Participation Bias Assessment in Three High-Impact Journals

Studies into participation bias have examined participation trends,where it occurs, the factors affecting it, and methods to try to reduce it. However,some authors only discuss participation bias at the end of the study, some acknowledgeit and apply a method to try to reduce it, while others ignore it or dismiss it asnegligible. Issues of three high-impact epidemiology journals were examined; 81 articleswere read and reviewed for potential participation bias. Categories were used toclassify the approach taken to participation bias and the results recorded. Of the 81articles considered, 42 (51%) were eligible and could have suffered from participationbias. It was found that 57% of these articles ignored the effects of participation bias,while 17% only considered it briefly in the discussion. Few articles (22%) attempted toreduce the participation bias, with over half of these using unsuitable methods (55%).This review highlights how participation bias is often not considered and hence theconclusions drawn from these studies may not be correct