Drinking alcohol and bicycling don't mix well, say Johns Hopkins researchers, whose study of 466 Maryland bicyclists found that a third of fatally injured riders had elevated blood alcohol levels at the time of their accident. In addition, a blood alcohol concentration of 0.08 grams per deciliter--the legal level of drunkenness in most states--was found to increase the rider's risk of fatal or serious injury by 2,000 percent.

The report, in the Feb. 21 issue of the Journal of the American Medical Association, also indicates that helmet wearing declines with drinking. Researchers studied the records of 124 injured bicyclists obtained from the Office of the Chief Medical Examiner of Maryland and the trauma registry of the University of Maryland Medical Center. They also visited each accident site the same month, date and time that the biker was injured and tested 342 passing bicyclists for breath alcohol.

By comparing the alcohol levels in the two groups, researchers estimated that blood alcohol concentrations (BAC) of 0.02 g/dL and 0.08 g/dL are associated, respectively, with a sixfold and 20-fold increased risk of fatal or serious bicycling injury. On average, one drink can lead to a BAC of 0.02 g/dL, while four to five drinks can lead to a BAC of 0.08 g/dL.

Only 5 percent of the injured who had been drinking wore helmets. Thirty percent of the injured bicyclists who had elevated blood alcohol levels also had a history of DWI (driving while intoxicated) citations; some probably used bicycles as a form of transportation because their driver's licenses had been suspended, the authors said.

Alcohol may play an even greater role than indicated by this study, the researchers said, since the group did not look at bicycle injuries occurring at night, when 56 percent of fatal bicycling injuries and 32 percent of serious bicycling injuries occur.

"Riding a bike requires a higher level of psychomotor skills and physical coordination than driving a car, so alcohol has an even stronger effect on bicyclists than drivers," says Guohua Li, associate professor of emergency medicine and lead author of the study. "It's a double jeopardy. Those who ride under the influence are most in need of protection, yet in our study, they were least likely to wear helmets."

An alarming trend, researchers note, is that while the number of fatal bicycle accidents in children has decreased by 70 percent since 1975, it has increased in adults by about 65 percent during the same time period.

The helmet laws that worked well for children should be extended to adult bicyclists, says Susan P. Baker, another author of the study and professor of health policy and management at the School of Public Health.

"We are especially concerned because helmet laws do not cover adults, who have the highest death rates, are the most likely to have been drinking and are the least likely to wear helmets," Baker says. "Alcohol abuse and bicycling is an increasing public health problem that warrants more enforcement."

The study was funded by grants from the National Institutes of Health and the Centers for Disease Control and Prevention.