Effects of Vitamin D Supplementation and 25-Hydroxyvitamin D Levels on the Risk of Atrial Fibrillation

The effects of vitamin D (Vit-D) deficiency and Vit-D treatment (VDT) on atrial fibrillation (AF) remain inconclusive. This study sought to determine the effects of VDT and nontreatment on AF risk in Vit-D-deficient patients without a previous history of AF. In this nested case-control study, 39,845 individuals with low 25-hydroxy-Vit-D ([25-OH]D) levels (<20 ng/ml) were divided into group-A (untreated, levels ≤20 ng/ml), group-B (treated, levels 21 to 29 ng/ml), and group-C (treated, levels ≥30 ng/ml). The risk of AF was compared utilizing propensity score-weighted Cox proportional hazard models. Among the individuals receiving VDT for ≥6 months, the risk of AF was significantly lower in group-B (hazard ratio [HR] 0.89, 95% confidence interval [CI] 0.80 to 0.98, p = 0.03] and group-C (HR 0.84, 95% CI 0.73 to 0.0.95, p = 0.007] than in group-A. A subgroup analysis of men >65 years showed individuals with hypertension had a significantly lower risk of AF in group-C than in group-B (HR 0.79, CI 0.65 to 0.94, p = 0.02) and group-A (HR 0.78, CI 0.64 to 0.96, p = 0.012). A similar result was found in men >65 years with diabetes mellitus in group-C compared with group-B (HR 0.69, CI 0.51 to 0.93, p = 0.012) and group-A (HR 0.63, CI 0.47 to 0.84, p = 0.002). In what is, to best of our knowledge, the largest observational study to date of patients with Vit-D deficiency and no previous history of AF, (25-OH)D level of >20 ng/ml with VDT for ≥6 months was associated with a significantly lower risk of AF. Additionally, men >65 years with hypertension or diabetes mellitus had a further decrease in AF risk when the (25-OH)D levels were ≥30 ng/ml.