Validity and reproducibility of the food-frequency questionnaire used in the Shanghai Men's Health Study

We evaluated the validity and reproducibility of the FFQ used in the Shanghai Men's Health Study (SMHS). The study included 195 randomly selected participants of the SMHS who completed one FFQ at baseline, twelve 24-hour dietary recalls (24-HDR) (once a month for twelve consecutive months) and a second FFQ at the end of the study. The FFQ accounted for 88·78 % of the foods recorded in the 24-HDR surveys. The validity of the FFQ was evaluated by comparing nutrient and food group intake levels from the second FFQ and the multiple 24-HDR. Correlation coefficients ranged from 0·38 to 0·64 for macronutrients, 0·33 to 0·58 for micronutrients and 0·35 to 0·72 for food groups. Misclassification to opposite quartiles for nutrients and food groups was rare, ranging from 1·5 to 7·7 %, while exact agreement rates were between 31·8 and 53·3 %. The reliability of the FFQ was assessed by comparing the intake levels from the two FFQ. Correlation coefficients were 0·39 to 0·53 for macronutrients, 0·38 to 0·52 for micronutrients and 0·39 to 0·64 for food groups. Exact agreement rates for quartile distribution were between 31·8 and 49·2 %, while misclassification to opposite quartiles was between 1·5 and 6·2 %. These data indicate that the SMHS FFQ can reasonably categorise usual intake of nutrients and food groups among men living in urban Shanghai.