Vitamin D Supplementation Trials Aimed at Reducing Mortality Have Much Higher Power When Focusing on People with Low Serum 25-Hydroxyvitamin D Concentrations

Background: Evidence of an inverse association between serum vitamin D and mortality from epidemiological studies has prompted efforts to reduce mortality by vitamin D supplementation, either in targeted interventions for people with vitamin D insufficiency or deficiency, or in untargeted interventions regardless of baseline vitamin D status.Objective: We aimed to assess the expected impact of the 2 different approaches on effect sizes and power...