It seems intuitive helmets are beneficial – helmet vs. pavement or brain vs. pavement – yet the topic is somehow controversial. The only question should not be “if”, but the magnitude of the protective effect.
This brief article is a simple survey of motorcycle and moped accidents in Hawaii, stratified by helmet use or non-use. There are only small differences in admission to hospital and mortality in the overall cohort, however, those differences are magnified when further broken out into motorcycle or moped use. The key data: 3.5% fatality rate in helmeted motorcycle crashes versus 8.7% fatality rate in unhelmeted. The corresponding data for mopeds was 0.7% versus 1.1%. The authors performed multivariate logistic regression to adjust for age, crash location, and gender with no substantial effect on overall results.
This is retrospective, billing database data, and there are biases and missing information associated with limiting the reporting of only patients for whom EMS was contacted. This data also does not mention the cause of death – which would make for a much stronger association between fatality and helmet use if head injuries were implicated in the difference.
Regardless, most of the contextual evidence leans towards a protective effect for helmets, and the effect appears magnified as speed increases. If surviving a motorcycle accident is preferable to the alternative, it seems helmets are the way to go.
“Helmet use among motorcycle and moped riders injured in Hawaii: Final medical dispositions from a linked database”
http://www.ncbi.nlm.nih.gov/pubmed/25494427