Vitamin D with calcium supplementation and risk of atrial fibrillation in postmenopausal women

Abstract

Background: Atrial fibrillation (AF) is the most common arrhythmia in adults. Although vitamin D deficiency is associated with AF risk factors, retrospective studies of association with AF have shown mixed results. We sought to determine the efficacy of calcium and vitamin D (CaD) supplementation for AF prevention in a randomized trial.

Methods: We performed a secondary analysis of the Women's Health Initiative trial on CaD supplementation versus placebo. We linked participants to their Medicare claims to ascertain incident AF.

Results: Among 16,801 included participants, there were 1,453 (8.6%) cases of incident AF over an average of 4.5 years, at an average rate of 19.9 events per 1,000 person-years. We found no significant difference in incident AF rates between the CaD and placebo arms (hazard ratio 1.02 for CaD vs placebo, 95% CI 0.92-1.13). After multivariate adjustment, there was no significant association between baseline 25-hydroxyvitamin D serum levels and incident AF (hazard ratio 0.92 for lowest subgroup vs highest subgroup, 95% CI 0.66-1.28).

Conclusions: We present the first analysis of a large randomized trial of daily vitamin D supplementation for AF prevention. We found that CaD had no effect on incidence of AF in Women's Health Initiative CaD trial participants. We also found that baseline serum 25-hydroxyvitamin D level was not predictive of long-term incident AF risk.