Analysis of recurrent events: a systematic review of randomised controlled trials of interventions to prevent falls

Rationale: there are several well-developed statistical methods for analysing recurrent events. Although there are guidelines for reporting the design and methodology of randomised controlled trials (RCTs), analysis guidelines do not exist to guide the analysis for RCTs with recurrent events. Application of statistical methods that do not account for recurrent events may provide erroneous results when used to test the efficacy of an intervention. It is unknown what proportion of RCTs of falls prevention studies have utilised statistical methods that incorporate recurrent events. Methods: we conducted a systematic review of RCTs of interventions to prevent falls in community-dwelling older persons. We searched Medline from 1994 to November 2006. We determined the proportion of studies that reported using three statistical methods appropriate for the analysis of recurrent events (negative binomial regression, Andersen-Gill extension of the Cox model and the WLW marginal model). Results: fewer than one-third of 83 papers that reported falls as an outcome utilised any appropriate statistical method (negative binomial regression, Andersen-Gill extension of the Cox model and Cox marginal model) to analyse recurrent events and fewer than 15% utilised graphical methods to represent falls data. Conclusion: RCTs that have a recurrent event end-point should include an analysis appropriate for recurrent event data such as negative binomial regression, Andersen-Gill extension of the Cox model and/or the WLW marginal model. We recommend that researchers and clinicians seek consultation with a statistician with expertise in recurrent event methodology.