How does nighttime alcohol intake affect your heart during sleep? Original paper

Alcohol is associated with several chronic health risks in addition to its well-known negative effects on mental function and sleep.^[1][2] Consuming alcohol prior to sleep can disrupt the normal progression of sleep stages, reduce the time spent asleep, and increase autonomic cardiovascular activity during sleep.^[3]

Alcohol intoxication leads to physiological and behavioral changes the next day (aka a “hangover”). Little is known about whether disturbed sleep may play a role in the morning-after effects of alcohol consumption. Do the impairments in cognitive function and sleep following alcohol intoxication relate to the severity of hangover the next day?

In this randomized controlled crossover study, 31 healthy adults (average age of 25) consumed an alcoholic beverage (1 gram of ethanol per kilogram of body weight for men and 0.85 grams of ethanol per kilogram of body weight for women) or a placebo beverage (fruit juice) between 8 p.m. and 9 p.m. and then slept from 11 p.m. to 7 a.m. One month separated the alcohol and placebo trials.

The participants completed behavioral, mood, and cognitive assessments before, during, and after alcohol consumption and the next morning. Polysomnography (aka sleep study monitoring) was performed continuously during sleep.

The primary outcomes were nocturnal heart rate, total sleep time, sleep efficiency, sleep latency, nighttime arousals, awakenings, and time spent in the different sleep stages (light sleep, deep sleep, and rapid eye movement or REM sleep).

Alcohol consumption increased “low arousal negative” (i.e., woozy, dizzy, wobbly) and “high arousal positive” (i.e., fun, lively, talkative, funny) mood states, increased the urge to drink, and caused higher levels of sedation before sleep. Reaction time, processing speed, and motor control were all reduced after alcohol consumption.

Overnight heart rate increased by 9 beats per minute after alcohol consumption. Total sleep time, sleep efficiency, and time spent in REM sleep all decreased after alcohol consumption, while time spent in deep sleep increased.

The morning after alcohol consumption, “low arousal negative” mood increased, and the urge to drink decreased. Working memory improved in the morning after alcohol consumption.

There was no association between the mood and behavioral effects of alcohol and changes in sleep or nocturnal heart rate. Additionally, the changes in sleep and nocturnal heart rate were not related to next-day mood and behavior. This suggests that the “hyperarousal” caused by presleep alcohol consumption may not explain the morning-after effects, as once previously thought.