Studies on Validity and Reproducibility of Semi-quantitative Food Frequency Questionnaire for a local Community

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Long-term usual or average intakes of individual foods can be estimated by Food Frequency Questionnaire (FFQ). FFQ is useful in epidemiological studies such as an investigation of the relationship between diet and chronic disease. Several FFQs have been developed during the last two decades and used in cohort studies in Japan, but the validity was not high as FFQs in Europe and the United States. Because of the local characteristics in food intakes, we have developed a new 165 item semi-quantitative FFQ for a local community in the Department of Epidemiology, National Institute for Longevity Sciences in 2003. Validity of this FFQ was higher than those of existing FFQs in Japan and the validity was almost equal to those in Europe and the United States in a short-term study, nonetheless. We examined long-term validity and reproducibility of the FFQ in 37 nutrients by comparing between five FFQs in every three months and 12-day dietary records (12DR: 3 days×4 seasons). Furthermore, we examined seasonal differences of the dietary records. Median correlation coefficients of nutrients between each FFQ and 12DR adjusted for energy and de-attenuated ranged from 0.45-0.52 (median 0.50 of all 5 times). Median correlation coefficient between the 1stFFQ and each FFQ ranged 0.50-0.63 (median 0.60 of all 4 times). This was the highest validity and reproducibility among the conventional FFQs. Seasonal variability in food intakes in Japan was also confirmed in this study. As the long-term efficacy of this FFQ has been proved, we can use this FFQ in future large-scale cohort studies as complementary tool of DR for the assessment of nutrition and food intakes.