Abstract: Long-term alcohol abuse is associated with poorer cognitive performance. However, the associations between light and moderate drinking and cognitive performance are less clear. We assessed this association via cross-sectional and longitudinal analyses in a sample of 702 Dutch students. At baseline, alcohol consumption was assessed using questionnaires and ecological momentary assessment (EMA) across four weeks (‘Wave 1’). Subsequently, cognitive performance, including memory, planning, and reasoning, was assessed at home using six standard cognition tests presented through an online platform. A year later, 436 students completed the four weeks of EMA and online cognitive testing (‘Wave 2’). In both waves, there was no association between alcohol consumption and cognitive performance. Further, alcohol consumption during Wave 1 was not related to cognitive performance at Wave 2. In addition, EMA-data-based drinking patterns, which varied widely between persons but were relatively consistent over time within persons, were also not associated with cognitive performance. Post-hoc analyses of cognitive performance revealed higher within-person variance scores (from Wave 1 to Wave 2) than between-person variance scores (both Wave 1 and Wave 2). In conclusion, no association was observed between alcohol consumption and cognitive performance in a large Dutch student sample. However, the online cognitive tests performed at home may not have been sensitive enough to pick up differences in cognitive performance associated with alcohol consumption.
Keywords: young adult; alcohol consumption; cognitive performance
4. Discussion
We hypothesized that light to moderate drinkers would obtain similar cognitive task scores as
compared to abstainers, whereas heavy drinkers would obtain lower cognitive task scores. While the
first part of our hypothesis was retained, we did not find lower cognitive task scores for heavy drinkers.
In this study, we did not find any consistent association between alcohol consumption and cognitive
performance in a large population-based sample of young Dutch adults. This observation was made
both cross-sectionally as well as longitudinally after a one-year follow-up. These null findings were
observed for both the average amount of alcohol consumed as well as for the various drinking patterns.
However, the results of this study should be interpreted with caution, because the null findings of this
study have to be viewed in light of the high variance of the cognition scores.
The strengths of this study are the use of a large and homogeneous group of young adults: all
students of similar age and similar level of education. This is relevant because cognitive performance
largely depends on age and educational level. The group, however, spanned a large range of alcohol
consumption and included various drinking patterns. Both the cross-sectional and longitudinal
analysis used validated and well-recognized cognition tests. We selected these cognitive tests, since we
considered them to provide a somewhat better indicator for day-to-day functioning and brain health
as compared to functional MRI images showing changing patterns of blood circulation [14,15].
EMA may be a suitable methodology for alcohol consumption evaluation. EMA encompasses
the brief but intensive repeated assessment of people’s thoughts, feelings, and behaviors in their
real-world settings. The ecological validity of EMA data is considered high [19]. EMA reduces
retrospective bias when assessing alcohol consumption, as suggested by higher consumptions as
compared to consumptions recorded by regular questionnaire. EMA also has a low cognitive bias
due to direct retrieval [33]. Furthermore, the repetitive data collection allowed the study of drinking
patterns in addition to commonly reported average consumption levels. This is relevant since
alcohol-drinking pattern may be an important determinant for the harmful effects of drinking, such as
binge drinking [11,12,20].
Population surveys using questionnaires typically report underestimates of alcohol consumption
of approximately 40–50%. Researchers adjust alcohol survey data to weight estimates such that
they match alcohol sales or alcohol tax data. The current study suggests that underestimation of
alcohol consumption in this population exists, but to a lesser extent than assumed in population
surveys. EMA has been recognized as an alternative for assessing alcohol consumption in the natural
environment [34].
Previous studies found inconsistent results on the relation between alcohol consumption and
cognitive performance. The majority of studies indicate that long-term heavy drinking has strong
negative associations with diseases of the brain such as dementia [35]. Many short-term studies
indicate cognitive impairment in heavy binge drinkers as compared to nondrinking controls [8–13].
