Assessing lifetime diet: reproducibility of a self-administered, non-quantitative FFQ

Objective To demonstrate test-retest reliability (reproducibility) of a new self-administered lifetime diet questionnaire, with a focus on foods relevant to cognitive health in older age.Design The reproducibility of dietary recall over four or five life periods was assessed by administering the questionnaire at two time points to an older cohort. The period between questionnaire administrations was 7 weeks. Polychoric correlations measured the association between recall at time 1 and time 2 and the weighted statistic measured the level of recall agreement for food groups across the two administrations of the questionnaire.Setting Adelaide, South Australia.Subjects Fifty-two cognitively healthy, older-age, community-dwelling adults completed the Lifetime Diet Questionnaire; mean age 818 (sd 44) years, range 70-90 years.Results The questionnaire showed very good reproducibility in this sample with a mean polychoric correlation coefficient of 081 between administration at time 1 and time 2, and an average weighted of 049 for the level of recall agreement between food groups.Conclusions The demonstrated reliability of this lifetime diet questionnaire makes it a useful tool to assess potential relationships between long-term dietary intake and later-age cognitive outcomes.