Association of helmet use with death in motorcycle crashes: a matched-pair cohort study.

The association of helmet use with death in a motorcycle crash can be estimated using matched-pair cohort methods. By estimating effects among naturally matched pairs on the same motorcycle, one can account for potential confounding by motorcycle characteristics, crash characteristics, and other factors that may influence the outcome. The authors used Fatality Analysis Reporting System data, from 1980 through 1998, for motorcycles that crashed with two riders and either the driver or the passenger, or both, died. For their main analysis, the authors estimated the relative risk of death using conditional Poisson regression. The relative risk of death, accounting for the matching on motorcycle and adjusted for age, sex, and seat position, for a helmeted rider compared with an unhelmeted rider was 0.61 (95% confidence interval: 0.54, 0.70). The authors suggest that conditional Poisson regression is useful for the analysis of traffic crash data, where occupants are naturally matched in a vehicle and where crash-related confounders may be difficult or impossible to measure.