There is an interesting new cycle helmet study published in the May\nissue of the journal Accident Analysis and Prevention. It is also\ncritical of the selection criteria used in the 2009 Cochrane review.\n\nsee\n\n[URL]http://dx.doi.org/10.1016/j.aap.2011.01.007[/URL]\n\nPublication bias and time-trend bias in meta-analysis of bicycle helmet\nefficacy: A re-analysis of Attewell, Glase and McFadden, 2001\nRune Elvik\nInstitute of Transport Economics, Gaustadalléen 21, NO-0349\nOslo, Norway\n\nAbstract\n\nThis paper shows that the meta-analysis of bicycle helmet efficacy\nreported by Attewell, Glase, and McFadden (Accident Analysis and\nPrevention 2001, 345–352) was influenced by publication bias and\ntime-trend bias that was not controlled for. As a result, the analysis\nreported inflated estimates of the effects of bicycle helmets. This\npaper presents a re-analysis of the study. The re-analysis included: (1)\ndetecting and adjusting for publication bias by means of the\ntrim-and-fill method; (2) ensuring the inclusion of all published\nstudies by means of continuity corrections of estimates of effect rely\non zero counts; (3) detecting and trying to account for a time-trend\nbias in estimates of the effects of bicycle helmets; (4) updating the\nstudy by including recently published studies evaluating the effects of\nbicycle helmets. The re-analysis shows smaller safety benefits\nassociated with the use of bicycle helmets than the original study.\n\n\nConclusions\n\nBased on the studies reviewed in this paper, the following\nconclusions can be drawn:\n\n1. A re-analysis has been performed of a meta-analysis of the protective\neffects of bicycle helmets reported in Accident Analysis and Prevention\n(Attewell et al., 2001 R.G. Attewell, K. Glase and M. McFadden, Bicycle\nhelmet efficacy: a meta-analysis, Accident Analysis and Prevention 33\n(2001), pp. 345–352. Article | PDF (100 K) | View Record in Scopus |\nCited By in Scopus (79)Attewell et al., 2001). The original analysis was\nfound to be influenced by publication bias and time-trend bias that were\nnot controlled for.\n\n2. When these sources of bias are controlled for, the protective effects\nattributed to bicycle helmets become smaller than originally estimated.\n\n3. When the analysis is updated by adding four new studies, the\nprotective effects attributed to bicycle helmets are further reduced.\nAccording to the new studies, no overall effect of bicycle helmets could\nbe found when injuries to head, face or neck are considered as a whole.\n\n4. The findings of this study are inconsistent with other meta-analyses,\nin particular a Cochrane review published in 2009. However, the study\ninclusion criteria applied in the Cochrane review are debatable.