Clinical question Is an annual high dose of vitamin D (500,000 IU) effective in preventing falls and fractures in women 70 years or older who are at high risk of fracture?

Bottom line A once-a-year high dose of vitamin D (500,000 IU) actually increases the risk of falls and hip fractures in elderly women at high risk of osteoporotic fracture. Other studies of oral or intramuscular vitamin D using dose schedules other than once a year have shown a benefit in reducing fracture risk. The authors speculate that high serum levels of vitamin D or metabolites from a large once-a-year dose may be harmful. (Level of evidence = 1b)

Synopsis Daily supplementation of vitamin D (800 IU) has been shown to reduce the risk of hip fractures in elderly women and men. Because many patients have difficulty remembering to take regular daily medication, these investigators wished to determine whether a single annual high dose of vitamin D would be similarly beneficial. Eligible participants included women, 70 years or older, at high risk of osteoporotic hip fracture, defined by maternal hip fracture, past fracture, or recent self-reported falling episodes. Exclusion criteria included current regular use of at least 400 IU vitamin D daily, or other antifracture therapy. Study participants (N = 2,258) randomly received (concealed allocation assignment) a single dose of vitamin D 500,000 IU or matched placebo once a year in the autumn or winter for 3 to 5 years. The groups were similar with respect to daily calcium intake (median = 976 mg daily). Complete follow-up for all participants occurred for 12 months after their last dose of study medication. Individuals assessing outcomes remained masked to treatment group assignment. Using intention-to-treat analysis, women in the vitamin D group had significantly more fractures than women in the placebo group (171 vs 135; number needed to treat to harm = 32; 95% CI, 17-343). Women in the vitamin D group also fell significantly more often than those who took placebo.

Sanders KM, Stuart AL, Williamson EJ, et al. Annual high-dose oral vitamin D and falls and fractures in older women: a randomized controlled trial. JAMA. 2010;303(18):1815-1822.

 
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