For hip fracture , at a 15 % relative risk , the effect estimate lay between the futility boundary and the inferior boundary , meaning there is reliable evidence that vitamin D supplementation does not reduce hip fractures by this amount , but uncertainty remains as to whether it might increase hip fractures .
The effect estimate lay within the futility boundary at thresholds of 0·5 % for total hip , forearm , and total body bone mineral density , and 1·0 % for lumbar spine and femoral neck , providing reliable evidence that vitamin D does not alter these outcomes by these amounts .
INTERPRETATION Our findings suggest that vitamin D supplementation does not prevent fractures or falls , or have clinical ly meaningful effects on bone mineral density .
There were no differences between the effects of higher and lower doses of vitamin D. There is little justification to use vitamin D supplements to maintain or improve musculoskeletal health .
BACKGROUND The effects of vitamin D on fractures , falls , and bone mineral density are uncertain , particularly for high vitamin D doses .
We aim ed to determine the effect of vitamin D supplementation on fractures , falls , and bone density .
The effects of an open design on trial participant recruitment, compliance and retention – a randomized controlled trial comparison with a blinded, placebo-controlled design
Background In r and omized trials there may be no overriding reason whether or not to have a placebo control . Purpose We assessed the effects of an open trial design ( no placebo and people know what tablets they are given ) compared with a blinded , placebo-controlled design on recruitment , compliance and retention within a r and omized trial of secondary osteoporotic fracture prevention . Methods We undertook a r and omized controlled comparison nested within a placebo-controlled trial of nutritional supplementation amongst people aged 70 years or over who had previously sustained a fracture , recruited in a UK teaching hospital . R and omization was 2 : 1 in favour of the blinded , placebo-controlled trial design . Results From 180 eligible participants r and omized to receive information based on the open trial design , 134 ( 74.4 % ) consented to take part , compared with 233 ( 65.1 % ) of 358 people r and omized to the blinded , placebo-controlled design ( difference 9.4 % , 95 % confidence interval 1.3–17.4 % ) . Reluctance to take a placebo  and the desire to know tablet allocation were reasons given for not taking part in the blinded , placebo-controlled design . There was no significant difference in tablet compliance . Open trial participants were more likely to remain in the trial for one year ( difference 13.9 % , 95 % confidence interval 3.1–24.6 % ) , mainly reflecting the high retention of the open trial no tablet group compared to the open trial tablet group ( difference 23.6 % , 95 % confidence interval 11.9–35.2 % ) . The odds ratio for reporting an adverse event in the open trial compared to the blinded , placebo-controlled design was 0.64 ( 95 % confidence interval 0.28–1.49 ) , and for reporting a fracture was 0.81 ( 0.36–1.85 ) . Conclusions We conclude that using an open trial design may enhance participant recruitment and retention and thus improve generalizability and statistical power , but withdrawal rates may differ between the study allocations and may threaten the internal validity of the trial
For hip fracture , at a 15 % relative risk , the effect estimate lay between the futility boundary and the inferior boundary , meaning there is reliable evidence that vitamin D supplementation does not reduce hip fractures by this amount , but uncertainty remains as to whether it might increase hip fractures .
The effect estimate lay within the futility boundary at thresholds of 0·5 % for total hip , forearm , and total body bone mineral density , and 1·0 % for lumbar spine and femoral neck , providing reliable evidence that vitamin D does not alter these outcomes by these amounts .
INTERPRETATION Our findings suggest that vitamin D supplementation does not prevent fractures or falls , or have clinical ly meaningful effects on bone mineral density .
There were no differences between the effects of higher and lower doses of vitamin D. There is little justification to use vitamin D supplements to maintain or improve musculoskeletal health .
BACKGROUND The effects of vitamin D on fractures , falls , and bone mineral density are uncertain , particularly for high vitamin D doses .
We aim ed to determine the effect of vitamin D supplementation on fractures , falls , and bone density .