"Motorcycle helmets protect motorcyclists who crash from sustaining head injury, and the results also suggest that motorcycle helmets protect motorcyclists who crash from death," study author Betty Liu, an epidemiologist at Oxford University in England, said in a statement.
Liu led an international group of researchers in updating a study conducted in 2004. After adding data from eight additional studies, the review of studies found helmet use reduced head injury risk by 69 percent and death by 42 percent.
The review, published in The Cochrane Library, said the findings are important to consider in those countries without mandatory motorcycle helmet laws, as well as in jurisdictions with weak or partial helmet legislation.
Fewer than half of U.S. states require every motorcycle rider -- drivers and passengers -- to wear a helmet; and four states have no helmet requirements whatsoever, said study co-author Dr. Rebecca Ivers, head of the Injury Prevention Program at the George Institute for International Health in Sydney.