1 / 14

Correcting for measurement error in nutritional epidemiology

Correcting for measurement error in nutritional epidemiology. Ruth Keogh MRC Biostatistics Unit MRC Centre for Nutritional Epidemiology in Cancer Prevention and Survival IPH Showcase, 14 February 2011. What is the association between long term or usual dietary intake and disease risk?.

rob
Download Presentation

Correcting for measurement error in nutritional epidemiology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Correcting for measurement error in nutritional epidemiology Ruth Keogh MRC Biostatistics Unit MRC Centre for Nutritional Epidemiology in Cancer Prevention and Survival IPH Showcase, 14 February 2011

  2. What is the association between long term or usual dietary intake and disease risk? Measuring dietary intake • Food frequency questionnaires (FFQ) • Diet diaries/24 hour recalls • Biomarkers There is no gold standard measurement UK dietary cohort consortium • EPIC-Norfolk + 5 other cohorts • Case-control studies nested within cohorts • 4-7 day diaries, FFQs • Colorectal cancer, breast cancer, prostate cancer

  3. Food frequency questionnaires (FFQ)

  4. Diet diaries

  5. Diet diaries

  6. Choice of instrument FFQs • Designed to measure long term intake • Inexpensive  used for large populations • Subject to substantial measurement error Diet diaries • Measure actual intake • Very expensive to process • More highly correlated with objective biomarkers of intake • Still subject to error UK dietary cohort consortium • One of only a small number of studies using diaries/24 hr recalls as the main instrument • Interested in correcting for error in dietary diary measurements

  7. Effects of measurement error • Biased associations – usually attenuated • Loss of power to detect associations • Can hide nonlinear association shapes

  8. Effects of measurement error • Biased associations – usually attenuated • Loss of power to detect associations • Can hide nonlinear association shapes

  9. Effects of measurement error • Biased associations – usually attenuated • Loss of power to detect associations • Can hide nonlinear association shapes

  10. Correcting for measurement error True diet-disease association Estimating  when we can’t observe Ti Linear regression calibration model

  11. Fitting the model We need to understand the structure of the error in diet diary measurements Ri Random error in diary measurements: Suppose we have another diary measurement for some people In fact we can show that

  12. Fibre intake and colorectal cancer Dahm CC, Keogh RH et al. Dietary Fiber and Colorectal Cancer Risk: A Nested Case–Control Study Using Food Diaries. JNCI 2010

  13. However… We do not believe that diet diaries are subject only to random error Biomarker studies suggest • error in diaries depends on true intake • errors in replicate diaries are not independent We cannot estimate the extra parameters using repeat measurements • to correct for error we need unbiased measurements, e.g. biomarker • biomarkers not available for most nutrients Different assumptions about the type of error in Ri can give very different corrected estimates

  14. Challenges • Measurement error can have severe effects on observed diet-disease associations • What we assume about the form of the error can have strong effects on ‘corrected’ estimated associations • Biomarkers can help us to understand the structure of the measurement error Also… • We often want to adjust for other dietary variables, such as total energy intake • All dietary variables in the model are measured with error…

More Related