Once-weekly dose of 8400 IU vitamin D₃ compared with placebo: Effects on neuromuscular function and tolerability in older adults with vitamin D insufficiency

Background: Vitamin D insufficiency, which is prevalent in older individuals, is associated with bone and muscle weakness and falls. Objective: We examined the effects of a weekly dose of 8400 IU vitamin D₃ on postural stability, muscle strength, and safety. Design: In this double-blind trial, subjects aged ≥70 y with serum 25-hydroxyvitamin D [25(OH)D] concentrations ≤20 but ≥6 ng/mL were randomly assigned to receive a weekly dose of 8400 IU vitamin D₃ (n = 114) or a placebo (n = 112). Mediolateral body sway with eyes open (assessed with the AccuSway^PLUS platform; Advanced Medical Technology Inc, Watertown, MA) was the primary endpoint. Secondary endpoints included the short physical performance battery (SPPB) and serum 25(OH)D concentrations. An analysis of covariance model was used for treatment comparisons. Safety and tolerability were monitored. Results: Serum 25(OH)D concentrations rose significantly (from 13.9 to 26.2 ng/mL, P <0.001) in patients treated with 8400 IU vitamin D₃ but not in patients treated with the placebo. After 16 wk, neither mediolateral sway nor SPPB differed significantly between treatment groups. However, in the post hoc analysis of patients subgrouped by baseline sway (≥0.46 compared with 3 significantly reduced sway compared with treatment with placebo (P = 0.047) in patients with elevated baseline sway but not in patients with normal baseline sway. Adverse experiences and incidences of hypercalcemia, hypercalciuria, and elevated creatinine were similar with both treatments. In patients treated with 8400 IU vitamin D₃, but not in placebotreated patients, parathyroid hormone decreased significantly. Conclusions: Weekly treatment with 8400 IU vitamin D₃ raised 25(OH)D concentrations in elderly, vitamin D-insufficient individuals. Treatment with 8400 IU vitamin D₃ did not reduce mediolateral sway significantly compared with treatment with placebo in this population, although in post hoc analysis, treatment with 8400 IU vitamin D ₃ reduced sway in the subgroup of patients who had elevated sway at baseline. Weekly treatment with 8400 IU vitamin D₃ was well tolerated. This trial was registered at clinicaltrials.gov as NCT00242476.