Vitamin D supplementation improves neuromuscular function in older people who fall.

BACKGROUND

vitamin D supplementation reduces the incidence of fractures in older adults. This may be partly mediated by effects of vitamin D on neuromuscular function.

OBJECTIVE

to determine the effects of vitamin D supplementation on aspects of neuromuscular function known to be risk factors for falls and fractures.

DESIGN

randomised, double-blind, placebo-controlled study.

SETTING

falls clinic taking referrals from general practitioners and accident and emergency department.

SUBJECTS

139 ambulatory subjects (>/=65 years) with a history of falls and 25-hydroxyvitamin D (25OHD) </=12 microg/l.

INTERVENTION

patients were randomised to receive a single intramuscular injection of 600,000 i.u. ergocalciferol or placebo.

OUTCOME MEASURES

assessments including biochemistry, postural sway, choice reaction time (CRT), aggregate functional performance time (AFPT), and quadriceps strength were carried out at baseline and 6 months post-intervention.

RESULTS

baseline characteristics were comparable between both groups. 25OHD in the treatment group increased significantly at 6 months. AFPT deteriorated in the control group and improved in the intervention group, representing a significant difference between groups (+6.6 s versus -2.0 s, t = 2.80, P < 0.05). Similar changes were observed for CRT (-0.06 s versus +0.41 s, t = -2.52, P < 0.01) and postural sway (+0.0025 versus -0.0138, t = 2.35, P < 0.02). There was no significant difference in muscle strength change between groups (-10 N versus -2 N, t = -1.26, ns). A significant correlation between change in AFPT and change in 25OHD levels was observed (r = 0.19, P = 0.03). There was no significant difference in the number of falls (0.39 versus 0.24, t = 1.08, P = 0.28) or fallers (14 versus 11, P = 0.52) between two groups.

CONCLUSIONS

vitamin D supplementation, in fallers with vitamin D insufficiency, has a significant beneficial effect on functional performance, reaction time and balance, but not muscle strength. This suggests that vitamin D supplementation improves neuromuscular or neuroprotective function, which may in part explain the mechanism whereby vitamin D reduces falls and fractures.