Vitamin D and vitamin D analogues for preventing fractures associated with involutional and post-menopausal osteoporosis.

BACKGROUND: Due to their known effects on bone metabolism, Vitamin D and related compounds have been proposed for the prevention of osteoporosis and fractures.

OBJECTIVES: To determine the effects of supplementation with Vitamin D or a Vitamin D analogue in the prevention of fractures of the axial and appendicular skeleton in elderly men or women with involutional or post-menopausal osteoporosis.

SEARCH STRATEGY: We searched MEDLINE, EMBASE, BIOSIS, CINAHL, HealthPLAN, Dissertation Abstracts, Index to UK Theses, Current Contents, and bibliographies of identified trials and reviews. Trials were also obtained from the Cochrane Musculoskeletal Injuries Group trials register. Date of the most recent search: December 1995.

SELECTION CRITERIA: Any randomised or quasi-randomised trial which compared Vitamin D or a Vitamin D analogue, either alone or in combination with calcium supplementation, with a placebo, no intervention, or the administration of calcium supplements, with fracture as an outcome, in elderly men or women with involutional or post-menopausal osteoporosis.

DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality, by use of a seven item scale, and extracted data. Additional information was sought from trialists. Where possible the data were pooled.

MAIN RESULTS: Fourteen trials recording 13 different comparisons were included. In the only trial of Vitamin D alone, protection against hip fracture was not confirmed. Two regimens, each represented by one large trial, which showed limited evidence of efficacy in reducing the incidence of hip or other appendicular skeleton fractures were: 1) Oral Vitamin D when accompanied by calcium supplementation. 2) 1,25 dihydroxy Vitamin D (calcitriol). This appeared more effective than calcium in a direct comparison. Regimens showing limited evidence of efficacy in reducing the incidence of vertebral deformity were: 1) 1,25 dihydroxy Vitamin D (calcitriol), which appeared more effective than calcium in one large trial, and more effective than placebo from pooled results of two small trials. 2) Oral 1-alpha hydroxy Vitamin D (alfacalcidol), when administered with calcium supplements (two small trials, which lacked power to confirm a possible effect). Hypercalcaemia and gastro-intestinal symptoms, reported in less than 5% of participants, were slightly more common when Vitamin D analogues were taken. However, the risk of death was marginally less.

REVIEWER'S CONCLUSIONS: Uncertainty remains about the efficacy of regimens which include Vitamin D or its analogues in fracture prevention. Particularly if co-supplementation of calcium is required, significant cost differences are likely to exist between regimens. Further randomised trials with economic evaluation are desirable before community fracture prevention programmes employing Vitamin D supplementation can be confidently introduced.