The Individual and Combined Effects of Alcohol Consumption and Sleep Deprivation on Cognitive Functioning
Anna Kroncke, Megan Shaw, Erin Williams,
Elizabeth Winter, JustinWright
Sleep deprivation and alcohol consumption affect cognitive abilities both separately and simultaneously. Surprisingly, though the effects of alcohol intoxication and sleep deprivation are generally similar when observed singularly, however when combined, the effects are varied based on blood alcohol content and length of sleep deprivation.
Effects of Alcohol on Cognitive Ability
Detriments to cognitive functioning have been successfully linked to the usage of alcohol and other drugs. However, the precise makeup of the cognitive impairment caused by alcohol still remains confusing and controversial. Much of the disagreement comes from a lack of thorough description by researchers and the large number of different tests and assessment programs used to evaluate cognitive functioning within an experimental subject (Nixon, 1995).
In recent years, a new approach called the Neurocognitive Assessment Approach has been applied to the studies of chronic alcohol effects. This new approach centers on the particular processes underlying cognitive functioning (e.g. perceiving, learning, and remembering information). This method would have subjects memorize a story, associate pairs of items, or identify a target. The assessment approach would then assess alcohol’s differential effects on processes such as the perception, encoding, or retrieval of information in comparison to a control group (Nixon, 1995).
The studies have shown that detoxified alcoholics frequently demonstrated long-lasting deficits in four domains: abstract thinking and problem solving skills, verbal skills and/or memory, perceptual-motor skills, and visuospatial skills (Tivis, 1995). Whereas alcohol related deficits in verbal skills appear less frequently. This may be attributed to the fact that typical verbal tasks are often over-practiced skills. That is, verbal tasks are performed thousands of times daily in many different situations without conscious awareness of ‘practicing’ (Nixon, 1995).
Another set of studies used to examine the cognitive effects of alcohol use were the Acute Alcohol Administration tests. These studies focus on tasks that assess performance of functions relevant to driving and other practical skills. Therefore, reaction time and response accuracy were of particular interest in these experiments (Nixon, 1995).
Moskowitz and Robinson reviewed 158 studies that considered nine performance measures which included: reaction time, tracking, vigilance, divided attention, visual function, information processing, perception, psychomotor skills, and driving. Of these nine conditions, they found that selective attention provided the most sensitive measure of impairment. Sixty percent of the tested subjects displayed obvious impairment on selective attention tasks with a Blood Alcohol Content (BAC) at or below 0.05%. Although the other tasks demonstrated some impairment at this BAC level, they were not as severe (Nixon, 1995).
Some of the other findings of the acute alcohol experiments found that the effects of alcohol are greater on tasks or processes demanding attention or effort ("controlled" processes) than on tasks or processes making few attentional demands ("automatic" processes") (Sutker, 1982). In addition, 70% to 80% of the studies found that BAC’s at or below 0.04% had significant effects on intoxication ratings and on the performance of controlled tasks (Nixon, 1995).
Other researchers have suggested that acute alcohol administration has a global effect on cognitive functioning. Steele and Josephs have suggested that alcohol consumption produces a "myopic" effect, allowing the drinker to focus attention only on the most salient characteristics of any given situation and to disregard the consequence of other aspects. They observed how much time intoxicated subjects spent reading adjectives that described positive or negative personality traits of the subjects themselves (i.e. were salient) or of another person (i.e. were nonsalient). The study found that subjects spent significantly more time attending to personally salient, negative traits than they did to other types of traits (Nixon, 1995).
Sleep Deprivation and Cognitive Abilities
There has been much discussion in the past few years concerning the effects of sleep deprivation on every day functioning. One group which may be affected by lack of sleep is children, since most schools start early in the morning, standardized tests are given early in the morning, etc. which may prevent a good night’s sleep.
In 1998, a study was done to examine the effects of a night of acute sleep restriction on cognitive function (Randazzo, Muehlbach, Schweitzer, & Walsh, 1998). A sleep-deprived group was only allowed 5 hours in bed, and the control group was allowed 11 hours in bed. The study found that in tasks requiring repetition and less creativity, sleep deprived children scored similarly to the control group of students. However, it also concluded that "even 1 night of restricted sleep resulted in cognitive deficits in children; specifically, verbal creativity and abstract thinking/concert formation were affected" (Randazzo, et al., 1998, p. 866). The team of researchers believes their study suggests that the area most affected by sleep deprivation in children is executive function. Executive function skills allow the individual to "engage in creative, adaptive learning by initiating and regulating retrieval of knowledge from long-term memory, modifying the knowledge base, and mediating problem-solving" (Randazzo, et al., 1998, p. 866). Their findings also suggest that the area of the brain that is most affected by sleep deprivation is the frontal lobe, since that is where executive function occurs.
