http://worldtransportjournal.com/wp-con ... eb-opt.pdf
It is a long paper that shows major weaknesses in the meta analysis report.
Cycle helmets are a contentious issue which stems from evidence both for and
against their use and the negative effects from when legislation is imposed, which
has led to fines for non-wearers, some people cycling less or stopping and health
implications. A meta-analysis by Olivier and Creighton includes reports that compare
the proportion of head injuries or other injuries for wearer vs non-wearers.
Weaknesses in this approach stem from the combined effect of issues which affect
both the accident rate and head injury rate for helmeted vs non-helmeted or not
fully being able to evaluate the differences that occur. The meta-analysis claims that
helmet use is associated with odds reductions of 51% for head injury, 69% for serious head injury,
33% for face injury and 65% for fatal head injury. When examined in detail, all were found to be
unreliable claims due to weaknesses of the supporting evidence and methodology.