Gaps in epidemiologic research methods: design considerations for studies that use food-frequency questionnaires

Area of Science:

• Epidemiology
• Nutritional Science
• Dietary Assessment

Background:

• Semi-quantitative food-frequency questionnaires (FFQs) are widely used in analytic epidemiology for assessing diet and disease relationships due to their cost-effectiveness and focus on usual intake.
• However, the variability in nutrient intake estimates derived from FFQs is not well understood, and these methods do not provide precise quantitative nutrient intake data.
• Limitations in current FFQ methodology suggest that improvements alone are unlikely to fully address these issues.

Purpose of the Study:

• To highlight the limitations of semi-quantitative food-frequency questionnaires in dietary assessment for epidemiologic studies.
• To propose the inclusion of dietary standardization substudies to enhance the accuracy of nutrient intake estimation.
• To suggest optimizing other study design elements to increase the informativeness of epidemiologic research on diet and disease.

Main Methods:

• Recommends incorporating a dietary standardization substudy within larger food-frequency questionnaire studies.
• This substudy involves collecting multiple days of detailed dietary intake data (e.g., diet recalls or records) from a sample of participants.
• Emphasizes the importance of careful study population selection to maximize contrasts in dietary exposures.

Main Results:

• Dietary standardization substudies provide data for quantitative calibration of nutrient intake estimates derived from FFQs.
• These substudies enable the adjustment of risk estimates for dietary measurement error, leading to more accurate conclusions.
• Optimizing study design elements, beyond dietary assessment methods, can significantly enhance the power and validity of epidemiologic findings.

Conclusions:

• Studies utilizing food-frequency questionnaires should integrate dietary standardization substudies to improve the reliability of nutrient intake data.
• Quantitative calibration and measurement error adjustment are crucial for robust epidemiologic findings on diet and disease.
• Attention to overall study design, including participant selection, is essential for maximizing the informativeness of dietary epidemiology research.