[Road traffic crashes, alcohol, meals, sleep and work hours: a case-crossover study at the Emergency Room of Udine,...

In case-crossover studies, useful for assessing the effect of acute transient exposures, each case acts as his/her own control, therefore, interpersonal confounding is controlled for by study. We used such design for studying the effect of the acute consumption of alcohol and meals, and of sleep and work hours on the risk of road traffic crashes. Subjects, enrolled at the Emergency Room (ER) of Udine from 12/3/2007 to 11/3/2008, were a sample of the drivers who arrived alive at the ER after a crash. They were interviewed by trained interviewers, who systematically covered predefined shifts, using a semi-structured questionnaire. The questionnaire collected information on the subjects, vehicles, and crashes, and contained a hourly diary of the exposure to driving, sleeping, working in the 48 hours before the crash and to alcohol and meals 24 hours before the crash. The statistical analysis was based on the matched pair interval approach. The exposures in the hours immediately before the crash (case window) were compared with those in previous hours (control window). Different window durations were chosen for different exposures. The relative risk (RR) of having a crash and 95% confidence intervals (95% CI) were estimated with conditional logistic regression, adjusting for potential confounders such as day of the week and time. We observed a statistically significant two-fold increase in the RR for drivers who had consumed alcohol (even small amounts) and a four-fold increase for those who had worked > 12 ore. The RR was increased by 10 times for drivers who had been awake for at least 16 hours. Meals were not associated with the risk of crash; the findings regarding sleep amount were controversial. In conclusion, the study confirms an increased risk of road crashes after consuming alcohol, even for amounts below the legal limit, and suggests that extended work hours and prolonged wakefulness may increase the risk of crashes.