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Full-Text Articles in Physical Sciences and Mathematics
A Comparison Of Techniques For Handling Missing Data In Longitudinal Studies, Alexander R. Bogdan
A Comparison Of Techniques For Handling Missing Data In Longitudinal Studies, Alexander R. Bogdan
Masters Theses
Missing data are a common problem in virtually all epidemiological research, especially when conducting longitudinal studies. In these settings, clinicians may collect biological samples to analyze changes in biomarkers, which often do not conform to parametric distributions and may be censored due to limits of detection. Using complete data from the BioCycle Study (2005-2007), which followed 259 premenopausal women over two menstrual cycles, we compared four techniques for handling missing biomarker data with non-Normal distributions. We imposed increasing degrees of missing data on two non-Normally distributed biomarkers under conditions of missing completely at random, missing at random, and missing not …
Sleep Patterns, Urinary Levels Of Melatonin And Subsequent Weight Change In The Women’S Health Initiative Observational Study, Nicole M. Barron
Sleep Patterns, Urinary Levels Of Melatonin And Subsequent Weight Change In The Women’S Health Initiative Observational Study, Nicole M. Barron
Masters Theses
Results from prospective studies examining associations between sleep duration and weight gain have been mixed. Melatonin has been hypothesized to mediate the association between sleep duration and weight/body composition. In cross-sectional studies, aMT6s has been shown to be inversely associated with weight/body fat percentage. We examined associations between baseline sleep duration, insomnia status, aMT6s levels with weight/body fat percentage through 6 years, utilizing a subset 690 women who participated in a breast cancer case-control study nested within the WHI-OS. Multi-variable and mixed-effects regression was used to calculate beta-coefficients and 95% confidence intervals. Cross-sectional analyses showed urinary aMT6s levels were inversely …