mental stimulation

Building Cognitive Reserve

  • Both age-related cognitive decline and brain damage like Alzheimer's can be countered by high levels of cognitive reserve.
  • Cognitive reserve is built throughout your life, but it's never too late to make a difference.
  • You can build cognitive reserve through active learning, intellectual work, being actively bi- or multi-lingual, or regularly engaging in mentally stimulating activities.
  • To maintain (or grow) cognitive abilities, it's important both to resist the brain's tendency to shrink (brain atrophy) , and to keep it flexible (neuroplasticity).
  • Brains shrink with disuse, and grow with use.
  • Brains stay plastic through change — in activities, in strategies, in perspective.

Brain autopsies have revealed that a significant number of people die with Alzheimer’s disease evident in their brain, although in life their cognition wasn’t obviously impaired. From this, the idea of a “cognitive reserve” has arisen — the idea that brains with a higher level of neuroplasticity can continue to work apparently normally in the presence of (sometimes quite extensive) brain damage.

A comprehensive review of the research into cognitive reserve, involving 29,000 individuals across 22 studies, concluded that complex mental activity across people’s lives almost halves the risk of dementia. Encouragingly, all the studies also agreed that it was never too late to build cognitive reserve.

As you might expect, the more years of education, the greater the cognitive reserve. But education isn’t the only means of building cognitive reserve. Basically, anything that’s mentally challenging is likely to build reserve. Research supports the following as builders of cognitive reserve:

  • Education
  • Occupational complexity
  • Bilingualism
  • Social engagement
  • Regular cognitive activities, such as reading, writing, attending lectures, doing word games or puzzles, playing games such as bridge or chess.

Will cognitive reserve stop me getting Alzheimer's?

This is not to say that the highly educated will never get Alzheimer’s! Obviously they do. In fact, once those with a high level of cognitive reserve begin to show signs of the disease, they are likely to decline faster. This isn’t surprising when you consider it, because the physical damage is so much greater by the time it becomes observable in behavior.

The point of having cognitive reserve is not to prevent Alzheimer’s, in the sense of “it’ll never happen”. When we talk about “preventing” Alzheimer’s, we're really talking about delaying it. The trick is to delay it so much that you're dead before it happens!

So, cognitive reserve is desirable because it protects you against the damage that may be occurring in your brain. If you’re lucky, it’ll protect you long enough to see you through your life.

Brains are plastic, all through life

Cognitive reserve is weighted toward the past — how much you’ve built up over your lifetime — but you shouldn’t ever forget that it’s an ongoing issue. If you stop all activities that reinforce neuroplasticity, your brain is likely to enter a downward spiral, with physical deterioration resulting from and feeding into a deterioration in your motor,sensory, and cognitive systems.

As the popular mantra has it: Use it or lose it.

It’s the opposite face of expertise. You know how top musicians continue to practice everyday. Although they have tens of thousands of hours of practice under their belt, although they have reached the highest level of performance, they cannot afford to stop. This isn’t simply about improving; this is about maintaining their level of expertise. As soon as you stop, your performance starts to deteriorate.

Of course, if an expert stops working in her area of expertise, she will still maintain abilities that are far and above ‘normal’. But the point is that you can’t maintain the same level of performance without working at it.

This is true at every level. If you haven’t ridden a bike for twenty years, you’re not going to leap on it and be as good as you were thirty years ago. If you haven’t spoken your native language in twenty years, you’re not going to suddenly get into a conversation in it with all the fluency you once had.

If you stop paying attention to taste, your appreciation of taste will dull (you’re not interested, why should your brain bother putting energy into it?). If you stop trying to distinguish what people are saying, you’ll become less able to distinguish words. If you stop walking outside the house, you’ll become less capable of movement. If you stop thinking, you’ll become less able to think.

If you just do the same things over and over again, giving your brain no reason to make or reinforce or prune connections, then it won’t bother doing any of that. Why should it? Brains are energy-hounds. If you don’t want to expend the energy making it work, it’s going to sit back and let itself shrink.

Maintaining cognitive abilities as you age begins with attitude

Recent evidence suggests that being cognitively active in middle and old age may help you develop new networks when existing networks start to fail. This is consistent with evidence that older adults who maintain their cognitive abilities do so by developing new strategies that involve different regions.

In other words, if you start to have difficulties with anything, your best strategy is not to give up, but to actively explore new ways of doing it.

