Risk factors for reporting adverse events and for study withdrawal in a population-based trial of vitamin D supplementation

Publication date: Available online 18 November 2019Source: The Journal of Steroid Biochemistry and Molecular BiologyAuthor(s): Z Malihi, Z Wu, CMM Lawes, J Sluyter, D Waayer, L Toop, K-T Khaw, CA Camargo, R ScraggABSTRACTWith increasing numbers of randomized controlled trials (RCTs) investigating potential health events of vitamin D supplementation, a better understanding is required of the risk factors for adverse events and for study withdrawals. This analysis aimed to identify baseline risk factors of reporting an adverse event in a multi-year randomized double-blinded placebo-controlled trial of vitamin D supplementation. The secondary aim was to investigate if adverse events were associated with study withdrawals. We analyzed data from the Vitamin D Assessment (ViDA) study: 5,110 adults, aged 50-84 years, living in Auckland, New Zealand. Monthly doses of 100,000 IU vitamin D3 or placebo were mailed to participants homes, with a questionnaire to collect data on adverse events and adherence to the study capsule (initially monthly, then 4-monthly). Median follow-up was 3.3 years. Data were analysed using multivariable log-binomial regression and Cox-regression. During the follow-up period, 818 people reported adverse events and 412 withdrew or stopped returning questionnaires. Vitamin D was not associated with reporting of adverse events. Of sociodemographic factors, ethnicity was associated with reporting adverse events: compared to European participants, Maori and Pacific...
Source: The Journal of Steroid Biochemistry and Molecular Biology - Category: Biochemistry Source Type: research