Long periods without sleep are shown to have an effect on cognitive functioning, but sleep deprivation can be adapted to if moderate restriction occurs on a nightly basis (Dinges, et al., 1997). A psychomotor vigilance task performed by 16 young adult subjects whose sleep was restricted to between 4 and 5 hours per night showed that lapses increased dramatically after two nights of sleep restriction. However, tests after nights 3, 4, 5, and 6 showed that the number of lapses did not increase. It was not until the seventh night of sleep restriction that the number of lapses increased again. This suggests that cognitive functioning is adapted to the amount of sleep a person normally receives (Dinges, et al., 1997, p. 271).
Sleep deprivation has also been shown to increase reaction time as demonstrated by a visual vigilance task (Corsi-Cabrera, Arce, Río-Portilla, Pérez-Garci, & Guevara, 1999). Through forty hours of total sleep deprivation, eight adult males were evaluated in their reaction time in a visual vigilance task every two hours. The vigilance task consisted of 150 stimuli on a computer screen. Subjects were asked to hit the "Enter" key when the target stimuli, a square with a missing corner, was presented. The subjects were evaluated before the period of sleep deprivation to obtain the control reaction times. This task showed a steady increase of reaction time over the 40 hours of total sleep deprivation. At the beginning of the 40-hour period, average reaction time of the subjects was approximately 360 milliseconds. After the final test and 40 hours of not sleeping, reaction time had increased to over 400 milliseconds (Corsi-Cabrera, et al., 1999). "These results suggest that deterioration of alertness and performance during sleep loss are due to changes in fundamental neurophysiologic mechanisms" (Corsi-Cabrera, et al., 1999, p. 181).
The Combined Effects of Alcohol Intoxication and Sleep Deprivation
In an article by Richard C. Schwing, it was shown that there is a high correlation between the risk of automobile accidents, alcohol consumption, and driver fatigue, depending on the time of day and day of the week. Risk of automobile accidents is increased on weekends, which researchers showed is when the most alcohol is consumed (Schwing, 1989-90). Risk is also highest from 10:00 p.m. to 4:00 am, when driver fatigue is greatest (Schwing, 278).
Two reaction time studies measured reaction times of visual and auditory tasks in subjects who were alcohol intoxicated and/or sleep deprived. In separate conditions, both sleep deprivation and alcohol intoxication caused poor performance on reaction time tasks (Smith, Sinha, & Williams, 1990). When the two treatments were combined, a blood alcohol content (BAC) of 0.05 and sleep deprivation produced a significant increase in reaction time. When subjects’ BAC was 0.08, sleep deprivation did not have a significant effect on reaction time. In a different study, subjects with a BAC of 0.08 showed a slight improvement in reaction time when also deprived of sleep (Smith et al, 1990). One reason the performance of the 0.08 BAC group was not affected may be that a higher level of alcohol impairment increased their own awareness of their intoxication and caused them to make a more serious effort to perform well. This is an interesting finding, but does necessarily show that sleep deprivation negates the effect of alcohol on reaction time, but that individuals can consciously compensate for the effects of alcohol to some extent.
However, another study by Peeke, Callaway, Jones, Stone, & Doyle (1980) does suggest that alcohol intoxication negates the effects of sleep deprivation. The study suggests that sleep deprivation causes increased anxiety, while alcohol intoxication leads to a decrease in anxiety level. The high anxiety level of subjects in a moderate alcohol group suggests that sleep deprivation counteracts the decreased anxiety normally induced by alcohol intoxication. Subjects are therefore more alert and complete a reaction time test more quickly than they normally would when intoxicated (Peeke et al., 1980).
These studies show that either sleep deprivation can negate the effects of high alcohol intoxication, or that the two conditions can have additive effects on cognitive performance. In general, when combined, moderate alcohol intoxication and sleep deprivation do cause some increase in reaction time.
Both sleep deprivation and alcohol consumption have detrimental effects on cognitive abilities. This finding leads us to the conclusions that college students in particular are at risk for lower scores on standardized tests and written exams due to poor sleep habits and excessive alcohol consumption. In addition, school aged children are at risk due to the early starting times of most secondary schools, which may prevent children/adolescents from getting adequate amounts of sleep. We recommend that 8am classes be abolished for these reasons, in all school settings. An additional problem was raised by Randazzo, who says, "As higher cognitive abilities seem essential to academic performance and success, a question that must be addressed is whether similar deficits result from more modest sleep restriction on 1 or more nights" (1998, p. 867). Due to our findings about the combination of sleep deprivation and alcohol consumption, we recommend that individuals take precautions when combining these two practices.
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