Cycle helmets are the subject of a great number of myths and exaggerations, some of which feature prominently in the promotion of helmets.
This claim originates from a single source – Thompson, Rivara and Thompson, 1989 – and has never even been approached by real-world evidence anywhere. The research on which the prediction was made has been widely criticised for fundamental methodological errors. The researchers themselves revised their prediction downwards to 69% for head injuries in 1996 (Thompson, Rivara and Thompson, 1996), but this too remains greatly in excess of real-world experience.
In places where helmet use has become significant, there has been no detectable reduction in head injuries relative to cycle use.
See: Why it is wrong to claim that cycle helmets prevent 85% of head injuries and 88% of brain injuries for a full explanation as to why this claim is wrong.
This prediction also comes from a single source (Dorsch, Woodward and Somers, 1987) and is not reflected by real-world experience. Fatality trends in countries where helmet use has become significant give no reason to believe that helmets have saved even a single life
In 1985 Dr Dorsch, an author of the source report, told an Australian parliamentary committee that the conclusions of the study should be treated with care. She said, "That was a hypothetical procedure based largely on an adult group of cyclists".
Many helmet wearers experience crash situations that lead them to believe that their helmet 'saved their life'. But across cyclists as a whole there is no evidence that helmets protect from death or serious injury. Such claims are perhaps an indication that helmeted cyclists are more likely to hit their heads if they crash and that they may be more likely to crash in the first place.
See: "A helmet saved my life" for a fuller discussion.
Dorsch MM, Woodward AJ, Somers RL, 1987. Do bicycle safety helmets reduce severity of head injury in real crashes?. Accident Analysis and Prevention 1987 Jun;19(3):183-90.
Thompson RS, Rivara FP, Thompson DC, 1989. A case control study of the effectiveness of bicycle safety helmets. New England Journal of Medicine 1989 v320 n21 p1361-7.
Thompson DC, Rivara FP, Thompson RS., 1996. Effectiveness of bicycle safety helmets in preventing head injuries: a case-control study. JAMA 1996 Dec 25;276(24):1968-73.