Racial/ethnic disparities in the self-reported number of drinks in 2 hours before driving becomes impaired

Objectives. We used data on self-reported impaired driving and the number of drinks the person states he or she can have in 2 hours before impairment to evaluate predictors of individuals' impairment thresholds by race/ethnicity. Methods. Data come from the 2000, 2005, and 2010 US National Alcohol Surveys, with oversamples of Black and Hispanic populations. We estimated negative binomial models overall, by gender, and for those who reported impaired driving. Analyses focused primarily on 8553 respondents who drank alcohol and drove a car in the past year. Results. In models that controlled for relevant available measures including body weight, sociodemographics, and drinking patterns, we found perceived impairment thresholds to be 30.3% (95% confidence interval = 23%, 38%) higher for Black drinkers and 26.3% (95% confidence interval = 18%, 35%) higher for Hispanic drinkers compared with White drinkers. Conclusions. The greater number of standard drinks before perceived impairment reported by Black and Hispanic drivers implies a likely relative underreport of impaired driving and potentially higher severity of impairment when driving relative to White drivers.