The study, authored by Andrew Vakulin, of the Adelaide Institute for Sleep Health at Repatriation General Hospital in Australia, focused on 21 healthy young men, aged 18-30 years, who all had normal sleep patterns and no sleep disorders. The participants completed a 70-minute simulated driving session, which included steering deviation, braking reaction time, and number of collisions, and underwent repeated measures with four experimental conditions: normal sleep without alcohol, sleep restriction alone (four hours) and sleep restriction in combination with two different low BACs (0.025 g/dL and 0.035 g/dL).
According to the results, steering deviation increased significantly when sleep restriction was combined with the higher dose alcohol. This combination also resulted in a greater subjective sleepiness and negative driving performance ratings compared to control or sleep restriction alone.
“The ability to keep the car in the middle of the lane is critical to safe driving, and is one of the more sensitive measures of driving impairment,” said Vakulin. “Although steering deviation was not significantly affected by sleep restriction alone, alcohol at a BAC as low as 0.025 g/dL in combination with sleep restriction was sufficient to significantly impair steering ability. This combination may considerably reduce the threshold for safe driving, as suggested by the steering deviation data and an increase in off-road collisions following sleep restriction and alcohol ingestion in this study.”
Source: SLEEP Volume: 30 Issue:10 Pages:1327-1333