Ebrahim IO, Shapiro CM, Williams AJ, Fenwick PB. Alcohol and sleep I: Effects on normal sleep. Alcohol Clin Exp Res 2013;doi: 10.1111/acer.12006. [Epub ahead of print]
This review provides a qualitative assessment of all known scientific studies on the impact of alcohol ingestion on nocturnal sleep in healthy volunteers. At all dosages, alcohol causes a reduction in sleep onset latency, a more consolidated first half sleep and an increase in sleep disruption in the second half of sleep. The effects on rapid eye movement (REM) sleep in the first half of sleep appear to be dose related with low and moderate doses showing no clear trend on REM sleep in the first half of the night whereas at high doses, REM sleep reduction in the first part of sleep is significant. Total night REM sleep percentage is decreased in the majority of studies at moderate and high doses with no clear trend apparent at low doses. The onset of the first REM sleep period is significantly delayed at all doses and appears to be the most recognizable effect of alcohol on REM sleep followed by the reduction in total night REM sleep.
The majority of studies, across dose, age and gender, confirm an increase in slow wave sleep (SWS) in the first half of the night relative to baseline values. The impact of alcohol on SWS in the first half of night appears to be more robust than the effect on REM sleep and does not appear to be an epiphenomenon REM sleep reduction. Total night SWS is increased at high alcohol doses across gender and age groups.
Anything that affects sleep is of great interest to the public. As pointed out by the authors, the earliest scientific publication relating alcohol intake to sleep was in 1883, and there have been many reports since. The present paper summarizes data from 27 experiments in normal humans that have been published since the 1980s; subjects were not people being evaluated for sleep disorders.
The paper reviews studies on the administration of small (up to about two typical drinks), moderate (the equivalent of about 2-4 drinks), and large (more than about 4 drinks) amounts of alcohol in the evening, generally between 30 and 60 minutes before subjects retire into a laboratory chamber where the sleep pattern is monitored (time to get to sleep, degree of awakening, REM sleep, etc.). A few studies reviewed the effects when alcohol was administered in the afternoon, judging its effects on both an afternoon nap and sleep in the evening.
Specific comments on the paper: Forum members considered this to be a well-done report, and while not experts on alcohol and sleep, members thought this report was especially interesting and useful. Stated reviewer Orgogozo, “This is a good review in a somewhat neglected subject. Sleep specialists consider it important since sleep disturbances contribute to the risk of accidents (day somnolence) and to the cardiovascular risk associated with lack of sleep, through hypertension, fattening, metabolism, and a worsening of sleep apneas.”
Among the studies reviewed by this paper, the large majority were evaluating the effects of large amounts of alcohol, ≥ 75 mg/kg of body weight (for an 80 kg person, this would be 60 grams or more of alcohol; no data are presented on the speed with which the alcohol was administered, whether it was with any food, etc.). All of these studies showed a reduction in the time required to fall asleep and most showed less awakening after falling asleep. However, there was a longer period before REM sleep began and, over the entire night, all studies showed a reduction in REM sleep. While most scientists believe that REM sleep has favorable health effects, mechanisms for such an effect are poorly understood.
For subjects given moderate amounts of alcohol, effects were much less; the authors report that the most significant findings were a shorter latency period before falling asleep and less awakening from sleep. More non-REM sleep occurred later in the night. For subjects given the lowest amount of alcohol, the most consistent findings were faster falling asleep and less awakening in the first part of the sleep period. Later in the night, there were inconsistent results regarding non-REM sleep. Alcohol given in the afternoon had less effect on nocturnal sleep patterns.
Forum reviewer Lanzmann-Petithory considered this to be an interesting and worthwhile paper. “It is consistent with moderate intake recommendations, as there is no effect with low intake except on sleep onset latency (decreased, sleeping drug effect due to anxiolytic effect of alcohol); the wake after sleep onset is increased during the second part of the night, possibly due to diuretic effect of alcohol and decrease of its anxiolytic effects. However, their ‘moderate’ doses are quite high. In fact, their low level can go up to 0.49 g/kg, that is to say for a 80 kg men, 40 g of alcohol, that represents about 416 ml of 12°wine that is not exactly a low intake (a liter of 12% wine contains 96 g of alcohol).
“It has been shown in clinical studies that elderly patients may sleep better after a small amount of alcohol (Mishara BL, Kastenbaum R, Baker F, Patterson RD. Alcohol effects in old age: an experimental investigation. Soc Sci Med 1975; 9:535-547). In another trial with wine in mental institutions, the same authors reported dramatic reduction in chloral hydrate intake to induce sleep with about 160 ounces of wine/week (Mishara BL, Kastenbaum R. Wine in the treatment of long-term geriatric patients in mental institutions. J Am Geriatr Soc 1974;22:88-94.) A question remains: to sleep better, what kind of alcoholic beverage is best? The present study did not have data on specific beverages given. I have seen some patients who report palpitations and sleep disorders after white wine, but I have no explanation about this phenomena.
“The main message appears to be that light drinking has little overall effect on sleep but what the authors call ‘moderate’ dose alcohol (0.5 to 0.74 mg/kg, equivalent to between 2 and 4 standard drinks) and greater amounts of alcohol may interfere with sleep patterns.”
Said reviewer Skovenborg: “I agree with other comments that this is a thorough and well-done review of the effects of alcohol on sleep. One thing I find hard to understand, and not in accordance with the personal experience of me (and my friends) is that a single drink at bedtime should disrupt the sleep and give frequent awakenings for the second half of the night.”
This paper provides an excellent review of intervention studies since the 1980s on the effects of alcohol consumption on sleep. The study finds that the time required to fall asleep, and sleep patterns in the first part of the night, tend to be improved by alcohol. However, the authors conclude that “The onset of the first REM sleep period is significantly delayed at all doses and appears to be the most recognizable effect of alcohol on REM sleep, followed by the reduction in total night REM sleep.” Slow-wave sleep is more common and REM sleep less common after alcohol.
The studies reviewed in this report were intervention studies among mainly young normal subjects, not people with sleep disorders. Other studies have demonstrated that small amounts of alcohol given in the evening to the elderly may improve sleep, and reduce the need for sleep-inducing medications. Overall, the data reviewed in this paper suggest that small amounts of alcohol in the evening have few adverse effects on sleep, and relate to earlier onset of sleep and less awakening in the first part of the night. Larger amounts of alcohol tend to make the onset of sleep faster, but may have adverse overall effects on sleep patterns. It appears that all levels of alcohol consumption just prior to retiring are associated with a shorter duration of REM sleep throughout the night.
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Contributions to this critique were provided by the following members of the International Scientific Forum on Alcohol Research:
Dominique Lanzmann-Petithory,MD, PhD, Nutrition/Cardiology, Praticien Hospitalier Hôpital Emile Roux, Paris, France
Fulvio Ursini, MD, Dept. of Biological Chemistry, University of Padova, Padova, Italy
Arne Svilaas, MD, PhD, general practice and lipidology, Oslo University Hospital, Oslo, Norway
Erik Skovenborg, MD, Scandinavian Medical Alcohol Board, Practitioner, Aarhus, Denmark
Jean-Marc Orgogozo, MD, Professor of Neurology and Head of the Neurology Divisions, the University Hospital of Bordeaux, Pessac, France
Harvey Finkel, MD, Hematology/Oncology, Boston University Medical Center, Boston, MA, USA
Ulrich Keil, MD, PhD, Institute of Epidemiology and Social Medicine, University of Münster, Münster, Germany
R. Curtis Ellison, MD, Section of Preventive Medicine & Epidemiology, Boston University School of Medicine, Boston, MA, USA