So, we should be aiming for two things in preventing cognitive decline. The first is in ‘growing’ brain tissue: making new neurons, and new connections. This is to counteract the shrinkage (brain atrophy) that tends to occur with age.

The second concerns flexibility. Retaining the brain’s plasticity is a vital part of fighting cognitive decline, even more vital, perhaps, than retaining brain tissue. To keep this plasticity, we need to keep the brain changing.

Here’s a question we don’t yet know the answer to: how much age-related cognitive decline is down to people steadily experiencing fewer and fewer novel events, learning less, thinking fewer new thoughts?

But we do know it matters.

What activities help build cognitive reserve?

Research hasn't systematically compared different activities to find out which are better, but the general message is that any activity that engages your mind is good. But the degree of challenge does make a difference.

One small study involving older adults found that those who randomly put in a "high-challenge" group showed significantly more cognitive improvement and more efficient brain activity, compared to those assigned to the "low-challenge" group. Moreover, even among the high-challenge group, those who spent more time on the activities showed the greatest improvements.

The high-challenge spent at least 15 hours a week for 14 weeks learning progressively more difficult skills in digital photography, quilting, or a combination of both. The low-challenge group met to socialize and engage in activities related to subjects such as travel and cooking. A control group engaged in low-demand cognitive tasks such as listening to music, playing simple games, or watching classic movies.

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Achieving flow

I’ve recently had a couple of thoughts about flow — that mental state when you lose all sense of time and whatever you’re doing (work, sport, art, whatever) seems to flow with almost magical ease. I’ve mentioned flow a couple of times more or less in passing, but today I want to have a deeper look, because learning (and perhaps especially that rewiring I was talking about in my last post) is most easily achieved if we can achieve "flow" (also known as being ‘in the zone’).

Let’s start with some background.

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Mental stimulation

  • Growing evidence points to greater education, and mentally stimulating occupations and activities providing a cognitive reserve that enables people with developing Alzheimer's to function normally for longer.
  • There is also evidence that physical exercise and mental stimulation protect against the development of Alzheimer's, by preventing accumulation of beta-amyloid.
  • Physical exercise and mental stimulation also seem to help protect against age-related decline in cognitive function, possibly for similar reasons — by stimulating growth of new blood vessels and keeps existing vessels open and functional.
  • Mental stimulation is not only gained by more obvious intellectual pursuits, but also by activities as simple as talking to people or going to the theater.
  • Education also seems to help seniors retain their mental flexibility, enabling their brains to change strategies as age effects make different strategies more effective.

The evidence that diet, physical exercise, and mental stimulation all help prevent age-related cognitive decline and reduce the risk of mild cognitive impairment and Alzheimer’s, is now very convincing.

Studies of mice and (rather intriguingly) beagles, have provided evidence that ‘enriched’ environments — ones that provide opportunities for regular exercise and mental stimulation — reduce or prevent age-related cognitive decline, and reduce the risk of Alzheimer’s.

Studies of genetically engineered mice have also now shown how an enriched environment protects against Alzheimer’s — by preventing accumulation of beta-amyloid, and helping these peptides to be cleared away.

It’s been suggested that the benefits of physical and mental activity, which now seem undeniable, may simply be a matter of blood flow — that physical and mental activity stimulates growth of new blood vessels and keeps existing vessels open and functional.

These findings from animal studies have been supported by a number of human studies.

Physical exercise

A large, six-year study of adults aged 65 and older found that physical fitness and exercise were both associated with a significantly lower risk of dementia. Encouragingly, for those who are more frail, even modest amounts of exercise (such as walking 15 minutes a day) appear beneficial, and the more frail the person was, the more they benefited from regular exercise.

Education

Findings from two long-running studies of aging and cognition — the Nun Study and the Religious Orders Study — have revealed that formal education helps protect people from the effects of Alzheimer’s disease.

Note that I said “from the effects”. Education doesn’t prevent or delay the disease from developing, but it does provide a “cognitive reserve”, which allows the individual to function normally in the presence of brain abnormalities (the presence of an Alzheimer’s pathology is thus only evident when the brain is autopsied post-mortem).

As you would expect, the more years of education, the greater the cognitive reserve — the less effect the same number of plaques have on cognitive performance. It’s worth noting that the populations in these studies are all relatively well-educated — even the least educated had some college attendance — suggesting that the effect of education would be even more marked in the general population.

However, there is some evidence that, once the disease progresses to the point that it has noticeable effects, those effects progress faster. This is thought to be simply because the damage is so much greater by the time it becomes observable in behavior.

