The effect of recall bias on the association of calorie-providing nutrients and breast cancer.

This nested case-control study conducted within a large dietary cohort study examined whether recall bias could explain the inconsistent results obtained in case-control and cohort studies of the association between dietary fat and breast cancer. Cases were defined as women diagnosed with breast cancer between 1982 and 1987 who had completed a self-administered food frequency questionnaire on enrollment in the cohort study between 1982 and 1985. They were matched to two controls each, and the study subjects were asked in 1988 to complete a second diet questionnaire addressing their diets at the time of enrollment. The mean nutrient intakes for 325 cases who completed the first diet questionnaire six months or more before breast cancer diagnosis and their 628 matched controls were very similar for the prospectively and retrospectively collected diet questionnaires. There was little difference in the magnitude of the odds ratios estimated from the two questionnaires for the association between breast cancer risk and these nutrients. These data do not provide evidence for recall bias in retrospectively collected nutrient data from breast cancer cases compared with their matched controls.