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Alcohol and Sleep
The average adult sleeps 7.5 to 8 hours every night.
Although the function of sleep is unknown, abundant evidence
demonstrates that lack of sleep can have serious
consequences, including increased risk of depressive
disorders, impaired breathing, and heart disease. In
addition, excessive daytime sleepiness resulting from sleep
disturbance is associated with memory deficits, impaired
social and occupational function, and car crashes (1,2).
Alcohol consumption can induce sleep disorders by disrupting
the sequence and duration of sleep states and by altering
total sleep time as well as the time required to fall asleep
(i.e., sleep latency). This Alcohol Alert explores the
effects of alcohol consumption on sleep patterns, the
potential health consequences of alcohol consumption
combined with disturbed sleep, and the risk for relapse in
those with alcoholism who fail to recover normal sleep
patterns.
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Sleep Structure, Onset, and Arousal
Before discussing alcohol's effects on sleep, it is helpful
to summarize some basic features of normal sleep. A person
goes through two alternating states of sleep, characterized
in part by different types of brain electrical activity
(i.e., brain waves). These states are called slow wave sleep
(SWS), because in this type of sleep the brain waves are
very slow, and rapid eye movement (REM) sleep, in which the
eyes undergo rapid movements although the person remains
asleep.
Most sleep is the deep, restful SWS. REM sleep occurs
periodically, occupying about 25 percent of sleep time in
the young adult. Episodes of REM normally recur about every
90 minutes and last 5 to 30 minutes. REM sleep is less
restful than SWS and is usually associated with dreaming.
Although its function is unknown, REM appears to be
essential to health. In rats, deprivation of REM sleep can
lead to death within a few weeks (3). In addition, a
transitional stage of light sleep occurs at intervals
throughout the sleep period (4).
Sleep was formerly attributed to decreased activity of brain
systems that maintain wakefulness. More recent data indicate
that sleep, like consciousness, is an active process. Sleep
is controlled largely by nerve centers in the lower brain
stem, where the base of the brain joins the spinal cord.
Some of these nerve cells produce serotonin, a chemical
messenger associated with sleep onset (5) and with the
regulation of SWS. Certain other nerve cells produce
norepinephrine, which helps regulate REM sleep and
facilitates arousal (6). The exact roles and interactions of
these and other chemical messengers in orchestrating sleep
patterns are not known (6). Significantly, however, alcohol
consumption affects the function of these and other chemical
messengers that appear to influence sleep.
Alcohol and Sleep in Those Without Alcoholism
Alcohol consumed at bedtime, after an initial stimulating
effect, may decrease the time required to fall asleep.
Because of alcohol's sedating effect, many people with
insomnia consume alcohol to promote sleep. However, alcohol
consumed within an hour of bedtime appears to disrupt the
second half of the sleep period (7). The subject may sleep
fitfully during the second half of sleep, awakening from
dreams and returning to sleep with difficulty. With
continued consumption just before bedtime, alcohol's
sleep-inducing effect may decrease, while its disruptive
effects continue or increase (8). This sleep disruption may
lead to daytime fatigue and sleepiness. The elderly are at
particular risk, because they achieve higher levels of
alcohol in the blood and brain than do younger persons after
consuming an equivalent dose. Bedtime alcohol consumption
among older persons may lead to unsteadiness if walking is
attempted during the night, with increased risk of falls and
injuries (3).
Alcoholic beverages are often consumed in the late afternoon
(e.g., at "happy hour" or with dinner) without further
consumption before bedtime. Studies show that a moderate
dose1 of alcohol consumed as much as 6 hours before bedtime
can increase wakefulness during the second half of sleep. By
the time this effect occurs, the dose of alcohol consumed
earlier has already been eliminated from the body,
suggesting a relatively long-lasting change in the body's
mechanisms of sleep regulation (7,8).
The adverse effects of sleep deprivation are increased
following alcohol consumption. Subjects administered low
doses of alcohol following a night of reduced sleep perform
poorly in a driving simulator, even with no alcohol left in
the body (9,10). Reduced alertness may potentially increase
alcohol's sedating effect in situations such as rotating
sleep-wake schedules (e.g., shift work) and rapid travel
across multiple time zones (i.e., jet lag) (9). A person may
not recognize the extent of sleep disturbance that occurs
under these circumstances, increasing the danger that
sleepiness and alcohol consumption will co-occur.
