DIFFERENCES IN REPORTED FOOD FREQUENCY BY SEASON OF QUESTIONNAIRE ADMINISTRATION - THE 1987 NATIONAL-HEALTH INTERVIEW SURVEY

We assessed seasonal reporting bias in a 59-item food frequency questi onnaire (FFQ) administered throughout 1 year using data from the 1987 National Health Interview Survey (N = 20,143 adults). Few meaningful d ifferences were found in the proportion of individuals reporting rarel y or-never consuming a: food by season of questionnaire administration . Seasonal reporting bias is evident in FFQs, however, and appears to be due to reporting most recent consumption Using gender-specific medi an servings per week, an analysis using logistic regression showed tha t the estimated proportion of individuals reporting food intake at gre ater than the yearly: median differed:between any two seasons by at le ast 5% of the population for 22 foods. We compared gender-specific qui ntiles of selected nutrients/food groups for the whole year and each s eason; these showed that quintile assignment never varied by mere than one adjacent quintile. The most frequent shift in quintile assignment , involving as many as 18.5 % of women in the summer, occurred for cit rus fruits. The intake biases are small and do not greatly affect popu lation estimates if the FFQ is administered in all seasons, but they m ay somewhat affect classification of individuals into quantiles for so me foods/nutrients.