Although men are three times more likely than women to be killed in car crashes, researchers at the Johns Hopkins Schools of Medicine and Public Health have found that, when the total numbers of crashes are considered, female drivers are involved in slightly more crashes than men. Overall, men were involved in 5.1 crashes per million miles driven compared to 5.7 crashes for women, despite the fact that on average they drove 74 percent more miles per year than did women.
The investigators, who published their results in the July issue of Epidemiology, found that although teenage boys started off badly, with about 20 percent more crashes per mile driven than teenage girls, males and females between ages 20 and 35 were equally at risk of being involved in a crash, and after age 35 female drivers were at greater risk of a crash than their male counterparts.
Lead author Guohua Li, MD, PhD, associate professor of Emergency Medicine at the Johns Hopkins School of Medicine, and of Health Policy and Management at the Johns Hopkins School of Public Health, said, "Although risk-taking behaviors may contribute to the excessive injury mortality among men and younger drivers, up to now age and sex discrepancies in death rates from motor vehicle crashes have not been well understood."
The researchers used 1990 crash statistics gathered by the Fatal Accident Reporting System (FARS), the General Estimates System (GES), and the Nationwide Personal Transportation Survey (NPTS) and applied an innovative method called "decomposition" to break down the data into new categories and weigh the relative contributions of three variables: crash fatality, incidence density (that is, number of crashes per million person-miles) and exposure prevalence (annual average miles driven per driver). Traditionally, the death rate ratio has been considered to be a function of just two factors: fatality rates and accident rates.
The investigators determined that about half of the 3.1-fold difference between the sexes' fatal crash involvement rates was due to the fact that males' crashes were more severe. Another 40 percent was due to the fact that men, who on average drove many more miles than women, thus had a greater opportunity of being in a crash; and 8 percent because of gender differences in "crash incidence density," the number of crashes per million person-miles.
Each year, highway crashes claim about 40,000 lives, cause three million injuries, and cost the nation $140 billion.
The study was supported in part by a grant from the National Institute on Alcohol Abuse and Alcoholism and a grant from the Centers for Disease Control and Prevention.
Co-authors: Gabor Kelen, MD, professor and director, Emergency Medicine, the Johns Hopkins School of Medicine; and Susan P. Baker, PhD, professor of Health Policy and Management, the Johns Hopkins School of Public Health.
Journal
Epidemiology