Hip fracture risk in relation to vitamin D : quantifying the different types of evidence
Abstract
Background: Hip fractures cause significant morbidity and mortality and are often associated with bone demineralisation. Vitamin D plays an essential role in bone mineralisation. The evidence of a benefit of vitamin D supplementation for the prevention of hip fractures is apparently conflicting. While observational studies generally show a strong association between low vitamin D status (usually measured as the serum concentration of 25-hydroxyvitamin D, 25(OH)D) and increased risk of hip fractures, evidence from randomised controlled trials (RCTs) is less consistent. Despite this, widespread and costly vitamin D testing and supplementation continues. Objective: To assess quantitatively the evidence on vitamin D and hip fracture and investigate the implications of key limitations in current studies, in particular, variability in serum 25(OH)D measurement and confounding, for the interpretation of observational studies. Method and Results: Five published studies are presented. First, a systematic review and meta-analysis of current evidence showed an overall null effect of RCTs of vitamin D supplementation vs placebo/control (RR=1.13[95%CI 0.98-1.29]), both at high and low dose, on the risk of hip fracture. In apparent contrast, meta-analysis of seventeen case-control studies showed significantly lower serum 25(OH)D levels in hip fracture cases versus controls, with greater differences in 25(OH)D levels in studies with population- compared with hospital-based controls. The…
How strong is the evidence?
Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 813 participants or records.
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