Differences in overlapping meta-analyses of vitamin D supplements and falls
Abstract
CONTEXT: Overlapping meta-analyses on the same topic are common and often report discordant results. An Endocrine Society (ES) meta-analysis reported that vitamin D with calcium reduced the risk of falls, whereas vitamin D monotherapy had no effect. Despite meta-analyzing an overlapping set of trials, we concluded that vitamin D with or without calcium had no effect on falls.
OBJECTIVE: The objective of the study was to determine the reasons for the different conclusions from the two meta-analyses.
METHODS: We extracted raw data from the 25 randomized controlled trials included in the ES meta-analysis, calculated the treatment effect for each trial, compared them with the published ES meta-analysis, and determined the reason for any differences.
RESULTS: Of the 25 trials, there were differences in 14 results (56%) between the two meta-analyses. In the ES meta-analysis, data were used from a subset of falls or participants (four trials), from trial completers (three trials), or were imputed from fracture data (one trial). Other differences resulted from use of adjusted results from original papers (two trials), differences in incorporating data from multiarm and factorial studies (three trials), and inconsistent group numbers reported in original papers (two trials). In a reanalysis of the ES meta-analysis using unadjusted analyses and all randomized participants, there was a marginal effect of vitamin D with or without calcium on falls [relative risk (RR) 0.95, 95%…
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Evidence Hub reads this as a meta-analysis, done in people. Its evidence level is 1 of 5 (Highest · pooled evidence). Pooled evidence from several studies sits at the top of the evidence pyramid.
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