The outcome of comparing two groups differing in drinking habits, however, may depend on the
selection criteria and may potentially be hampered by confounding. Excessive heavy drinking is
usually accompanied by impulsive behaviors, risk-seeking behavior [36], and other traits [16] that may
confound the association between alcohol consumption and cognitive performance. Some authors
suggest that impaired cognitive performance may partly predict excessive alcohol consumption,
whereas excessive alcohol consumption does not always predict impaired cognitive functioning [37].
Contrary to the differences in cognitive performance between heavy binge-drinkers and
nonbinge-drinking controls, long-term moderate drinking has been associated with a reduced risk
of dementia and a reduced risk of cognitive decline. Reviews of prospective studies showed that
moderately drinking elderly have a decreased risk of dementia and cognitive decline [38,39]. Thus,
after a very long follow-up, moderately drinking persons may be expected to show a less severe decline
in cognitive performance as compared to those that drink excessively and abstainers. This suggests
that there may be a J-shaped association between alcohol consumption and dementia and cognition, as
has been described for cardiovascular diseases [40]. The risk reduction for dementia and age-related
cognitive decline observed in the elderly may occur through a mechanism related to cardiovascular
disease risk factors, whereas the cognitive impairment observed in young binge-drinking adults may
occur through a mechanism related to neurotoxicity.
Our results correspond with those reported previously by Boelema et al. [18]. The null findings
regarding the association between alcohol consumption and cognitive performance in that study were
interpreted as being methodological in nature; the tests used may not have been sensitive enough
to detect a potential cognitive performance reduction as a consequence of alcohol consumption. We
also used conventional standard tests that are routinely used for cognitive performance evaluations.
However, some aspects of our testing differed. Firstly, the tests were performed in an ‘at home situation’
as opposed to ‘at a testing facility’, which may have affected the results in various ways. For some
individuals, performing cognitive tests in an environment that they are familiar with may positively
influence performance. For others, the at home environment may have provided more distraction, or
the lack of experimental control and the fact that no experimenter was present may have reduced focus
and motivation, negatively affecting performance. All these factors may have affected test results and
might explain the high within-person variability. Secondly, cognitive tests employed in the present
study did not allow evaluation of aspects like reaction time, which may have contributed to a less
complete test result.
The cognition tests did seem to detect differences, since small significant differences were observed
for education level. It is important, however, to extend these studies to enable detection of small
differences in cognitive performance that may be induced by light and moderate alcohol drinking.
Significant differences in cognition tests may be detected by decreasing the variability in the cognition
test outcomes.
Although the study was set up with a group of students to obtain a high degree of homogeneity,
this also has its limitations. The results obtained in this group cannot be generalized to the general
population nor to specific other groups like persons with a low socioeconomic status. Specific groups
may respond differently to alcohol consumption and may have more difficulty in adapting their
drinking pattern whenever needed. In general, it has been extensively described that adolescents are
less sensitive to the negative effects of alcohol, including cues that influence self-regulation of intake,
but are more sensitive to positive effects, which may serve to reinforce or promote excessive intake [41].
This response to alcohol may promote the development of alcohol use disorders, a development
university students may be less vulnerable to as compared to other groups of adolescents [7].
Our study design, however, had several limitations that warrant consideration. The null findings
of this study have to be viewed in light of the high variance of the cognition scores. Whereas in
the ‘real-life’ study, the within-person variability was higher than the between-person variability, in
the laboratory study, the within-person variability was lower than the between-person variability.
This suggests that the use of cognition tests in a ‘real-life’ setting may not have been suitable or
sufficiently sensitive to detect a possible reduction in cognitive performance in association with alcohol
consumption. Some of the tasks were, however, sensitive to education level, as university students
outperformed polytechnic students, which would be expected as the former is a higher level of
education. Furthermore, it is expected that the cognition tests used in this study might have been
adequate to detect (possible) small differences in cognitive performance when used in a laboratory
setting, provided a sufficiently large participants population.
