Atrial fibrillation (AF), a common heart rhythm disorder, poses significant health risks, particularly in older adults. Recent studies have suggested an association between vitamin D deficiency and an increased risk of AF. However, limited research has investigated the impact of vitamin D supplementation on AF incidence in healthy individuals. In a post hoc analysis of a randomized trial conducted in Finland, researchers explored the potential benefits of high-dose vitamin D supplementation in preventing AF.

The study involved 2495 vitamin D-sufficient, healthy older adults, with an average age of 68.2 years, 43% of whom were women. Participants were randomly assigned to one of three groups: a placebo group or two intervention groups receiving either 1600 IU/day or 3200 IU/day of vitamin D3. Serum 25(OH)D3 concentrations were measured, and data on incident AF were collected from national health records.

Key Findings:

Among the study participants, 190 individuals were diagnosed with AF. Over an average follow-up period of 4.1 years, the risk of incident AF was reduced by 27% in the group receiving 1600 IU/day of vitamin D3 compared to the placebo group (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.52 – 1.02; P = .07). The group receiving 3200 IU/day of vitamin D3 showed a 32% reduction in incident AF risk (HR, 0.68; 95% CI, 0.48 – 0.96; P = .03). When combining the results of both vitamin D groups, the risk of incident AF was reduced by 30% compared to the placebo group (HR, 0.70; 95% CI, 0.53 – 0.94; P = .02).

Upon excluding participants on antiarrhythmic medications at baseline, the 1600 IU/day group exhibited a significant 27% reduction in AF risk (95% CI, 4% – 58%; P = .03), while the 3200 IU/day group showed a nonsignificant 30% reduction (95% CI, 5% – 53%; P = .08).

Implications for Practice:

The authors suggest that high-dose vitamin D3 supplementation could potentially reduce the incidence of AF in generally healthy and largely vitamin D-sufficient elderly populations. However, the study emphasizes the need for additional controlled trials, particularly in diverse populations, to validate these findings and establish the optimal dosage and duration of vitamin D supplementation.

Study Details and Limitations:

The study was conducted by Jyrki K. Virtanen, PhD, and colleagues from the University of Eastern Finland and published in the American Heart Journal. It is important to note that AF was not a primary outcome in the study and the results differ from those of other randomized controlled trials. Additionally, specific details regarding the type of AF and participants’ history of AF were not available. Furthermore, the study population comprised solely White individuals from Finland, potentially limiting the generalizability of the results.

Disclosures:

The study received support from various foundations and organizations, including the Academy of Finland and the Finnish Cultural Foundation. Coauthors disclosed relevant financial relationships, including grants from the National Institutes of Health and Mars Edge, and a grant from Orion Corp.

Conclusion:

The post hoc analysis of a randomized trial conducted in Finland indicates that high-dose vitamin D supplementation may play a role in preventing atrial fibrillation in healthy elderly men and women. These findings highlight the potential importance of maintaining optimal vitamin D levels in reducing the risk of AF. However, further research is needed to validate these results and establish the broader applicability of vitamin D supplementation in diverse populations.