ACEP: Predictors for Fatal Bicycle-Crashes Identified

NEW ORLEANS, Oct. 18 -- A portrait of a fatal bicycle accident involves a male adult rider who has been drinking and has a collision with a car on a high-speed roadway, researchers reported here.

Each of these factors-alcohol, male adult, an accident involving a car, and riding on a high-speed roadway-contribute to the likelihood that a bicycle accident will be fatal, according to a review of a decade's worth of data.

Nonfatal crashes were significantly more common than fatal accidents, and tended to involve younger riders, reported Jonathan LaValley, M.D., of the University of New Mexico in Albuquerque, and colleagues.

They also found that helmets were protective in both fatal and non-fatal crashes, but more than a quarter of all deaths occurred in cyclists who were wearing helmets at the time of the accident, the investigators reported at the American College of Emergency Physicians meeting here.

"Helmets definitely need to be used as much as possible, said co-author David P. Sklar, M.D., chairman of emergency medicine at New Mexico, in an interview."They do protect you when you fall off of a bicycle, but if you get hit by a car, a helmet probably is not going to be an adequate protection."

For the purpose of recommending crash prevention and control measures, the New Mexico group conducted a retrospective review of all fatal and non-fatal bike crashes in New Mexico in over a 10-year period, to see whether they could identify at-risk groups and behavioral factors influencing injuries and deaths.

Using state records and uniform police reports, they identified a total of 73 fatalities and 3,152 injuries caused by motor vehicle/bicycle run-ins.

They computed descriptive characteristics for cyclist ethnicity, age, gender, crash characteristics, and contributing behaviors. They looked at age adjusted injury and fatality rates and calculated proportions and confidence intervals.

The rates were directly age-adjusted to the 2000 U.S. Census, and were expressed as events per one million person-years.

They found that the overall death rate was 3.8 per one million person-years, with native Americans having the highest likelihood of a fatal accident (5.0). Men were nearly 10 times more likely than women to die in a bike crash (relative rate 9.8, 95% confidence interval, 4.5-21.2).

The highest death rates were among adults from ages 30 to 49 years (6.8), and children and adolescents ages 10 to 19 years (4.1).

There were a total of 154 non-fatal injuries per one million person-years, with children up to age 19 having the highest rate, 258 per one million person-years.

Perhaps not surprisingly, non-fatal crashes were less likely to involve cars or trucks (72% vs. 86% of fatal crashes, a difference of 14% [95% CI 4%-21%]).

Behaviors that contributed to crashes included operator inattention, failure to yield, and passing traffic signals or stop signs without stopping.

In a quarter of all fatalities (24.6%), cyclists' blood tested positive for alcohol, and in nearly three-fourths of deaths (71.1%) riders were not wearing a helmet.

Twice as many fatalities occurred in the city as in rural areas (67.1% versus 32.9%, respectively), and significantly more deaths than injuries occurred at night, with 21.9% of fatalities happening after dark, versus. 4.2% of injuries (odds ratio 6.42, 95% CI 3.62-11.4, P<0.001). Significantly more fatalities than injuries also occurred among early-morning bikers (6.8% vs. 1.1%, odds ratio 6.71, 95% CI, 2.66-17.11, P<0.001).

When it came to the type of roadway, the only significant predictor of a fatal crash was whether the accident occurred on an urban artery (as opposed to collector or street), with 31.5% of fatalities occurring on such highways, compared with 21.9% of non-fatal crashes (odds ratio 1.86, 95% CI, 1.14-3.02, P=0.0100).

"The results suggest that we really need to look at different kinds of helmet protection, especially if people start using their bicycles more and more as transportation between home and work," Dr. Sklar said. "As we look at the gas/oil crisis, with more people using their bicycles for transportation, we need to think about safer roadways for bicycles. Unfortunately, streets are pretty much designed for motor vehicles -- they're not designed for pedestrians, for bicyclists, for everybody together."