a1 Division of Epidemiology, Department of Public Health and Forensic Medicine, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan
a2 Department of Environmental Health, Miyagi University of Education, Sendai, Japan
a3 School of Nursing, Miyagi University, Sendai, Japan
a4 Faculty of Human Sciences, Sendai Shirayuri Women's College, Sendai, Japan
a5 Faculty of Human Life and Environmental Science, Kochi State Women's University, Sendai, Japan
Objectives: To examine the validity and reproducibility of a self-administered food-frequency questionnaire (FFQ) used for two cohort studies in Japan.
Design: Cross-sectional study.
Setting: Two rural towns in the Miyagi Prefecture, in north-eastern Japan.
Subjects: Fifty-five men and 58 women.
Results: A 40-item FFQ was administered twice, 1 year apart. In the mean time, four 3-day diet records (DRs) were collected in four seasons within the year. We calculated daily consumption of total energy and 15 nutrients, 40 food items and nine food groups from the FFQs and the DRs. We computed Spearman correlation coefficients between the FFQs and the DRs. With adjustment for age, total energy and deattenuation for measurement error with the DRs, the correlation coefficients for nutrient intakes ranged from 0.25 to 0.58 in men and from 0.30 to 0.69 in women, with median of 0.43 and 0.43, respectively. Median (range) of the correlation coefficients was 0.35 (−0.30 to 0.72) in men and 0.34 (−0.06 to 0.75) in women for food items and 0.60 (−0.10 to 0.76) and 0.51 (0.28–0.70) for food groups, respectively. Median (range) of the correlation coefficients for the two FFQs administered 1 year apart was 0.49 (0.31–0.71) in men and 0.50 (0.40–0.64) in women for nutrients, 0.43 (0.14–0.76) and 0.45 (0.06–0.74) respectively for food items, and 0.50 (0.30–0.70) and 0.57 (0.39–0.66) respectively for food groups. Relatively higher agreement percentages for intakes of nutrients and food groups with high validity were obtained together with lower complete disagreement percentages.
Conclusions: The FFQ has a high reproducibility and a reasonably good validity, and is useful in assessing the usual intakes of nutrients, foods and food groups among a rural Japanese population.
(Received November 13 2001)
(Accepted August 20 2002)