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Research report

Cumulative effects of lack of sleep and a legal BAC in young drivers

Globally, alcohol-impaired driving is one of the leading causes of road traffic accidents (RTA) among young drivers, and Québec is no exception. On the other hand, lack of sleep, the third leading cause of road deaths in Québec, is common among young adults, which could increase their vulnerability on the road, even at low legal blood alcohol concentrations (BAC). The scientific literature does not explain how sleep deprivation and low legal BAC increase the risk of RTA among young people, nor how age and gender can be additional vulnerability factors.

The findings will be used for policy development and public health interventions.

Our study therefore aims to investigate the effects of sleep deprivation combined with low legal BAC on driving performance in young drivers, addressing the two most significant risk factors for RTA in Québec.

The results indicate that sleep deprivation negatively affects cognitive function to a degree equivalent to the consumption of enough alcohol to achieve a BAC of about .05%. Sleep deprivation significantly affects executive functions, particularly those related to high-risk decision-making. Alcohol consumption, even at levels below the legal limit (BAC ≈ .03%) for drivers with a regular license, affects behavioural impulsivity. The combination of a low dose of alcohol and sleep deprivation affects the ability to drive safely in a manner comparable to slightly higher BAC levels that are considered illegal in many countries.

The findings will be used for policy development (e.g. the extension of Zero Tolerance, restrictions on night-time driving) and public health interventions (e.g. targeted education).


Main researcher: Thomas G. Brown, Douglas Mental Health University Institute

Original title: Les effets cumulatifs du manque de sommeil et d'un taux légal d'alcoolémie sur la conduite des jeunes conducteurs : l'influence de l'âge, du sexe et des facteurs cognitifs

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