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 D3 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 D3 (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 ARIs 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 D3 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.