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Recall of remote diet

Recall of remote diet. Nutritional epidemiology WALTER WILLETT. Introduction. For some diseases, including many cancers,the effect of diet is hypothesized to occur many years before diagnosis—recall of remote diet---relative unstructured diet histories or food frequency questionnaire

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Recall of remote diet

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  1. Recall of remote diet Nutritional epidemiology WALTER WILLETT

  2. Introduction For some diseases, including many cancers,the effect of diet is hypothesized to occur many years before diagnosis—recall of remote diet---relative unstructured diet histories or food frequency questionnaire The validity of remotely recalled diet Published studies of recalled remote diet(Table 7-1)

  3. --BACK--

  4. Diet has some consistency over time • Recalled diet is heavily influenced by current diet • Actual past diet, recall of past diet, current diet(many studies,Figure 7-1) • These studies suggest that, if remote diet is of interest, focusing questions on the period of interest usually provides the most accurate information, although the use of current diet as a surrogate for past diet provides similar information in some instances.

  5. --BACK--

  6. Factors associated with error in recall of diet over a period of 8 years(Kuzma and Lindsted, 1990): -diets changed over this period of time -with lower education and income -not associated with gender or age • Many other studies • To use current diet with adjustment for reported change in diet—not supportive

  7. Potential bias in case-control studies • The strong influence of current diet on recall---possible bias when diet has changed after the etiologically relevant period of exposure. • Diets of cases, but not controls, may have changed as a result of the diagnosis or the impact of progressive disease and its treatment. • The potential magnitude of recall bias due to the occurrence of disease : (studies)

  8. Recall bias was greatest for a greater time interval between the original and repeat dietary assessment and with more advanced cases of cancer. • In case control studies, cases will over- or underreport past dietary practices compared with controls. • Systematic bias Even if there is no systematic bias, differences in random error, that is, precision in reporting past diet, can distort the shape of dose-response relationships. Ex, greater random error for cases than controls would create a U-shaped relationship if there was no true overall relationship.

  9. Adventist Health Study (Lindsted and Kuzma,1990) cancer cases reported diets somewhat more precisely than did controls, which appeared to be due to greater changes in diets over time by controls.

  10. Summary • Studies of differential error in reporting of past diets by disease cases and controls indicates that bias findings can occur in some circumstances, but not in all studies. • The degree of illness of cases, the specific disease being studied, the specific dietary factors rather than just overall food intake-bias

  11. Summary • There are potential pitfalls in case-control studies of dietary factors. • Diet may be recalled with acceptable levels of missclassification up to approximately 10 years. • Educational level, disease status, and other factors may influence he error in reporting past diets.

  12. Summary • The degree of error—validation studies to evaluate factors that influence error and further methodologic evaluation and development is required to learn about the long – term health effects of childhood.

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