A Case-Control Study of the Effectiveness of Bicycle Safety Helmets

TLDR

Bicycling accidents cause many serious injuries and about 1300 deaths per year in the U.S., mainly from head injuries, yet convincing evidence of helmet effectiveness is lacking. We conducted a one‑year case‑control study with 235 head‑injury cases and two control groups (433 ER patients with non‑head injuries and 558 HMO members with prior bicycle accidents). Helmet use was associated with an 85 % reduction in head‑injury risk (OR 0.15) and an 88 % reduction in brain‑injury risk (OR 0.12), with only 7 % of head‑injury cases wearing helmets versus 24 % of ER controls and 23 % of HMO controls. (N Engl J Med 1989;320:1361–7.).

Abstract

Bicycling accidents cause many serious injuries and, in the United States, about 1300 deaths per year, mainly from head injuries. Safety helmets are widely recommended for cyclists, but convincing evidence of their effectiveness is lacking. Over one year we conducted a case-control study in which the case patients were 235 persons with head injuries received while bicycling, who sought emergency care at one of five hospitals. One control group consisted of 433 persons who received emergency care at the same hospitals for bicycling injuries not involving the head. A second control group consisted of 558 members of a large health maintenance organization who had had bicycling accidents during the previous year. Seven percent of the case patients were wearing helmets at the time of their head injuries, as compared with 24 percent of the emergency room controls and 23 percent of the second control group. Of the 99 cyclists with serious brain injury only 4 percent wore helmets. In regression analyses to control for age, sex, income, education, cycling experience, and the severity of the accident, we found that riders with helmets had an 85 percent reduction in their risk of head injury (odds ratio, 0.15; 95 percent confidence interval, 0.07 to 0.29) and an 88 percent reduction in their risk of brain injury (odds ratio, 0.12; 95 percent confidence interval, 0.04 to 0.40). We conclude that bicycle safety helmets are highly effective in preventing head injury. Helmets are particularly important for children, since they suffer the majority of serious head injuries from bicycling accidents. (N Engl J Med 1989;320:1361–7.)