Impairment due to combined sleep restriction and alcohol is not mitigated by decaying breath alcohol concentration or...

Epidemiological and laboratory-based driving simulator studies have shown the detrimental impact of moderate, legal levels of alcohol consumption on driving performance in sleepy drivers. As less is known about the time course of decaying alcohol alongside performance impairment, our study examined impairment and recovery of performance alongside decaying levels of alcohol, with and without sleep restriction.

Sixteen healthy young males (18-27 years) underwent 4 counterbalanced conditions: Baseline, Alcohol (breath alcohol concentration [BrAC] < 0.05%), Sleep Restriction (5 hr time in bed), and Combined. Participants consumed alcohol (or control drink) ~4.5 hr post wake (12:30 p.m.). To test on the descending limb of alcohol, attention and vigilance test batteries commenced 1 hr after consumption and were completed every 30 min for 2 hr (1:30 p.m.-3:30 p.m.).

The Combined condition impaired subjective and objective sleepiness. Here, performance deficits peaked 90 min after alcohol consumption or 30 min after the BrAC peak. Performance did not return to baseline levels until 2.5 hr following consumption, despite receiving rest breaks in between testing.

These findings suggest that (a) falling BrACs are an inadequate guide for performance/safety and (b) rest breaks without sleep are not a safety measure for mitigating performance impairment when consuming alcohol following restricted sleep.