Assessment of participation bias in cohort studies: systematic review and meta-regression analysis

Abstract The proportion of non-participation in cohort studies, if associated with both the exposure and the probability of occurrence of the event, can introduce bias in the estimates of interest. The aim of this study is to evaluate the impact of participation and its characteristics in longitudinal studies. A systematic review (MEDLINE, Scopus and Web of Science) for articles describing the proportion of participation in the baseline of cohort studies was performed. Among the 2,964 initially identified, 50 were selected. The average proportion of participation was 64.7%. Using a meta-regression model with mixed effects, only age, year of baseline contact and study region (borderline) were associated with participation. Considering the decrease in participation in recent years, and the cost of cohort studies, it is essential to gather information to assess the potential for non-participation, before committing resources. Finally, journals should require the presentation of this information in the papers.

摘要 若队列研究（cohort studies）的不参与比例同时与暴露因素及事件发生概率相关，则会对目标估计值引入偏倚。本研究旨在评估纵向研究（longitudinal studies）中参与情况及其特征所产生的影响。本研究针对描述队列研究基线（baseline）参与比例的相关文献，在MEDLINE、Scopus及Web of Science数据库中开展了系统综述（systematic review）。在初步检索得到的2964篇文献中，最终纳入50篇。平均参与率为64.7%。采用混合效应元回归模型（meta-regression model with mixed effects）进行分析后发现，仅年龄、基线接触年份及研究地区（关联程度临界显著）与参与情况存在关联。鉴于近年来参与率持续下滑，且队列研究的开展成本不菲，在投入研究资源前，有必要收集相关信息以评估不参与情况带来的潜在偏倚风险。最后，学术期刊应要求论文中呈现该类相关信息。