Abstract
BACKGROUND: Attrition is a major obstacle for lifestyle interventions sustained for the medium-to-long term and can have significant consequences on the internal validity of a trial. When the degree of attrition differs between active and control arms this is termed differential attrition and is an important consideration during initial stages of trial planning. OBJECTIVES: The primary research question of this study was: what is the differential attrition between treatment arms in lifestyle interventions for prevalent chronic diseases? METHODS: We performed a systematic review and meta-analysis of 23 studies involving a lifestyle intervention component in cohorts with chronic diseases. The search accessed three databases: Scopus, Medline Ovid and Web of Science. Attrition between treatment arms was analysed using a random-effects model and examined the relationship between the relative attrition and potential moderators, such as time to final follow-up, time to first follow-up, type of disease, type of control, type of intervention and length of treatment. RESULTS: The pooled risk ratio was 1.00 (95% CI 0.97 - 1.03) and only one study fell outside this range. A univariable association was described between the pooled risk ration and length (years) to final follow-up, which did not remain in the multivariable model. CONCLUSIONS: Ultimately, we found no evidence of differential attrition in medium-to-long term lifestyle intervention studies for chronic disease, increasing confidence in conducting such studies with minimal potential of attrition bias. TRIAL REGISTRATION: PROSPERO registration number CRD42018084495 .