evaluating the quality of epidemiological studies

8/23/2019 Evaluating the Quality of Epidemiological Studies

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Evaluating the Quality of

Epidemiological Studies

Low Intake of Fruits, Berries and Vegetables isAssociated with Excess Mortality in Men: the KuopioIschaemic Heart Disease Risk Factor (KIHD) study


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Low Intake of Fruits,Berries and Vegetables isAssociated with ExcessMortality in Men: the

Kuopio Ischaemic HeartDisease Risk Factor(KIHD) study


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The Kuopio Ischaemic Heart Disease Risk

Factor (KIHD) study Kuopio (kw'py') The city is surrounded by

lake Kallavesi, located in CentralFinland.

Kuopio is known as a strong center ofhealth (e.g. it has the biggest yearlyenrollment rate of medical students inFinland), pharmacy, environment,food & nutrition (all legalized Clinicaland Public Health Nutritionists inFinland graduate from the University

of Eastern Finland) Finland has one of the highest

mortality rates related to CHD accdg tothe Seven Countries Study


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The Kuopio Ischaemic Heart DiseaseRisk Factor (KIHD) study

The Kuopio Ischemic Heart Disease Risk FactorStudy (KIHD) isan ongoing prospective

population-based cohort study designedtoinvestigate risk factors for cardiovasculardisease, atherosclerosis,and related outcomes inmiddle-aged men from eastern Finland, the

population with one of the highest recordedrates of CHD.The study protocol was approvedby the Research Ethics Committeeof theUniversity of Kuopio.


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ABSTRACT: The aim of this work was to assess the

association of the dietary intake of a food group

that includes fruits, berries, and vegetables withall-cause, CVD-related and non-CVD relatedmortality.

Although several prospective studies have

directly related fruits and vegetables intake toCVD, few studies have reported an associationbetween fruits and vegetables and overallmortality.


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SUBJECTS AND METHODS:

SUBJECTS: The study population comprised a random, age stratified sample of

middle aged men living in the city of Kuopio, Finland, or surrounding ruralcommunities. The men were aged 42, 48, 54, or 60 years at the baselineexamination that was carried out between March 1984 and December 1989.

All subjects gave informed consent.

A total of 2682 participants (82.9% those eligible)were enrolled in thestudy between 1984 and 1989. Because previousdisease affects the diet, menwith a prevalent CHD (n=677) wereexcluded from the main analyses. Of theremaining 2005 men,food record data were available for 1980 men.


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SUBJECTS AND

METHODS:Assessment of FoodConsumption

Dietary intake of nutrients wasassessed quantitatively witha 4-day

food recording at the KIHD baselineexaminations.

Intakeof nutrients was calculatedby use of NUTRICA version 2.5software,which uses mainly Finnishvalues of nutrient composition

offoods and takes into account foodpreparation losses of vitamins.

Intake of fruits, berries andvegetables also included jams,nectars and juices but not potato.


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OTHER MEASUREMENTSincludes:

Assessment of medical hx and

meds, family hx of diseases,smoking, alcohol consumption,and blood pressure.

Collection of blood specimens andmeasurement of maximal oxygenuptake, serum lipid, serum

lipoproteins, and 24-hr urinaryexcretion of nicotine metabolites.

Diabetes was defined. Plasma fibrinogen was also

determined.

SUBJECTS AND

METHODS:


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FOLLOW UP

EVENTS: All deathsincluded from thestudy entry toDecember 2000

were included.(12.8y follow-up)

485 all-causedeaths

245 CVD-relatedcauses

240 non-CVD-related causes

SUBJECTS AND

METHODS:


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SUBJECTS AND METHODS:STATISTICAL ANALYSIS: Data analyzed using SPSS 10.0 software. Subjects were divided into fifths for their

mean intake of fruits, berries, andvegetables. The mean of each fifth wasreported and compared by ANOVA.

Relationship between the specific groupintake with risk of mortality and survivalwere analyzed using Cox proportionalhazards model. (five

covariates were used) Correlations between cardiovascular riskfactors and dietary intake of fruits,berries and vegetables were estimated byPearsons correlation coefficient.


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RESULTS:

The daily intake of fruits, berries and vegetableswas 284182 grams (mean).

The subjects were divided into fifths of the meandaily intake, and the main characteristics of thesubjects in those categories is shown in Table1.


