Boursiquot BC, et al. - Researchers investigated the efficacy of calcium and vitamin D (CaD) supplementation for atrial fibrillation (AF) prevention via performing a secondary analysis of the Women’s Health Initiative trial on CaD supplementation vs placebo. It was the first analysis of a large randomized trial of daily vitamin D supplementation for AF prevention. CaD was identified to have no effect on the incidence of AF. In addition, the investigators noted no predictive value of baseline serum 25-hydroxyvitamin D level for long-term incident AF risk.