Importance Vitamin D deficiency has been associated with poor physical performance.
Objective To determine the effectiveness of high-dose vitamin D in lowering the risk of functional decline.
Design, Setting, and Participants One-year, double-blind, randomized clinical trial conducted in Zurich, Switzerland. The screening phase was December 1, 2009, to May 31, 2010, and the last study visit was in May 2011. The dates of our analysis were June 15, 2012, to October 10, 2015. Participants were 200 community-dwelling men and women 70 years and older with a prior fall.
Interventions Three study groups with monthly treatments, including a low-dose control group receiving 24 000 IU of vitamin D3 (24 000 IU group), a group receiving 60 000 IU of vitamin D3 (60 000 IU group), and a group receiving 24 000 IU of vitamin D3 plus 300 μg of calcifediol (24 000 IU plus calcifediol group).
Main Outcomes and Measures The primary end point was improving lower extremity function (on the Short Physical Performance Battery) and achieving 25-hydroxyvitamin D levels of at least 30 ng/mL at 6 and 12 months. A secondary end point was monthly reported falls. Analyses were adjusted for age, sex, and body mass index.
Results The study cohort comprised 200 participants (men and women ≥70 years with a prior fall). Their mean age was 78 years, 67.0% (134 of 200) were female, and 58.0% (116 of 200) were vitamin D deficient (<20 ng/mL) at baseline. Intent-to-treat analyses showed that, while 60 000 IU and 24 000 IU plus calcifediol were more likely than 24 000 IU to result in 25-hydroxyvitamin D levels of at least 30 ng/mL (P = .001), they were not more effective in improving lower extremity function, which did not differ among the treatment groups (P = .26). However, over the 12-month follow-up, the incidence of falls differed significantly among the treatment groups, with higher incidences in the 60 000 IU group (66.9%; 95% CI, 54.4% to 77.5%) and the 24 000 IU plus calcifediol group (66.1%; 95% CI, 53.5%-76.8%) group compared with the 24 000 IU group (47.9%; 95% CI, 35.8%-60.3%) (P = .048). Consistent with the incidence of falls, the mean number of falls differed marginally by treatment group. The 60 000 IU group (mean, 1.47) and the 24 000 IU plus calcifediol group (mean, 1.24) had higher mean numbers of falls compared with the 24 000 IU group (mean, 0.94) (P = .09).
Conclusions and Relevance Although higher monthly doses of vitamin D were effective in reaching a threshold of at least 30 ng/mL of 25-hydroxyvitamin D, they had no benefit on lower extremity function and were associated with increased risk of falls compared with 24 000 IU.
