"People who do puzzles and crosswords may stave off dementia longer,” according to BBC News. The website said that mentally stimulating activities may protect the brain from memory loss but also speed up mental decline once dementia takes hold.
The story is based on research that followed 1,157 elderly people to examine how mentally stimulating activity in old age affects the development of dementia. The results suggest that being mentally active slows down cognitive decline before the onset of dementia but leads to faster decline after dementia has set in. The authors suggest that mental activity may somehow allow the brain to initially tolerate the brain changes associated with Alzheimer’s, but that decline is swifter once brain changes reach a more advanced stage.
While it is interesting, the authors’ theory was not conclusively proven by this study and will need further testing. Mental activity is only one factor that may contribute to the risk of dementia, along with genetics, environment and education. The study did not specifically test brain-training games or puzzles, as some newspapers suggested.
Where did the story come from?
The study was carried out by researchers from Rush University Medical Center, Chicago, and was funded by the US National Institutes of Health.
The study was published in the peer-reviewed journal Neurology . It was widely reported by the media, whose coverage was generally fair but uncritical. Some newspapers focussed on the delays in dementia symptoms seen in people who were most mentally active, while others concentrated on the swifter mental decline they exhibited once dementia eventually began.
The Daily Mirror’s claim that “thinking too hard may actually damage the brain of some older people” is misleading. The study did not specifically test the impact of brain-training games or mental puzzles, both of which were mentioned in press coverage.
What kind of research was this?
The researchers point out that more frequent cognitive activity has been associated with a reduced risk of cognitive decline and symptoms of dementia. However, it has not been associated with any reduction in the development of brain lesions associated with the condition.
Given that greater mental activity appears to protect brain function but not biology, the researchers argue that if cognitive activity before dementia were truly protective, it would also be associated with more rapid decline after the onset of dementia. In this cohort study, they tested the hypothesis that by delaying the onset of dementia, greater cognitive activity would “compress” the illness once it began, with the condition progressing more rapidly over a shorter time.
What did the research involve?
The researchers recruited 1,157 people aged over 65 who did not have dementia at the time of enrolment. Participants were selected at random from a larger study looking at risk factors for dementia. At their initial interview, they were asked to rate how frequently they took part in seven activities in which information processing plays a central role. These included watching TV, reading, doing crosswords and visiting museums. Frequency was estimated using a five-point scale, ranging from every day (5 points) to once a year or less (1 point).
The researchers used these ratings to make an overall estimate of how often people participated in mentally stimulating activities. Participants were also given four validated cognitive performance tests to assess their cognitive abilities.
The participants were followed up for an average of 12 years. Every three years, different samples of the group underwent a comprehensive clinical evaluation, in which they were classified as having no cognitive impairment, mild cognitive impairment or Alzheimer’s disease. Participants underwent further brief cognitive testing at three-yearly intervals to assess cognitive function. (Three waves of clinical evaluation were included in this ongoing study. The fifth wave is still underway.)
The researchers used validated statistical methods to look at the possible associations between people’s levels of cognitive activity and their cognitive function and clinical outcomes.
What were the basic results?
Clinical evaluation over the course of the study found that 614 people had no cognitive impairment, 395 had mild cognitive impairment and 148 had Alzheimer’s disease. When the researchers analysed the data, they found that:
- In the group without cognitive impairment, the annual rate of cognitive decline was reduced by 52% for each additional point on the cognitive activity scale.
- In the group with mild cognitive impairment, the rate of cognitive decline was not associated with cognitive activity level.
- In the group with Alzheimer’s disease, the average annual rate of cognitive decline increased by 42% for each point of the cognitive activity scale.
Together, these results associate greater cognitive activity with slower decline in people without cognitive impairment and faster decline in those with Alzheimer’s disease.
How did the researchers interpret the results?
The researchers said their results suggest that cognitive activity enhances the brain’s ability to maintain relatively normal function despite neurological degeneration. This means that after the onset of dementia, the resulting decline is more rapid. They said that the benefit of delaying the initial appearance of cognitive impairment comes at the cost of a more rapid progression of dementia when it eventually arrives.
The researchers concluded that any mentally enriching interventions, such as puzzles or acting classes, may need to be started before the development of cognitive impairment, because many people with mild cognitive impairment already have substantial physiological signs of Alzheimer’s disease in the brain.
This study has some strengths, including the large number of patients followed and the long follow-up period. Furthermore, its clinical evaluations and assessments of cognitive function were based on validated measures. The participants also represent a broad spectrum of cognitive function, ranging from no impairment to dementia.
However, the study also has limitations.
- It did not make adjustments for other factors (called confounders) which might contribute to the development of Alzheiner’s. For example, certain educational, social and genetic factors may have differed between the groups, which were not accounted for in the researchers’ analyses.
- Importantly, the assessment of cognitive activity was based on a composite measure. Since only seven cognitive activities were assessed, they may not reflect people’s true levels of cognitive activity. The use of composite measures to assess cognitive function also means that specific deficits in memory, for example, were not tested for by themselves.
- Only two to three observations were recorded for each individual in the study. Therefore, when graphed, the rate of decline in cognitive function tended to appear as a straight line, whereas a more complex pattern may have been revealed if more than three data points had been available.
Overall, this study supports the authors’ theories about the development of Alzheimer’s. However, further research that adjusts for other known risk factors is needed before any practical recommendations can be made from the results.