Spouse-subject interviews and the reliability of diet studies

Recently published data suggest relationships between ingestion of a number of food items and risk of cancer of the stomach, bowel and mouth. This engenders concern over the accuracy of such data. To study this, dietary interviews of 158 males in the Western New York Study of Cancer Epidemiology are compared to their spouses' estimates of the husband's dietary histories as taken in separate interviews. Respondents were asked to estimate the frequency with which the males consumed each of several foods. For analysis, the frequency estimates were assembled into categories similar to those used in recent epidemiologic analysis: 5-7 times per week, 1-4 times per week, 1-3 times per month and less than once per month. Generally, 60-80% of respondents pairs agree exactly on the frequency of consumption for individual food items. Over 90% of spouse and respondent food frequency estimates are within one frequency category of each other. Radical disagreements between spouses are rare; generally, in less than 2% of spouse pairs does one member estimate the maximum frequency category, and the other minimum frequency category. The authors suggest therefore that, although diet histories are not precisely replicable, they must be adequate to reveal gross differences between cases and controls.