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Differences in precision of dietary estimates among different population subgroups
S Wassertheil-Smoller1, B R Davis, B Breuer
1Albert Einstein College of Medicine, Bronx, NY 10461.
Annals of Epidemiology
|November 1, 1993
Summary
Dietary intake precision varies significantly across populations and nutrients. Understanding the ratio of intraindividual to interindividual variances is crucial for accurate nutritional studies and sample size calculations.
Area of Science:
- Nutritional epidemiology
- Biostatistics
Background:
- Dietary intake consistency varies among populations.
- Estimating nutrient intake precision (E) depends on variance ratios (R) and recorded days (k).
Purpose of the Study:
- To analyze baseline data from the Trial of Antihypertensive Interventions and Management (TAIM) study.
- To investigate variations in R among demographic groups and nutrients.
- To assess implications for correlation estimates and power calculations in nutritional studies.
Main Methods:
- Utilized baseline data from 872 participants in the TAIM trial.
- Calculated intraindividual and interindividual variances for different groups and nutrients.
- Provided methods for calculating E, determining k, and sample sizes.
Main Results:
- Demonstrated wide variation in R across demographic groups and nutrients.
- Highlighted differential requirements for dietary records to achieve precision (e.g., 7 days for NY whites vs. 2 days for AL whites for sodium-blood pressure correlation).
- Presented tables detailing within- and between-person variances.
Conclusions:
- Variations in R necessitate tailored approaches for designing nutritional epidemiologic studies.
- Accurate determination of k and sample size requires considering subgroup and nutrient-specific variance ratios.
- Optimizing study design enhances the reliability of nutrient-health outcome correlations and group comparisons.