According to the National Highway Traffic Safety Administration (NHTSA), 2.5% of fatal motor vehicle crashes (approximately 730 in 2009) and 2.0% of all crashes with nonfatal injuries (approximately 30,000 in 2009) involve drowsy driving (1). However, although data collection methods make it challenging to estimate the number of crashes that involve drowsy drivers, some modeling studies have estimated that 15% to 33% of fatal crashes might involve drowsy drivers (2,3). Fatalities and injuries are more likely in motor vehicle crashes that involve drowsy driving compared with non-drowsy driving crashes (1,4). To assess the state-level self-reported prevalence of falling asleep while driving, CDC analyzed data from a set of questions about insufficient sleep administered through the Behavioral Risk Factor Surveillance System (BRFSS) during 2009–2010. Among 147,076 respondents in 19 states and the District of Columbia (DC),* 4.2% reported having fallen asleep while driving at least one time during the previous 30 days. Reports of falling asleep while driving were more common among adults who reported usually sleeping ≤6 hours per day, snoring, or unintentionally falling asleep during the day compared with other adults who did not report these characteristics. Drivers should avoid driving while drowsy and learn the warning signs of drowsy driving.
BRFSS is a state-based, random-digit–dialed telephone survey of noninstitutionalized adults aged ≥18 years that is administered by state health departments each year in collaboration with CDC. Based on Council of American Survey and Research Organizations (CASRO) guidelines, response rates† for the states that used the optional sleep questions during 2009–2010 had a median of 52.1% and ranged from 39.1% (Oregon in 2010) to 68.8% (Nebraska in 2010).
Respondents were asked, “During the past 30 days, have you ever nodded off or fallen asleep, even just for a brief moment, while driving?” Drowsy driving was defined as those with an affirmative response, whereas no drowsy driving included those who responded “no,” “don’t drive,” “don’t have a license,” or “don’t know/not sure.” Respondents also were asked, “On average, how many hours of sleep do you get in a 24-hour period?” “Do you snore?” “During the past 30 days, for about how many days have you felt you did not get enough rest or sleep?” and “During the past 30 days, for about how many days did you find yourself unintentionally falling asleep during the day?” Age-adjusted prevalence of falling asleep while driving and 95% confidence intervals (CIs) were calculated by state, and by selected sociodemographic and other sleep-related characteristics. For comparisons of prevalence between subgroups, statistical significance (p<0.05) was determined by using t-tests. All indicated differences between subgroups are statistically significant.
Among 147,076 respondents, 4.2% (unadjusted prevalence = 4.1%) reported having fallen asleep while driving during the previous 30 days (Table 1). Men were more likely to report drowsy driving than women (5.3% versus 3.2%). Drowsy driving prevalence decreased with age, from >4.9% among adults aged 18–44 years to 1.7% among those aged ≥65 years. Non-Hispanic whites were less likely to report drowsy driving than other racial/ethnic groups (3.2% versus 6.1% for non-Hispanic blacks, 5.9% for Hispanics, and 6.0% for persons of other race/ethnicity). Retired respondents (1.0%), students or homemakers (2.1%), and unemployed respondents (3.1%) were less likely to report drowsy driving than those who were employed (5.1%) or unable to work (6.1%). Educational attainment was not associated with drowsy driving. Among the states that used the sleep module, drowsy driving prevalence ranged from 2.5% in Oregon to 6.1% in Texas.
Drowsy driving was associated with other sleep-related characteristics. Adults who reported frequent insufficient sleep, a daily sleep duration of ≤6 hours, snoring, or unintentionally falling asleep during the day reported drowsy driving more frequently than those who did not report those characteristics (Table 2). Short sleep duration (≤6 hours) and snoring, suggestive of obstructive sleep apnea, each were related independently to drowsy driving (Figure).