Recontacting Participants in the Observing Protein and Energy Nutrition (OPEN) Study: Re-OPEN

NCI carries out extensive research and surveillance activities that rely on self-reported dietary information from questionnaires and interviews. Although scientists have long recognized that this information contains error, considerable uncertainty remains about its structure. The interpretation of findings from NCI's nutritional epidemiology and surveillance efforts is critically dependent on the assessment of dietary measurement error. We evaluated such measurement error in the previously conducted Observing Protein and Energy Nutrition Study (OPEN) conducted in 1999 and 2000. This study, the largest study of its kind, used unbiased biomarkers of dietary intake (doubly labeled water for energy and 24-hour urinary nitrogen for protein) to assess measurement error in dietary assessment methods commonly used in epidemiology and surveillance research around the world. The landmark findings indicate that relative risk estimates in nutritional epidemiology may be severely attenuated by the use of food frequency questionnaires and that the conventional use of 24-hour dietary recalls as reference measurements may lead to severe underestimates of the extent of this attenuation. Key questions remain regarding whether these findings hold in diverse populations, for other dietary-report or physical activity instruments, across varying nutrients and food groups, and how measurement error affects relative risks in existing prospective cohorts. In light of the OPEN study findings, we would like to re-contact participants, for whom we already have a wealth of nutritional biomarker data, in order to assess the structure of measurement error with respect to two other self-reported dietary assessment instruments: the food record and a food checklist-adjusted food frequency questionnaire. Our intent is to evaluate whether these instruments might have more favorable measurement error structure than the food frequency questionnaire, thereby providing better tools for nutritional epidemiology.