The effects of vitamin D supplementation on types of falls

Background/objectives: To assess whether vitamin D supplementation prevents specific fall subtypes and sequelae (e.g., fracture). Design: Secondary analyses of STURDY (Study to Understand Fall Reduction and Vitamin D in You)—a response-adaptive, randomized clinical trial. Setting: Two community-based research units. Participants: Six hundred and eighty-eight participants ≥70 years old with elevated fall risk and baseline serum 25-hydroxyvitamin D levels of 10–29 ng/ml. Intervention: 200 IU/day (control), 1000 IU/day, 2000 IU/day, or 4000 IU/day of vitamin D3. Measurements: Outcomes included repeat falls and falls that were consequential, were injurious, resulted in emergency care, resulted in fracture, and occurred either indoors or outdoors. Results: After adjustment for multiple comparisons, the risk of fall-related fracture was greater in the pooled higher doses (≥1000 IU/day) group compared with the control (hazard ratio [HR] = 2.66; 95% confidence interval [CI]:1.18–6.00). Although not statistically significant after multiple comparisons adjustment, time to first outdoor fall appeared to differ between the four dose groups (unadjusted p for overall difference = 0.013; adjusted p = 0.222), with risk of a first-time outdoor fall 39% lower in the 1000 IU/day group (HR = 0.61; 95% CI: 0.38–0.97; unadjusted p = 0.036; adjusted p = 0.222) and 40% lower in the 2000 IU/day group (HR = 0.60; 95%CI 0.38–0.97; p = 0.037; adjusted p = 0.222), each versus control. Conclusion: Vitamin D supplementation doses ≥1000 IU/day might have differential effects on fall risk based on fall location and fracture risk, with the most robust finding that vitamin D doses between 1000 and 4000 IU/day might increase the risk of first time falls with fractures. Replication is warranted, given the possibility of type 1 error.