Monday December 21 2009
Hangovers affect the ability to do tasks that require concentration
The Daily Mail reported, “a study has found that the severity of a hangover is affected by the colour of the alcohol being drunk, with darker drinks the worst offenders.”
This news story is based on a study of how alcohol affects sleep, and how a hangover affects performance of cognitive tasks. As part of the study, participants were asked about the severity of their hangover after consuming vodka or bourbon the evening before.
This relatively small study showed that either type of alcoholic beverage affected sleep and the participants’ ability to do cognitive tasks the next morning. Although participants reported worse hangovers from bourbon than from vodka, the study’s small size means that the findings may be due to chance. In addition, the study looked at only these two drinks, so it isn’t possible to generalise that darker drinks give worse hangovers.
Whatever the alcoholic drink, recommended daily maximums are two to three units for women and three to four units for men.
Where did the story come from?
The research was carried out by Dr Damaris Rohsenow and colleagues from Brown University, Boston University, and the University of Michigan Medical School in the US. The study was funded by the National Institute on Alcohol Abuse and Alcoholism. It was published in the (peer-reviewed) medical journal Alcoholism: Clinical and Experimental Research.
The BBC, Daily Telegraph and Daily Mail focused on the reported difference between the hangovers experienced with vodka compared to bourbon. This was just a small part of the study, which examined how cognitive abilities are affected by hangovers. The Daily Mail incorrectly reported that the research had also looked at white wine and red wine.
The newspapers also focused on the researchers’ speculation that the difference in reported hangovers may arise from a greater number of bi-products from the fermentation process in bourbon compared to vodka. However, this was not directly tested in the research, and it was overemphasised in the press.
What kind of research was this?
This was a randomised placebo controlled trial that investigated hangovers.
The researchers wanted to see whether having a hangover has an adverse effect on performance in cognitive tasks. They also wanted to see if the number of chemical by-products in drinks from their fermentation process have an effect. To this end, they compared vodka, which contains relatively few by-products, to bourbon, which has about 37 times more bi-products than vodka.
Although this is the best type of study to look at the short-term effects of alcohol, the study was relatively small. This increases the possibility that the results are due to chance. In addition, some of the measures of hangover (an experience that varies greatly between individuals) were subjective.
Also, drinking habits vary greatly. Although people with diagnosed drinking problems were excluded, there is still likely to be a large degree of variation within the population.
What did the research involve?
The researchers recruited 95 university students and recent graduates between 21 and 35 years old.
To be eligible for inclusion, participants had to have consumed more than five drinks on the same occasion at least once in the 30 days before the study. The participants were screened for alcohol-related problems, and anyone with a history of counselling or treatment was excluded, as were people with sleep disorders, and those on medication that could react with alcohol. All female participants had a pregnancy test.
The experiment was carried out over two evenings, which were a week apart. On one evening, the participants drank alcohol. On the other, they were given an alcohol-free placebo drink. In the 24-hour period before each of these evenings, the participants were required to abstain from alcohol, illicit drugs, sleep aids and caffeine.
Prior to the drinking experiments, all participants performed a series of cognitive tasks. They also underwent an initial overnight observation using polysomnography, which measures brain activity, eye movements and heart rate during sleep. This can give information about quality and type of sleep.
On each experiment day, participants were all given the same meal at 4pm, then assigned to receive either vodka or bourbon mixed with caffeine-free cola, or an alcohol-free cola. Between 8.30pm and 10pm, they consumed the drinks, performed cognitive tasks and had their breath alcohol content measured. Their alcohol dose was adjusted to ensure that they were likely to get a hangover.
At 11pm they were allowed to sleep, while polysomnogram recordings were made, through to 7am, when they had a breathalyser test. They were also asked to describe their hangover in terms of their symptoms, and how incapacitated they felt. At 8am, they performed more cognitive tasks. The participants were also asked to report how well they thought they had slept and performed in the tasks. As an additional measure of how impaired they felt, participants were asked how much they thought their driving ability was affected, and their likelihood of being able to drive at that moment.
What were the basic results?
Participants reported a worse hangover from bourbon than vodka. They also reported worse sleep after alcohol, but no difference between the two alcoholic drinks. Those that had drunk alcohol the night before had worse performances on cognitive tests that required sustained attention, quick reaction times or speed.
With alcohol, sleep efficiency and the amount of time in REM sleep decreased, while the amount of time that participants stayed awake after waking up increased.
The researchers found an association between the severity of self-reported hangovers and disturbed sleep. People who reported a worse hangover tended to do worse on cognitive tasks. However, no association was found between sleep disturbance and cognitive performance.
Most participants did not think that their driving ability was impaired in the morning. However, they said they would be less willing to drive the morning after alcohol than after placebo.
How did the researchers interpret the results?
The researchers concluded that alcohol affects complex cognitive abilities the next morning, and this has implications for driving and potentially hazardous occupations. Vodka and bourbon may result in different severities of hangover, but they have the same effect on cognitive abilities the next morning. Analysis showed that the sleep-disrupting effects of alcohol did not account for the impaired performance.
The researchers suggest that as hangover symptoms correlate with impaired performance, these symptoms may be contributing to the impairment.
This research investigated how performance of cognitive tasks is affected by a hangover, how this relates to the quality of sleep achieved after drinking, and whether different alcoholic drinks have different effects on hangover.
This study was small, and required subjective reporting of hangover intensity, which may vary between individuals. The researchers also highlight the following limitations to their study:
- The study only involved young adults. It is possible that the effects would differ among older adults with longer drinking histories and possibly more behavioural tolerance.
- People with probable alcohol dependence were excluded, yet such people are more likely to drink to intoxication on a regular basis.
- The participants’ hangovers were induced at a level according to the minimum target breath alcohol content. Higher doses would produce more severe hangovers, probably more next-day impairment, and more sleep disruption.
- As the participants were given a large quantity of alcohol, most people could tell which type of beverage they received. This meant that the study was not blind, which possibly affected how people reported their symptoms.
- The researchers speculated that hangover severity may have been influenced by a greater amount of bi-products from fermentation in bourbon compared to vodka. However, this is only a theory. As they only compared two alcoholic beverages, it is not possible to say what caused the reported difference in hangover severity between the two drinks.
Although the results from this study suggest that bourbon induces worse hangovers than vodka, the findings are based on subjective measurements in a relatively small group of people. This would therefore need to be established through further research. In addition, the research looked only at these two drinks. The extrapolation that darker drinks therefore result in worse hangovers than lighter drinks is not supported. The theory that the severity of hangovers is associated to the amount of bi-products in the drinks remains a theory.
What the study does show is that, regardless of which of these spirits is consumed, hangovers affect the ability to do tasks that require concentration and attention.