In the present study, follow-up time was only one year. It would have been interesting to show
in the same cohort that students who keep on drinking in a hazardous way will show cognitive
impairment after many years. Boelema et al. [18], however, did report on cognitive performance after
a four-year follow-up yet did not find indications for cognitive impairment in adolescent drinkers,
including heavy drinkers.
In conclusion, it is important to build on this study by reducing variance in online cognitive
testing or by testing in a laboratory setting to better assess the association between light and moderate
alcohol drinking and cognitive performance. In the present study, variance in cognitive performance
was too large to detect an association, if any, between alcohol consumption and cognitive performance.
Future studies should carefully consider both the context in which cognition is assessed as well as the
type of tasks that are used.
We hypothesized that light to moderate drinkers would obtain similar cognitive task scores as
compared to abstainers, whereas heavy drinkers would obtain lower cognitive task scores. While the
first part of our hypothesis was retained, we did not find lower cognitive task scores for heavy drinkers.
In this study, we did not find any consistent association between alcohol consumption and cognitive
performance in a large population-based sample of young Dutch adults. This observation was made
both cross-sectionally as well as longitudinally after a one-year follow-up. These null findings were
observed for both the average amount of alcohol consumed as well as for the various drinking patterns.
However, the results of this study should be interpreted with caution, because the null findings of this
study have to be viewed in light of the high variance of the cognition scores.
The strengths of this study are the use of a large and homogeneous group of young adults: all
students of similar age and similar level of education. This is relevant because cognitive performance
largely depends on age and educational level. The group, however, spanned a large range of alcohol
consumption and included various drinking patterns. Both the cross-sectional and longitudinal
analysis used validated and well-recognized cognition tests. We selected these cognitive tests, since we
considered them to provide a somewhat better indicator for day-to-day functioning and brain health
as compared to functional MRI images showing changing patterns of blood circulation [14,15].
EMA may be a suitable methodology for alcohol consumption evaluation. EMA encompasses
the brief but intensive repeated assessment of people’s thoughts, feelings, and behaviors in their
real-world settings. The ecological validity of EMA data is considered high [19]. EMA reduces
retrospective bias when assessing alcohol consumption, as suggested by higher consumptions as
compared to consumptions recorded by regular questionnaire. EMA also has a low cognitive bias
due to direct retrieval [33]. Furthermore, the repetitive data collection allowed the study of drinking
patterns in addition to commonly reported average consumption levels. This is relevant since
alcohol-drinking pattern may be an important determinant for the harmful effects of drinking, such as
binge drinking [11,12,20].
Population surveys using questionnaires typically report underestimates of alcohol consumption
of approximately 40–50%. Researchers adjust alcohol survey data to weight estimates such that
they match alcohol sales or alcohol tax data. The current study suggests that underestimation of
alcohol consumption in this population exists, but to a lesser extent than assumed in population
surveys. EMA has been recognized as an alternative for assessing alcohol consumption in the natural
environment [34].
Previous studies found inconsistent results on the relation between alcohol consumption and
cognitive performance. The majority of studies indicate that long-term heavy drinking has strong
negative associations with diseases of the brain such as dementia [35]. Many short-term studies
indicate cognitive impairment in heavy binge drinkers as compared to nondrinking controls [8–13].
The outcome of comparing two groups differing in drinking habits, however, may depend on the
selection criteria and may potentially be hampered by confounding. Excessive heavy drinking is
usually accompanied by impulsive behaviors, risk-seeking behavior [36], and other traits [16] that may
confound the association between alcohol consumption and cognitive performance. Some authors
suggest that impaired cognitive performance may partly predict excessive alcohol consumption,
whereas excessive alcohol consumption does not always predict impaired cognitive functioning [37].
