Effects of vitamin D supplementation on adherence to and persistence with long-term statin therapy: Secondary analysis from the randomized, double-blind, placebo-controlled ViDA study

Background and aims Long-term statin use increases survival. However, the adherence to and persistence with statin use are challenging and this influences the success of statin treatment. Our aim was to explore if monthly vitamin D supplementation (100,000-IU) improves the adherence to and persistence with long-term statin use in older adults. Methods We conducted a secondary analysis of a trial comparing data on dispensed statin prescriptions, between participants allocated to vitamin D supplementation or placebo, for those taking statin therapy. Primary outcomes were defined as adherence to (proportion of days covered by prescriptions ≥80%) and persistence (non-discontinuation of the statin therapy following an allowed 30 days gap between refills) with all statins over a 24-month measurement period of statin therapy. Secondary outcomes were defined as adherence and persistence at other measurement periods for all types of statins and for individual statins. Results Overall, 2494 participants were on long-term statins at follow-up (vitamin D = 1243, placebo = 1251). Compared with placebo, monthly vitamin D supplementation did not improve the proportion with adherence (risk ratio: 1.01, p=0.62), but improved the persistence probability of taking all statins after 24 months (hazard ratio: 1.15, p=0.02). In further analyses, significant differences were observed in the adherence to simvastatin, the first-line statin therapy. Conclusions Monthly vitamin D supplementation improved persistence with statins use over a 24-month measurement period in older adults on long-term statin therapy, especially for participants on simvastatin. The role of vitamin D supplementation as an adjunct therapy for patients on long-term statins merits further investigation.