The reliability of ten-year dietary recall: implications for cancer research.

Remote dietary intakes may be more important than recent diet in the etiology of cancer because of the long latency in cancer development. We examined the reliability of remote dietary recall over 10 y. Subjects were 56 adults participating in a cancer prevention trial in Western Australia. All subjects completed a 28-d diet record (DR) in 1991. A food-frequency questionnaire (FFQ) modified to ask respondents about their diet 10 y earlier was sent to each subject for completion in 2001. Remote intakes recalled from 10 y earlier using the FFQ were compared with the DR using the limits of agreement (LOA) method and Pearson correlation coefficients. Mean intakes of most nutrients did not differ between dietary methods. The LOA indicated that the FFQ could under- or overestimate DR estimates by >/=50%. For many nutrients, agreement between methods depended on the magnitude of intake. Pearson's correlation coefficients ranged from 0.02 for retinol to 0.66 for alcohol. These findings are similar to those of other studies that examined the reliability of recent and remote dietary intakes. They also show that using this FFQ, remote diet recalled from 10 y earlier may be as reliable as recent dietary recall.