Study objectives: To explore the time of day effects of alcohol on sleep, we examined sleep following alcohol administered at four times of day and three homeostatic loads during a 20-hr forced desynchrony (FD) protocol.
Participants: Twenty-six healthy young adults (21-25 yrs) were studied.
Design: Participants were dosed at 4 clock times: 0400 (n = 6; 2 females), 1600 (n = 7; 4 females), 1000 (n = 6; 1 female) or 2200 (n = 7; 2 females). Participants slept 2300 to 0800 for at least 12 nights before the in-lab FD study. Double blind placebo and alcohol (vodka tonic targeting 0.05g% concentration) beverages were each administered three times during FD at different homeostatic loads: low (4.25 or 2.24 hrs awake), medium (8.25 or 6.25 hrs awake), high (12.25 or 10.25 hrs awake) in the 0400 and 1600 or 1000 and 2200 groups, respectively. Sleep was staged and subjected to spectral analysis.
Measurements and results: Breath Alcohol Concentration (BrAC) confirmed targeted maximal levels. At bedtime, BrAC was 0 in the low and medium homeostatic load conditions; however, at high homeostatic load, BrAC was still measurable. Spectral characteristics of sleep were unaffected with alcohol at any time of day. Few alcohol related changes were seen for sleep stages; however, with alcohol given at 0400 at a high homeostatic load there was an increase in wake.
Conclusions: These data lend support to the idea that alcohol may be disruptive to sleep; however, our findings are inconsistent with the idea that a low dose of alcohol is a useful sleep aid when attempting to sleep at an adverse circadian phase.
Keywords: EEG; Sleep; alcohol; forced desynchrony; timing.