Thursday July 17 2008
Does keeping your mind busy help prevent Alzheimer's?
“Maintaining a busy mind into old age by doing puzzles can help preserve the brain's memory centre and hold off degenerative diseases such as Alzheimer's”, reported The Daily Telegraph. It said that a study on 70 healthy volunteers over 60 years of age found keeping mentally active can “halve the rate at which the brain's memory centre deteriorates with age”. The Daily Mail also covered the story and suggested that simply reading or playing bingo could be as good for an ageing brain as learning a new language.
In this study, researchers assessed the mental activity of healthy, older individuals, and over the next three years looked at changes in the volume of their brains - in particular the hippocampus. Although those who had the lowest mental activity scores lost more than twice the volume than the average volunteer, all the volunteers showed a shrinkage in this part of the brain and the actual difference was quite small at 4.7%. In addition, the study was small and based on its findings alone, it is not possible to reach a reliable conclusion that increased mental activity through “cognitive training", like puzzles and crosswords, can prevent the shrinking of this part of the brain with age.
Where did the story come from?
Dr Michael J. Valenzuela from the School of Psychiatry at the University of New South Wales, and other colleagues from Sydney carried out the research. The study was funded by a program grant from the National Health and Medical Research Council of Australia. The study was published in the (peer-reviewed) open access medical journal published by the Public Library of Science: PLOS one.
What kind of scientific study was this?
In this cross-sectional descriptive study, the researchers assessed the mental activity of healthy, older individuals, and over the next three years looked at changes in the volume of their brains - in particular the hippocampus. The hippocampus is an area of the brain involved in short-term memory and navigation. It is also one of the first regions of the brain to suffer damage in Alzheimer’s disease.
The volunteers, healthy people over 60 years of age, were obtained from the control group of another study called the Sydney Stroke Study. In this study, 103 people were recruited from the local areas of two major teaching hospitals in Sydney between 1997-2000. They were required to undergo a series of mental tests and a medical, psychiatric and brain imaging examination. The study excluded any volunteers who had already been diagnosed with dementia, stroke, alcohol abuse, or other major neurological or psychiatric conditions that could have affected their thinking.
Although the participants had completed a variety of tests for the Sydney Stroke Study, this study only looked at a sub-group of the participants. In particular, the researchers were interested in those who completed a Lifetime of Experiences Questionnaire (LEQ) at the start of the study. The LEQ asks about mental activity levels in the areas of education, occupation, creative arts, reading, writing, socializing and day-to-day habits at different ages from young adulthood to late life. A higher total score is believed to indicate a higher level of complex mental activities across a lifespan.
Of the original 103 participants in the Sydney Stroke Study, 73 completed a LEQ and of this number 59 also had an MRI scan. After three years, 37 out of 70 individuals who could have a second evaluation agreed to it and had a repeat MRI scan. It is this sample of 37 people that the current study used. The MRI scan measured the volumes of the hippocampus, the whole brain and the density of white matter in the brain. The results were compared with regard to a variety of factors that the researchers had recorded at the first visit. Statistical tests were used to assess the strength of any link between the results of the questionnaire and the brain volumes on the MRI scans.
What were the results of the study?
At the three-year follow-up, higher scores on the LEQ were independently linked to higher hippocampal volumes. The high LEQ individuals experienced an average loss of 3.6% of hippocampal volume over the period, compared to low LEQ individuals who exhibited more than twice this volumetric loss (8.3)% in a multivariate analysis (a technique which analyses more than one statistical variable at a time). No parallel changes were found in measures of the whole brain volume or the density of the white matter in the brain.
What interpretations did the researchers draw from these results?
The researchers concluded that a “high level of complex mental activity across the lifespan” was linked to a reduced rate of hippocampal atrophy. They say that differences in intracranial volume, larger hippocampi in the beginning, high blood pressure, gender or low mood cannot explain the differences. They suggest that neuroprotection may be the mechanism behind the link between mental activity and lower rates of dementia observed in other studies.
What does the NHS Knowledge Service make of this study?
There are limitations to how this study and other similar cross-sectional studies of dementia can be interpreted. One limitation that the researchers themselves note is that the low LEQ group could have been affected by early dementia that had not yet been diagnosed. They said that they tried to address this concern in two ways;
- By controlling for brain volume at the beginning of the study in the multivariate analysis. They report that this will have reduced any association with signs of dementia that the participants may already have had.
- By analysing the data again using only the LEQ scores from the young adult and mid-life parts of the questionnaire. Although they report that the correlations were the same no results are given.
In addition, all participants showed a decline in hippocampal volumes over time and it is unclear how important the small change in volume shown in the adjusted multivariate analysis might be. It was not possible to carry out and compare cognitive tests in the participants who showed the fastest declines in hippocampal volumes.
Another feature that could affect the reliability of the conclusions include the fact that the questionnaires were only completed at the beginning of the study and it is not possible to know how much mental activity the participants had in the three years between MRI scans. This means that one interpretation of the results could be that the LEQ questionnaire was a good indicator of early declining memory and that this was confirmed by the changes in MRI-scan over the following three years. Although the LEQ is considered to be a valid measure of complex mental activity, precise details of how different features are assessed by the questionnaire or the cut off values used to differentiate between a high and a low score are not available in the journal article.
Finally, only 37 participants completed the LEQ questionnaire and received the repeat MRI scan at three years. This is a very small number to form reliable conclusions for an association between LEQ score and hippocampal volume.
In conclusion, it is not possible to say from this small study alone that increasing mental activity by “cognitive training” such as puzzles and crosswords can prevent the shrinking of this part of the brain with age.