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RESULTS: Table 1


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RESULTS: Men in the highest fifth (highest consumption of

the food group) were younger, smoked and

drank alcohol less; have lower blood pressure,plasma fibrinogen, and LDL cholesterol; andhigher intake of fiber, vit C and E, folate, B-carotene and total energy.

Occurrences of total mortality (incld CVD andnon-CVD related) were the highest among menwith the lowest consumption of fruits andvegetables.


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RESULTS: In a Cox proportional hazards model (Table 2)

shows a significant inverse association between

the intake of fruits, berries, and vegetables andall cause, CVD- and non-CVD-related deaths.

CVD-related mortality is presented to illustratethe earlier occurrence of deaths among men in

the two lowest fifths compared to others. (Fig.1) Nutrients that were negatively associated with

all-cause mortality were vitamin C, folate, andvitamin E.


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RESULTS: Table 2


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RESULTS:Figure 1


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RESULTS: Table presents the correlation between the intake of

fruits, berries and vegetables and commoncardiovascular risk factors.

The strongest negative correlations found betweenintake of the specific food group to serumhaptoglobin and plasma fibrinogen.

Weaker negative correlation between particular

intake with age, serum total HDL and LDLcholesterol, and also diastolic and systolic bloodpressures.

Positive correlation between the maximal oxygenuptake and intake of fruits, berries and vegetables.


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RESULTS: Table 3


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DISCUSSION: The authors of the study stated that Our results provide

further evidence for the hypothesis that a high intake offruits, berries, and vegetable is associated with reduced

risk of mortality. The proposed beneficial substances from the food group

include antioxidant vitamins, folate, fiber, potassium,and magnesium. Low contents of fat, energy and sodiummay reduce in part the risk of obesity and high blood

pressure. Advantages and disadvantages of using the 4 day FoodRecord.

Men who consumed more plant products seemed to havea healthier lifestyle compared to men who consumed

less.


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CONCLUSION OF THE STUDY: In conclusion, the findings of this prospective

cohort study indicate that a higher intake of

fruits, berries and vegetables is associated with areduced risk of CVD-related, non-CVD relatedand overall mortality in middle-aged men inEastern Finland. Our findings provide furtheradditional evidence that higher intakes of fruitand vegetable can prevent heart diseases andmortality.


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Low Intake of Fruits, Berries and Vegetables isAssociated with Excess Mortality in Men: the Kuopio

Ischaemic Heart Disease Risk Factor (KIHD) study


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AS A COHORT STUDY:


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Yes, a large number of participants were included inthe baseline study, a total of 2,682.

CVD-related mortality: 1,950 menAll-cause and non-CVD related mortality: 2,641 men

Yes, 12.8 y follow up. Yes, for this follow up study it defined the baseline

characteristics of the 2641 study participants in thefifths of intake and grouped the incidence of death inthree: all-cause death, CVD-related and non-CVDrelated.

Exposure: Advantages and Disadvantages of FoodRecordOutcome: The study used three types of statistical testto analyzed data: ANOVA, Cox Proportional hazardmodel, and Pearsons Correlation Coefficient.

No, follow up was done regarding dietary food recordafter a few years from the baseline.


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No losses to follow up. I think it was able to include in its data collection some

confounding variables like age, alcohol intake, smoking,and family history of heart disease. It also excludedsubjects with CVD history in analyzing CVD relateddeaths. For all cause mortality and non CVD relateddeaths there may be other confounding variables(eventhough Cox model made adjustments for age andexamination years).

Yes, although study is not particular only about thedevelopment of disease but also on the mortality rate.

Mortality rate: Deaths were ascertained by a computerlinkage to the national death registry using Finnish Social

Security number. There were no losses to follow up. Alldeaths that occurred from the study entry to December 31,2000, were included.

Biological samples collected but storage form notdiscussed.


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Strengths and Weaknesses of the Study:

Strengths: Weaknesses:

Large number of subjects and

longer time span Has established a baselineinformationrecorded/eliminate recall bias

Was able to measure multipleoutcomes

Establish time sequence forpossible causality

Can adjust for confoundingvariables

Was able to calculate risk

No follow up data on food

consumption (may changeover time)

Some confounding variablesfor example: accuracy of causeof death recording maybe

questionable. Further studies may be needed

to establish causation.


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Elisha Gay C. Hidalgo, RND

evaluating the quality of epidemiological studies

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