Parathormone, vitamin D and the risk of atrial fibrillation in older adults: a prospective study

Background & aims: Vitamin D and parathormone (PTH) have been associated with cardiovascular outcomes, but their impact on atrial fibrillation (AF) onset is still unclear. We explored the influence of serum 25-hydroxyvitamin D (25[OH]D) and PTH on AF risk in older adults. Methods and results: Data come from 2418 participants enrolled in the Progetto Veneto Anziani study. Serum 25(OH)D and intact PTH were measured using radioimmunoassay and two-site immunoassay, respectively. The associations between 25(OH)D, PTH and adjudicated AF cases over 4-years were explored by Cox regression. Over the follow-up, 134 incident cases of AF were assessed. The incidence rate of the sample was 13.5 (95%CI 11.4-15.9) per 1000 person-years, and was higher among those with high PTH levels (high: 16.4 [95%CI 11.3-24.0] per 1000 person-years), especially when associated to low 25(OH)D (20.3 [95%CI 12.9-32.3] per 1000 person-years). At Cox regression, only high PTH was significantly associated to an increased risk of AF (HR = 1.90, 95%CI 1.27-2.84). A marginal significant interaction (p = 0.06) was found between 25[OH]D and PTH concentrations in influencing AF risk. When exploring the risk of AF for combined categories of 25(OH)D and PTH, we found that those with high PTH and low 25(OH)D levels had an AF risk twice as high as that of people with normal values (HR = 2.09, 95%CI 1.28-3.42). Conclusion: The risk of AF may be increased by high PTH levels, especially when associated with 25(OH)D deficiency. The identification and treatment of high PTH or vitamin D deficiency may thus contribute to lower the risk of AF.