Alcohol is the most commonly consumed psychoactive substance worldwide, and its effects on brain function and behavior, particularly on sleep, have long been a subject of scientific inquiry. A recent study published in the journal Sleep sheds new light on how alcohol consumption before sleep over consecutive nights can significantly alter sleep architecture, offering a more nuanced understanding of its impact on our nightly rest.
Previous research has established that alcohol can expedite sleep onset, with a notable percentage of adults in the United States using alcohol as a sleep aid. However, these studies often faced limitations, such as small and homogenous participant samples and a lack of control over participants’ sleep and alcohol use patterns prior to the study. Moreover, the cumulative effects of drinking alcohol over consecutive nights were largely unexplored, leaving a gap in our understanding of its impact on sleep quality and structure.
To address these gaps, the researchers combined experimental alcohol administration with detailed overnight physiological sleep studies. The researchers focused on understanding how consecutive nights of alcohol consumption affect sleep architecture.
“We are primarily interested in looking at “next day” cognitive consequences of serial nights of alcohol use. These sleep data provide a novel picture of the impact of alcohol by looking at the sleep structure in a fine-grained manner,” said study author Mary A. Carskadon, a professor at the Alpert Medical School of Brown University and director of the E.P. Bradley Hospital Sleep Research Laboratory.
The study involved thirty healthy adult participants with moderate drinking habits, ensuring a diverse sample in terms of age, gender, and race. Participants underwent a rigorous pre-study screening process, including actigraphy to monitor sleep patterns, and were required to maintain a stable sleep schedule in the days leading up to the laboratory sessions.
The core of the study took place over two three-night laboratory sessions, with each session separated by approximately four days. During these sessions, participants’ sleep was monitored using polysomnography (PSG), a comprehensive recording of the biophysiological changes that occur during sleep. This included measurements of brain waves, eye movements, and muscle activity, providing a detailed picture of sleep architecture.
On each night of the lab sessions, participants consumed either an alcoholic beverage or a placebo mixer before sleep, with the order of these conditions randomized across participants. The alcoholic beverage’s strength was calibrated to target a breath alcohol concentration of 0.08 mg/L, ensuring a consistent level of intoxication across participants. Sleep was then recorded using PSG, allowing the researchers to observe the immediate effects of alcohol consumption on sleep architecture.
One of the key findings was that alcohol consumption before sleep led to an increase in slow wave sleep (SWS) during the first third of the night. SWS, often referred to as deep sleep, is crucial for physical restoration and memory consolidation. The initial boost in SWS suggests that alcohol can deepen sleep in its early phases, which aligns with the common perception of alcohol as a sleep inducer.
This effect was consistently observed across all three nights of alcohol consumption, indicating a direct impact of alcohol on promoting deep sleep during the initial part of the sleep episode.
On the other hand, the study found a decrease in rapid eye movement (REM) sleep during the first third of the night following alcohol consumption. REM sleep is associated with dreaming, memory processing, and emotional regulation. The reduction in REM sleep suggests that alcohol disrupts the sleep cycle’s natural progression, potentially impacting cognitive functions and emotional health.
This decrease in REM sleep was most pronounced on the first night of alcohol consumption, with a lessening effect over subsequent nights, suggesting a degree of adaptation or tolerance developing over consecutive nights of drinking.
The research also highlighted increased sleep fragmentation and wakefulness during the second half of the sleep episode on nights when alcohol was consumed. This disruption is attributed to several factors, including alcohol-induced diuresis leading to more frequent bathroom trips, night sweats, and a “wakeful rebound” as the body metabolizes the alcohol.
Such disturbances can detract from the restorative quality of sleep, leading to feelings of fatigue and impaired cognitive function the following day.
A noteworthy aspect of the study’s findings is the evidence of the body’s adaptation to consecutive nights of alcohol consumption. While the initial night of drinking saw the most significant disruptions in sleep architecture, these effects became less pronounced over the following two nights.
This adaptation suggests that the body may develop a tolerance to some of alcohol’s sleep-altering effects, particularly regarding REM sleep. Despite this adaptation, the cumulative impact of disrupted sleep across multiple nights could still have significant implications for overall well-being and cognitive performance.
Employing generalized additive models (GAMs) for a high-resolution analysis, the researchers were able to document the nuanced dynamics of sleep architecture affected by alcohol. This approach revealed specific periods during the night when the impact of alcohol on SWS and REM sleep was most pronounced, providing a detailed temporal map of alcohol’s effects on sleep. Such fine-grained analysis underscores the complexity of sleep as a process and highlights the multifaceted ways in which alcohol can alter this process.
These findings contribute to a more comprehensive understanding of alcohol’s role in sleep dynamics and underscore the importance of considering the implications of regular alcohol consumption on sleep quality and overall health.
“When you drink before going to bed, you modify your sleep,” Carskadon told PsyPost. “The effects differ on consecutive nights; however, some trace of alcohol continues. We note as well that our study design provided plenty of time (8 to 8.5 hours) for people to sleep after drinking. Many people will curtail their sleep after drinking and therefore the impact of alcohol may differ.”
Despite its strengths, the study has some limitations. The sample size, while diverse, was relatively small, and the findings may not generalize to all populations. Additionally, the controlled laboratory environment differs significantly from real-world settings, where factors such as stress and environmental noise can also impact sleep.
Looking ahead, the study’s authors call for further research to explore the long-term effects of consecutive nights of alcohol consumption on sleep, as well as its implications for cognitive function and overall health. They also emphasize the need for studies with larger and more diverse participant samples to fully understand the breadth of alcohol’s impact on sleep across different populations.
The study, “Altered sleep architecture following consecutive nights of pre-sleep alcohol,” was authored by Katie S. McCullar, David H. Barker, John E McGeary, Jared M. Saletin, Caroline Gredvig-Ardito, Robert M. Swift, and Mary A. Carskadon.