Contrary to the differences in cognitive performance between heavy binge-drinkers and
nonbinge-drinking controls, long-term moderate drinking has been associated with a reduced risk
of dementia and a reduced risk of cognitive decline. Reviews of prospective studies showed that
moderately drinking elderly have a decreased risk of dementia and cognitive decline [38,39]. Thus,
after a very long follow-up, moderately drinking persons may be expected to show a less severe decline
in cognitive performance as compared to those that drink excessively and abstainers. This suggests
that there may be a J-shaped association between alcohol consumption and dementia and cognition, as
has been described for cardiovascular diseases [40]. The risk reduction for dementia and age-related
cognitive decline observed in the elderly may occur through a mechanism related to cardiovascular
disease risk factors, whereas the cognitive impairment observed in young binge-drinking adults may
occur through a mechanism related to neurotoxicity.
Our results correspond with those reported previously by Boelema et al. [18]. The null findings
regarding the association between alcohol consumption and cognitive performance in that study were
interpreted as being methodological in nature; the tests used may not have been sensitive enough
to detect a potential cognitive performance reduction as a consequence of alcohol consumption. We
also used conventional standard tests that are routinely used for cognitive performance evaluations.
However, some aspects of our testing differed. Firstly, the tests were performed in an ‘at home situation’
as opposed to ‘at a testing facility’, which may have affected the results in various ways. For some
individuals, performing cognitive tests in an environment that they are familiar with may positively
influence performance. For others, the at home environment may have provided more distraction, or
the lack of experimental control and the fact that no experimenter was present may have reduced focus
and motivation, negatively affecting performance. All these factors may have affected test results and
might explain the high within-person variability. Secondly, cognitive tests employed in the present
study did not allow evaluation of aspects like reaction time, which may have contributed to a less
complete test result.
The cognition tests did seem to detect differences, since small significant differences were observed
for education level. It is important, however, to extend these studies to enable detection of small
differences in cognitive performance that may be induced by light and moderate alcohol drinking.
Significant differences in cognition tests may be detected by decreasing the variability in the cognition
test outcomes.
Although the study was set up with a group of students to obtain a high degree of homogeneity,
this also has its limitations. The results obtained in this group cannot be generalized to the general
population nor to specific other groups like persons with a low socioeconomic status. Specific groups
may respond differently to alcohol consumption and may have more difficulty in adapting their
drinking pattern whenever needed. In general, it has been extensively described that adolescents are
less sensitive to the negative effects of alcohol, including cues that influence self-regulation of intake,
but are more sensitive to positive effects, which may serve to reinforce or promote excessive intake [41].
This response to alcohol may promote the development of alcohol use disorders, a development
university students may be less vulnerable to as compared to other groups of adolescents [7].
Our study design, however, had several limitations that warrant consideration. The null findings
of this study have to be viewed in light of the high variance of the cognition scores. Whereas in
the ‘real-life’ study, the within-person variability was higher than the between-person variability, in
the laboratory study, the within-person variability was lower than the between-person variability.
This suggests that the use of cognition tests in a ‘real-life’ setting may not have been suitable or
sufficiently sensitive to detect a possible reduction in cognitive performance in association with alcohol
consumption. Some of the tasks were, however, sensitive to education level, as university students
outperformed polytechnic students, which would be expected as the former is a higher level of
education. Furthermore, it is expected that the cognition tests used in this study might have been
adequate to detect (possible) small differences in cognitive performance when used in a laboratory
setting, provided a sufficiently large participants population.
In the present study, follow-up time was only one year. It would have been interesting to show
in the same cohort that students who keep on drinking in a hazardous way will show cognitive
impairment after many years. Boelema et al. [18], however, did report on cognitive performance after
a four-year follow-up yet did not find indications for cognitive impairment in adolescent drinkers,
including heavy drinkers.
In conclusion, it is important to build on this study by reducing variance in online cognitive
testing or by testing in a laboratory setting to better assess the association between light and moderate
alcohol drinking and cognitive performance. In the present study, variance in cognitive performance
was too large to detect an association, if any, between alcohol consumption and cognitive performance.
Future studies should carefully consider both the context in which cognition is assessed as well as the
type of tasks that are used.
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