Objective: To design a Bayesian random effects model for pooling binary outcome data from cluster randomized trials (CRTs) with individually randomized trials (IRTs) and then use this model to determine if hip protectors decrease the risk of hip fracture in elderly nursing home residents.
Study design and setting: Eight electronic databases were searched; abstracts and papers were reviewed in duplicate. Randomized controlled trials of hip protectors in nursing homes were included. The pooled mean odds ratio (OR) of a hip fracture in an individual allocated to hip protectors with 95% credibility interval (CRI) was calculated.
Results: We included four trials of 1,922 individuals (including three CRTs). The pooled OR of an elderly nursing home resident sustaining one or more hip fractures with hip protector allocation was 0.40 (95% CRI 0.25, 0.61). The model was robust in multiple sensitivity analyses assuming alternative intracluster correlation coefficient values.
Conclusion: The Bayesian approach may be used in meta-analyses of IRTs and CRTs. Using this approach, we have determined that hip protectors decrease the risk of hip fracture in elderly nursing home residents. Methodologic limitations of the included trials and a possible herd effect in CRTs may have influenced these results.