Publication bias and time‐trend bias in meta‐analysis of bicycle helmet efficacy: A re‐analysis of Attewell, Glase and McFadden, 2001

This paper shows that the meta‐analysis of bicycle helmet efficacy reported by Attewell, Glase, and McFadden (2001) was influenced by publication bias and time‐trend bias that was not controlled for. As a result, the analysis reported inflated estimates of the effects of bicycle helmets. This paper presents a re‐analysis of the study. The re‐analysis included: (1) detecting and adjusting for publication bias by means of the trim‐and‐fill method; (2) ensuring the inclusion of all published studies by means of continuity corrections of estimates of effect rely on zero counts; (3) detecting and trying to account for a time‐trend bias in estimates of the effects of bicycle helmets; (4) updating the study by including recently published studies evaluating the effects of bicycle helmets. The re‐analysis shows smaller safety benefits associated with the use of bicycle helmets than the original study.