Sleep restriction, ethanol effects and time of day

Abstract

The sedative and performance-disruptive effects of ethanol as a function of basal level of sleepiness/alertness and circadian time was studied. Ethanol (0.5 g/kg) or placebo was administered to 12 healthy, normal-sleeping men, aged 21 to 45 years, at two different times of the day (09.00 and 16.00 h) after 8 h time in bed (TIB) the previous night and at 16.00 h after 4 h TIB. The Multiple Sleep Latency Test (MSLT) was conducted at 1, 3, 5, and 7 h post-ethanol consumption in a day drinking and in two evening drinking conditions. Auditory vigilance and divided attention performance was assessed 1 and 5 h post-ethanol. A significant difference in MSLT scores was found between the 4-h and 8-h TIB conditions reflecting increased sleepiness. The significant reduction in MSLT scores after morning ethanol was not seen in either of the evening ethanol conditions (8-h or 4-h TIBs). Performance on the auditory vigilance task 1 h post-administration was disrupted by ethanol consumption in the morning, but not in the evening conditions (8-h or 4-h TIBs).