Comparison of diet history interview and self completed questionnaire in assessment of diet in an elderly population

The aim of the study was to determine the reliability of a diet history interview with a short self completed questionnaire of a basic design used in other studies in the United Kingdom.

The study used a cohort of elderly people randomly divided into two groups after stratification for sex. Members of one group completed the questionnaire first and were interviewed later; the procedure was reversed for the other group.

Participants were drawn from registers of two general practitioners at a Nottingham health centre.

All non-Asian men aged 65-74 years and women aged 59-65 years registered with the practices were identified (n = 152); 20 could not be traced and two were too ill, leaving 130 possible participants. Of these, 80 took part in the study.

Ranking of subjects in terms of estimated fat, fibre, and calcium intakes was compared in the history interview and in the self completed questionnaire. Agreement in tertile ranking was 58% for fibre, 53% for fat, and 49% for calcium. Corresponding correlation coefficients for estimated nutrient intakes were 0.49, 0.45, and 0.41 respectively. The differences in nutrient intakes estimated by the two methods were not affected by age, sex, marital status, or smoking patterns. Subjects in the group asked to complete the questionnaire before being interviewed showed greater percentage concordance for tertile ranking, but this reached significance only for fat intake.

The two methods provide estimates of intakes similar to those found in other studies in the United Kingdom, and the agreement between them in terms of tertile ranking is also similar to previous studies. The incidence of gross misclassification was low.