The authors of a study that helped foment the public and governmental obsession with bike helmets later issued research that undermined their initial findings.
The 1989 study, by Frederick P. Rivara, Diane C. Thompson, and Robert S. Thompson, found that helmet usage reduced head injury by 85 percent, and the risk of brain injury by 89 percent.
Network blog Wash Cycle reports that other researchers were not able to replicate the results — a red flag. And a few years later the original researchers issued a report, recently reprinted, that basically repudiated their landmark study.
These numbers have been repeated ever since by a variety of medical and insurance organizations and government agencies, despite the fact that “later efforts to replicate those results found a weaker connection between helmets and head injuries.” In fact, in 2013, in response to a petition from WABA, the CDC and NHTSA agreed to remove these estimates from their website.
Thompson, Rivara and Thompson did another study in 1997 that shows no connection between helmet use and serious injury. In a review of questionnaires filled out by 3,390 cyclists injured over a three year period, they determined that “Risk for serious injury was not affected by helmet use (OR=0.9)…[and]…neck injury was not affected by helmet use.” Instead they determined that:
“Prevention of serious bicycle injuries cannot be accomplished through helmet use alone, and may require separation of cyclists from motor vehicles, and delaying cycling until children are developmentally ready.”