The contribution of alcohol to serious car crash injuries.

BACKGROUND: Alcohol impairment of drivers is considered the most important contributing cause of car crash injuries. The burden of injury attributable to drinking drivers has been estimated only indirectly.
METHODS: We conducted a population-based case-control study in Auckland, New Zealand between April 1998 and July 1999. Cases were 571 car drivers involved in crashes in which at least 1 occupant was admitted to the hospital or killed. Control subjects were 588 car drivers recruited on public roads, representative of driving in the region during the study period. Participants completed a structured interview and had blood or breath alcohol measurements.
RESULTS: Drinking alcohol before driving was strongly associated with injury crashes after controlling for known confounders. This was true for several measures of alcohol consumption: for self-report of 2 or more 12-g alcoholic drinks in the preceding 6 hours compared with none, the odds ratio (OR) was 7.9 (95% confidence interval = 3.4-18); for blood alcohol concentration 3 to 50 mg/100 mL compared with <3 mg/100 mL, the OR was 3.2 (1.1-10); and for blood alcohol concentration greater than 50 mg/100 mL compared with <3 mg/100 mL, the OR was 23 (9-56). Approximately 30% of car crash injuries in this population were attributable to alcohol, with two-thirds involving drivers with blood alcohol concentration in excess of 150 mg/100 mL. Equal proportions of alcohol-related injury crashes were attributable to drivers with blood alcohol concentrations of 3 to 50 mg/100 mL as those with levels of 51 to 150 mg/100 mL.
CONCLUSION: Evidence about the proportion of crashes attributable to drivers at different blood alcohol concentrations can inform the prioritization of interventions that target different groups of drivers. These data indicate where there is the most potential for reduction of the injury burden.