Ethanol and sleep loss: a "dose" comparison of impairing effects

Studies to assess the risks associated with sleep loss relative to the well-documented risks of alcohol are limited in number and design. This study compared the "dose"-related sedative, performance-impairing, and amnestic effects of sleep loss to those of ethanol ingestion.

Mixed-design experiment with random assignment to a sleep loss (n=12) or ethanol (n=20) group, with each participant assessed under 4 conditions.

Thirty-two healthy normal adult volunteers, aged 21 to 35 years.

In sleep loss, participants had 8, 6, 4, and 0 hours time in bed, producing 0, 2, 4, and 8 hours of sleep loss. For ethanol, participants ingested 0.0 g/kg, 0.3 g/kg, 0.6 g/kg, and 0.9 g/kg ethanol from 8:30 AM to 9:00 AM after 8 hours of time in bed the previous night. Each participant received his or her 4 doses of ethanol or sleep loss in a Latin square design with 3 to 7 days between doses.

All subjects completed the Multiple Sleep Latency Test (MSLT) at 9:30 AM, 11:30 AM, 1:30 PM, 3:30 PM, and 5:30 PM and a performance battery at 10:00 AM, 12:00 NOON, 2:00 PM, and 4:00 PM consisting of memory, psychomotor vigilance, and divided attention tests.

Ethanol and sleep loss reduced the average daily sleep latency on the MSLT, both as a linear function of dose, with sleep loss in hours being 2.7 times more potent than ethanol in grams per kilogram. Ethanol and sleep loss also slowed reaction time on the psychomotor vigilance test in a linear dose-related function with the 2 being equipotent in their impairing effect. On the divided attention test, tracking deviations were increased by both ethanol and sleep loss in an equipotent and linear dose-related function. Memory recall was reduced in a linear dose-related function by both ethanol and sleep loss with ethanol being slightly more potent. Finally, sleep loss doses produced a linear decrease in self-rated quality of performance, while only at the highest ethanol dose was performance rated as poorer.

At the studied doses, sleep loss was more potent than ethanol in its sedative effects but comparable in effects on psychomotor performance. Ethanol produced greater memory deficits, and subjects were less aware of their overall performance impairment.