Covariate Assessments (Modified): Information on lifestyle o…
Covariate Assessments (Modified): Information on lifestyle or dietary factors was obtained from the biannual questionnaires (i.e., 1986, 1988, 1990, 1992, and 1994) or food frequency questionnaires (FFQs; i.e., 1986, 1990, and 1994). To better approximate long-term nutrient intake, we calculated cumulatively updated intake using information from the 1986, 1990, and 1994 FFQs ( 19 ). Because plasma concentrations reflect recent intake, intakes of vitamin D… were calculated using the information from the FFQ closest to the time the blood sample was provided (1994 FFQ) or, if not available, from the most recent questionnaire administered before 1994 (96% of participants in the HPFS had provided information on dietary intake in 1994). Note: Suppose that in addition to the timing information provided above, the authors also noted that the FFQs asked participants to complete dietary assessments for the past 30 days. Food Frequency Questionnaires (FFQs) are detailed dietary assessments that capture the consumption of specific food items and portion sizes over the recall time period. They are used to determine nutrient intake for participants. Question 2e: Diet is considered to be a confounder of the relationship between sufficient vitamin D levels and colorectal cancer. Based on the information provided about dietary data collection for this study, describe the type(s) of bias that may impact study findings. How might this relate to the measurement of the exposure of interest? How might these biases impact study findings? Your answer should be 5-7 sentences.