Sep 16, 2010
With World Alzheimer’s Day coming up (Sept 21st), it seemed important to make sense of the scientific study published this month that has triggered headlines claiming that “Doing puzzles could speed up dementia”, “Brain Exercise may worsen existing Alzheimer’s” and even explaining to readers “Why you shouldn’t play mentally stimulating games”.
What is the matter? Previous studies had shown it to be quite clear that people who lead a mentally or cognitively stimulating life also tend to:
a) benefit from improved thinking and overall cognitive functioning (delayed cognitive decline)
b) have reduced risks of manifesting Alzheimer’s disease symptoms
The new study, published in Neurology by Dr. Wilson from the Rush Alzheimer’s Disease Center followed more than 2,000 individuals 65 and over for 12 years. How often they participated in cognitive activities such as reading (book, magazines, newspapers), playing games (cards, crosswords, etc.), watching TV and going to a museum was first assessed. Each individual received a score on this cognitive activity scale. Six years later clinical evaluation was conducted to determine who was still highly functioning (all individuals started dementia free), who was suffering from mild cognitive impairment and who had Alzheimer Disease. The cognitive decline of individuals in these three categories (1,157 participants total) was then assessed over an average of 6 years.
This study is different from the previous ones showing that healthy people who are cognitively active have lower risks of developing dementia for one major reason: It assessed the fate of cognitively active individuals who have been diagnosed with dementia.
This stresses an important point: cognitive activity helps delay the emergence of dementia but doesn’t prevent it completely.
The results of the study confirmed that cognitive activity prior to dementia onset is protective: the annual rate of global cognitive decline for people who had no cognitive impairment was reduced by 52% for each additional point on the cognitive activity scale.
This means that individuals who had high cognitive activity scores showed delayed decline. Overall these individuals declined more slowly than individuals who were less cognitively active in the past. This also suggests that if these individuals were to develop dementia the onset of the disease would be delayed.
The other major result of the study is that once people who had high cognitive activity scores are diagnosed with Alzheimer they show compressed rates of decline.
This means that, after diagnosis, compared to less cognitively active people they will decline faster. Indeed the mean rate of cognitive decline per year for people in the Alzheimer group increased by 42% for each additional point on the cognitive activity scale.
Note that for individuals in the Mild Cognitive Impairment group (MCI is considered to be the very early stage of dementia), there was no effect of cognitive activity on decline.
Figure. This is a simple graphic representation of the results, shown on a time line. Individuals cognitively active before the study began (A) are represented by the top line. Individuals less cognitively active before the study began (B) are represented by the bottom line. The thick line represents the time that individuals live without impairment. The red mark represents Alzheimer’s diagnosis. The thin line represents the time that individuals live with dementia.
Are these results a big surprise? Does it mean that mentally stimulating activities are bad for the brain? No! As Dr. Wilson explained to us “Saying that cognitive activity worsens dementia is taking the results out of context.”
Here is a simple explanation of the results:
- Frequent cognitive activity stimulates different parts of the brain involved in memory and information processing. These parts of the brain become more resistant and more efficient. Cognitive reserve is built. If dementia is not present, normal cognitive decline is slower. If dementia is present, the brain can tolerate more dementia-related pathology and still function normally.
Consequence: In healthy people, more frequent cognitive activity is related to delayed and slower cognitive decline. Even if Alzheimer’s pathology is developing in the brain, the symptoms will not show until later. Dementia onset is thus postponed. Whether pathology is present in the brain or not, engaging in cognitive activity contributes to delay a decline that otherwise would occur.
- The brain can tolerate pathology only to a certain point. Cognitively active people who are diagnosed with dementia have reached a threshold of pathology at which it would be very hard to function normally. So when they are diagnosed with dementia cognitively active people have more pathology in the brain than less active people when they are diagnosed with dementia.
Consequence: For people who are now living with Alzheimer, having participated in cognitively engaging activities before the disease leads to compressed rates of decline. Given that they were diagnosed later compared to less active people, the pathology is more advanced in their brain and they will live less time with the disease.
We know that nothing can prevent Alzheimer’s Disease. However, as confirmed in this study, cognitive activity helps delay the onset of dementia. Since the decline experienced by cognitively active people is faster after diagnosis, does it make sense to say that cognitive exercise worsen dementia experience? In fact it seems the opposite. These individuals seem to spend less time experiencing the symptoms as these start showing later, when the pathology in the brain is already quite advanced. This is a huge benefit both from the point of view of the individual, the caregivers, and health costs overall.
As Dr. Wilson puts it the results can be explained in terms of “buying extra-time living as a highly functional individual and spending less time living with dementia.”
Dr. Daniel Goodman, a psychiatrist practicing in New York and Greenwich and an active participant in the LinkedIn SharpBrains group offers the following choice that summarize the situation very well: If you knew you had a progressive fatal condition (Alzheimer’s) that was definitely going to kill you in 10 years, then which of the following would you prefer:
1) Steady, gradual, progressive deterioration over 10 years, with death at that point (i.e. a slow rate of cognitive decline)
2) Symptom free life for 9 years, followed by rapid deterioration in year 10 ending in death (i.e. an eventual rapid cognitive decline, at the end stage of illness)
(Note that these numbers are purely hypothetical)
In sum this study suggests that engaging in cognitively stimulating activities before the age of 65 is related to:
- delayed cognitive decline and dementia onset
- if diagnosed, reduced number of years living with dementia
The absence of effect of prior cognitive activity in the group with mild cognitive impairment suggests that cognitive training or stimulation programs may need to start before any impairment develops to have an effect on rates of decline. However nothing in this study suggests that people with impairment should not engage in stimulating activities after diagnosis. Other studies have shown benefits for this population, such as better quality of life.
If we are trying to find ways to boost mental functions and delay decline, this study reinforces the idea that the earlier we start the better.
What kind of activity is the best to engaged in? In their studies, Dr. Wilson and his team deliberately chose activities that were “cognitive, that is activities involving processing and retaining information”. According to Dr. Wilson reading is such a prototypical activity. So you are exactly on the right track as you are reading this!
Reference: Wison, R. H., Barnes, L. L., Aggarwal, N. T., Boyle, P. A., Hebert, L. E., Mendes de Leon, C. F., & Evanc, D. A. (2010). Cognitive activity and the cognitive morbidity of Alzheimer disease. Neurology, 75, 990-996.