Monday May 11 2009
Heavier drinkers performed poorly in memory tests
“Alcohol ‘could cause one in four cases of dementia’,” the Daily Mail has claimed, saying that doctors have warned that an “epidemic of brain damage” may arise from Britons’ increasing thirst for alcohol. The newspaper reports that young drinkers may go on to experience memory problems while still in their 40s.
The small medical journal article behind these reports suggests that dependent drinkers have greater difficulty recalling specific autobiographical memories compared to non-dependent drinkers. The study was not set up to determine whether this memory deficit was directly linked to drinking alcohol or whether it arose from mental health problems that may be associated with substance dependency.
Other research reported in some newspapers also specifically considers alcohol-related brain disorders including potentially fatal Korsakoff syndrome, which is linked to alcohol abuse. The factors surrounding alcohol-related brain damage are complex, and further studies are needed to assess what impact different treatments may have for dependent drinkers. As the authors highlight, research in this area may also change the way dementia services operate in the future.
Where did the story come from?
The news report is based on a small study reported in a letter from Dr Jane Marshall and colleagues from the East London NHS Foundation Trust, the University of London and University College London (UCL). The letter was published in the peer-reviewed medical journal Alcohol & Alcoholism. The study was supported with grants from UCL Graduate School and UCL Clinical Health Psychology and the Tregaskis Bequest, University of London.
Another publication in the same journal by Dr Michael Kopelman and colleagues from the Institute of Psychiatry, UCL and the Maudsley discusses one category of alcohol-related brain damage, the Wernicke-Korsakoff syndrome.
What kind of scientific study was this?
This was a letter discussing a study on the ability of alcohol-dependent individuals to recall memories, briefly referring to research methods.
The study mentioned was a controlled case-series study where 26 detoxified drinkers under treatment were recruited, along with 29 non-dependent drinkers sourced from the community.
Both groups underwent a battery of tests to assess memory function, including an estimate of pre-morbid intelligence, a measure of current symptoms of depression and an Autobiographical Memory Test (AMT). The memory test presents a series of cues to which participants are asked to recall a personal memory that is specific to that cue, such as the first time they experienced a particular event.
The drinkers in this study had not consumed a drink for 16 days on average, ranging from one to 365 days. The drinkers scored an average of 35 on the Severity of Alcohol Dependence Questionnaire, meaning that they had severe alcohol dependence. The researchers were interested in whether detoxified dependent drinkers and non-dependent drinkers differed in their ability to recall autobiographical memories. Each participant was questioned 18 times about their memories.
A separate piece of research on Wernicke-Korsakoff syndrome has also been discussed in some newspaper reports. The brain condition is found in alcoholics, and is the result of a deficiency of the vitamin, thiamine. The treatable condition is known to affect memory.
What were the results of the study?
The study found that dependent drinkers had fewer specific autobiographical memories than non-dependent drinkers, with an average of 9.15 compared to 13.72 for non-dependent drinkers. This difference was statistically significant.
Dependent drinkers could recall a specific memory for around 51% of the cues, while non-dependent drinkers recalled a memory for 76% of cues. Dependent drinkers took longer to recall specific memories (18.89 versus 13.69 seconds) and had higher depression scores.
What interpretations did the researchers draw from these results?
The researchers conclude that detoxified dependent drinkers show a reduced memory specificity similar to that seen in other clinical populations, such as people with depression or trauma.
What does the NHS Knowledge Service make of this study?
Dr Marshall and colleagues have raised the main weaknesses associated with their study:
- This was a small study, including only 55 people, only 26 of whom were detoxified dependent drinkers currently under treatment.
- The person who assessed memory test responses knew which of the groups each participant came from.
- The researchers note that many dependent drinkers also have mental health problems, which may affect their ability to recall memories. Apart from depression these were not assessed, and could have confounded the relationships between drinking and memory recall.
Overall, this study suggests that alcohol does have an effect on memory recall. Whether this is linked to other mental health problems common in dependent drinkers remains unclear from this research, and should be assessed further. The researchers also call for further investigation of the specificity of autobiographical memory in problem drinkers, in order to determine the effects that different treatments may have on memory changes.
As highlighted by the second piece by Kopelman and colleagues, alcohol-related dementia accounts for 10-24% of all cases of dementia, and even in these cases it is not well understood. Regardless of the specific causes Wernicke-Korsakoff syndrome is one category of alcohol-related brain damage that can be fatal. It can also cause survivors to need long-term institutionalisation.