Subgroup analyses showed that these results were generally consistent regardless of the calcium or vitamin D dose , sex , fracture history , dietary calcium intake , and baseline serum 25-hydroxyvitamin D concentration .
Conclusions and Relevance In this meta- analysis of r and omized clinical trials , the use of supplements that included calcium , vitamin D , or both compared with placebo or no treatment was not associated with a lower risk of fractures  among community-dwelling older adults .
Importance The increased social and economic burdens for osteoporosis-related fractures worldwide make the prevention of such injuries a major public health goal .
Previous studies have reached mixed conclusions regarding the association between calcium , vitamin D , or combined calcium and vitamin D supplements and fracture incidence in older adults .
Objective To investigate whether calcium , vitamin D , or combined calcium and vitamin D supplements are associated with a lower fracture incidence in community-dwelling older adults .
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
Subgroup analyses showed that these results were generally consistent regardless of the calcium or vitamin D dose , sex , fracture history , dietary calcium intake , and baseline serum 25-hydroxyvitamin D concentration .
Conclusions and Relevance In this meta- analysis of r and omized clinical trials , the use of supplements that included calcium , vitamin D , or both compared with placebo or no treatment was not associated with a lower risk of fractures  among community-dwelling older adults .
Importance The increased social and economic burdens for osteoporosis-related fractures worldwide make the prevention of such injuries a major public health goal .
Previous studies have reached mixed conclusions regarding the association between calcium , vitamin D , or combined calcium and vitamin D supplements and fracture incidence in older adults .
Objective To investigate whether calcium , vitamin D , or combined calcium and vitamin D supplements are associated with a lower fracture incidence in community-dwelling older adults .