Use of alcohol as a risk factor for bicycling injury

CONTEXT: Bicycling is one of the leading causes of recreational injuries. Elevated blood alcohol concentrations (BACs) are found in about one third of fatally injured bicyclists aged 15 years or older. OBJECTIVE: To assess the relative risk of fatal and serious bicycling injury according to BAC. DESIGN: Matched case-control study. SETTING AND SUBJECTS: Bicyclists aged 15 years or older who were fatally or seriously injured while riding a bicycle during the day in Maryland in 1985-1997 (cases, n = 124) and bicyclists aged 15 years or older who were interviewed and given a breath test for estimated BAC during roadside surveys that took place in June 1996 through May 1998 at the same site, time of day, day of week, and month of year in which a case bicyclist was injured (controls, n = 342). MAIN OUTCOME MEASURE: Odds ratio of bicycling injury according to estimated BAC. RESULTS: An estimated positive BAC (>/=0.02 g/dL) was detected in 12.9% of the case bicyclists (23.5% of the 34 fatally injured and 8.9% of the 90 seriously injured) compared with 2.9% of the control bicyclists (P<.001). Relative to an estimated BAC of less than 0.02 g/dL, the adjusted odds ratio of bicycling injury was 5.6 (95% confidence interval [CI], 2.2-14.0) for a BAC of 0.02 g/dL or higher and was 20.2 (95% CI, 4.2-96.3) for a BAC of 0.08 g/dL or higher. Rates of helmet use at the time of injury or interview were 5% and 35%, respectively, for those with and without a positive BAC (P =.007). CONCLUSION: Alcohol use while bicycle riding is associated with a substantially increased risk of fatal or serious injury.