Alcohol and Breathing Disorders
Approximately 2 to 4 percent of Americans suffer from
obstructive sleep apnea (OSA), a disorder in which the upper
air passage (i.e., the pharynx, located at the back of the
mouth) narrows or closes during sleep (11). The resulting
episode of interrupted breathing (i.e., apnea) wakens the
person, who then resumes breathing and returns to sleep.
Recurring episodes of apnea followed by arousal can occur
hundreds of times each night, significantly reducing sleep
time and resulting in daytime sleepiness. Those with
alcoholism appear to be at increased risk for sleep apnea,
especially if they snore (12). In addition, moderate to high
doses of alcohol consumed in the evening can lead to
narrowing of the air passage (13,14), causing episodes of
apnea even in persons who do not otherwise exhibit symptoms
of OSA. Alcohol's general depressant effects can increase
the duration of periods of apnea, worsening any preexisting
OSA (14).
OSA is associated with impaired performance on a driving
simulator as well as with an increased rate of motor vehicle
crashes in the absence of alcohol consumption (9,10). Among
patients with severe OSA, alcohol consumption at a rate of
two or more drinks per day is associated with a fivefold
increased risk for fatigue-related traffic crashes compared
with OSA patients who consume little or no alcohol (15). In
addition, the combination of alcohol, OSA, and snoring
increases a person's risk for heart attack, arrhythmia,
stroke, and sudden death (16).
Age-Related Effects and the Impact of Drinking
Little research has been conducted on the specific effects
of alcohol on sleep states among different age groups. Scher
(17) investigated the effects of prenatal alcohol exposure
on sleep patterns in infants. Measurements of brain
electrical activity demonstrated that infants of mothers who
consumed at least one drink per day during the first
trimester of pregnancy exhibited sleep disruptions and
increased arousal compared with infants of nondrinking
women. Additional studies revealed that infants exposed to
alcohol in mothers' milk fell asleep sooner but slept less
overall than those who were not exposed to alcohol (18). The
exact significance of these findings is unclear.
Normal aging is accompanied by a gradual decrease in SWS and
an increase in nighttime wakefulness. People over 65 often
awaken 20 times or more during the night, leading to sleep
that is less restful and restorative (3). Age-related sleep
deficiencies may encourage the use of alcohol to promote
sleep, while increasing an older person's susceptibility to
alcohol-related sleep disturbances (3,19). Potential sources
of inconsistency among study results include different doses
of alcohol employed and failure to screen out subjects with
preexisting sleep disorders (3).
Success
can be achieved through
drug intervention,
drug rehabilitation and entering
drug treatment.
Effects of Alcohol on Sleep in Those With Alcoholism
Active Drinking and Withdrawal. Sleep disturbances
associated with alcoholism include increased time required
to fall asleep, frequent awakenings, and a decrease in
subjective sleep quality associated with daytime fatigue
(3). Abrupt reduction of heavy drinking can trigger alcohol
withdrawal syndrome, accompanied by pronounced insomnia with
marked sleep fragmentation. Decreased SWS during withdrawal
may reduce the amount of restful sleep. It has been
suggested that increased REM may be related to the
hallucinations that sometimes occur during withdrawal. In
patients with severe withdrawal, sleep may consist almost
entirely of brief periods of REM interrupted by numerous
awakenings (3,20).
Recovery and Relapse. Despite some improvement after
withdrawal subsides, sleep patterns may never return to
normal in those with alcoholism, even after years of
abstinence (3,21). Abstinent alcoholics tend to sleep
poorly, with decreased amounts of SWS and increased
nighttime wakefulness that could make sleep less restorative
and contribute to daytime fatigue (22). Resumption of heavy
drinking leads to increased SWS and decreased wakefulness.
This apparent improvement in sleep continuity may promote
relapse by contributing to the mistaken impression that
alcohol consumption improves sleep (23-25). Nevertheless, as
drinking continues, sleep patterns again become disrupted
(3).
Researchers have attempted to predict relapse potential
using measures of sleep disruption. Gillin and colleagues
(26) measured REM sleep in patients admitted to a 1-month
alcoholism treatment program. Higher levels of REM predicted
those who relapsed within 3 months after hospital discharge
in 80 percent of the patients. A review of additional
research (3) concluded that those who eventually relapsed
exhibited a higher proportion of REM and a lower proportion
of SWS at the beginning of treatment, compared with those
who remained abstinent. Although additional research is
needed, these findings may facilitate early identification
of patients at risk for relapse and allow clinicians to
tailor their treatment programs accordingly.
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