High‐Dose Monthly Vitamin D for Prevention of Acute Respiratory Infection in Older Long‐Term Care Residents: A Randomized Clinical Trial

Objectives To determine the efficacy and safety of high‐dose vitamin D supplementation for prevention of acute respiratory infection ( ARI ) in older long‐term care residents. Design Randomized controlled trial investigating high‐dose vs standard‐dose vitamin D from 2010 to 2014. Setting Colorado long‐term care facilities. Participants Long‐term care residents aged 60 and older (n = 107). Intervention The high‐dose group received monthly supplement of vitamin D 3 100,000 IU , the standard‐dose group received a monthly placebo (for participants taking 400–1,000 IU /d as part of usual care) or a monthly supplement of 12,000 IU of vitamin D 3 (for participants taking <400 IU /d as part of usual care). Measurements The primary outcome was incidence of ARI during the 12‐month intervention. Secondary outcomes were falls and fractures, 25‐hydroxyvitamin D levels, hypercalcemia, and kidney stones. Results Participants (55 high dose, 52 standard dose) were randomized and included in the final analysis. The high‐dose group had 0.67 ARI s per person‐year and the standard‐dose group had 1.11 (incidence rate ratio ( IRR ) = 0.60, 95% confidence interval ( CI ) = 0.38–0.94, P = .02). Falls were more common in the high‐dose group (1.47 per person‐year vs 0.63 in standard‐dose group; IRR = 2.33, 95% CI = 1.49–3.63, P < .001). Fractures were uncommon and similar in both groups (high dose 0.10 vs standard dose 0.19 per person‐year; P = .31). Mean trough 25‐hydroxyvitamin D levels during the trial were 32. ng/ mL in the high‐dose group and 25.1 ng/ mL in the standard‐dose group. There was no hypercalcemia or kidney stones in either group. Conclusion Monthly high‐dose vitamin D 3 supplementation reduced the incidence of ARI in older long‐term care residents but was associated with a higher rate of falls without an increase in fractures.