A general population study still in train has provided preliminary findings indicating that prevalence of mild cognitive impairment also is less common among those with more education.

Higher education also seems to help protect older adults from cognitive decline in general. One reason is clearly the cognitive reserve aspect, but an imaging study has also revealed another reason. In young adults performing memory tasks, more education was associated with less use of the frontal lobes and more use of the temporal lobes. For older adults doing the same tasks, more education was associated with less use of the temporal lobes and more use of the frontal lobes. Previous research has indicated frontal activity is greater in old adults, compared to young; this study therefore implies that this effect is related to the educational level in the older participants. The higher the education, the more likely the older adult is to recruit frontal regions, resulting in a better memory performance.

An earlier brain-scan study also provided support for the theory that the brain may change tactics as it ages, and that older people whose brain is more flexible can compensate for some aspects of memory decline.

Results from a large study of older adults from a biracial community in Chicago suggest that the benefits of education are not necessarily education per se. Although both education and occupation were associated with Alzheimer's risk in this study, their effects were substantially reduced when cognitive activity was taken into account.

In keeping with these findings, several smaller studies have also provided evidence that other aspects of mental activity are also associated with a reduced risk of cognitive decline and dementia.

Mental activity

People with Alzheimer's have been found to be more likely to have had less mentally stimulating careers, and those who are more active in high school and have higher IQ scores are apparently less likely to have mild memory and thinking problems and dementia as older adults.

A study of 469 people aged 75 and older found that those who participated at least twice weekly in reading, playing games (chess, checkers, backgammon or cards), playing musical instruments, and dancing were significantly less likely to develop dementia. Although the evidence on crossword puzzles was not quite statistically significant, those who did crossword puzzles four days a week had a much lower risk of dementia than those who did one puzzle a week.

Another study of 700 seniors found that more frequent participation in cognitively stimulating activities, such as reading books, newspapers or magazines, engaging in crosswords or card games, was significantly associated with a reduced risk of Alzheimer’s disease.

And more recently, a comprehensive review of the research into 'cognitive reserve', involving 29,000 individuals across 22 studies, concluded that complex mental activity across people’s lives almost halves the risk of dementia. Encouragingly, all the studies also agreed that it was never too late to build cognitive reserve.

Looking at the question of cognitive decline in general, a large-scale British study of people aged 35—55 found that those who scored highest on tests of cognitive ability made regular cultural visits to theatres, art galleries and stately homes. Other activities were also associated with higher cognitive ability (in order of importance):

  • reading, and listening to music
  • involvement in clubs and voluntary organisations
  • participation in courses and evening classes

Interestingly, the association was stronger among men.

Another study, of people aged 30—88, has found that those who were fluent in two languages rather than just one, were sharper mentally. This was true at all age groups, but bilinguals were also much less likely to suffer from the mental decline associated with old age. The participants were all middle class, and educated to degree level.

Social networks

There has been some evidence suggesting that simply talking helps keep your mind sharp at all ages, and that older people with more extensive social networks are less likely to suffer cognitive impairment.

More recently, a study has provided evidence that social networks also offer a 'cognitive reserve' that protects people from the ravages of Alzheimer's disease. To determine social network, participants were asked about the number of children they have and see monthly; about the number of relatives, excluding spouse and children, and friends to whom they feel close and with whom they felt at ease and could talk to about private matters and could call upon for help, and how many of these people they see monthly. Their social network was the number of these individuals seen at least once per month.

Post-mortem analysis revealed that, as the size of the social network increased, the same amount of Alzheimer’s pathology in the brain (i.e., extent of plaques and tangles) had less effect on cognitive test scores. In other words, for persons without much pathology, social network size had little effect on cognition. However, as the amount of pathology increased, the apparent protective effect on cognition also increased.

What you can do

The thought that your education, occupation, degree of physical fitness, and social involvedness, over the years, affects your risk of losing cognitive function, may relieve your anxieties or depress you. But if it depresses you, take heart from a recently-reported pilot study involving people aged 35–69. These people had some mild memory complaints but performed normally on tests. Nevertheless, in a mere two weeks, a program combining a brain healthy diet plan (5 small meals a day; diet rich in omega-3 fats, antioxidants and low-glycemic carbohydrates like whole grains), relaxation exercises, cardiovascular conditioning (daily walks), and mental exercise (such as crosswords and brain teasers) resulted in these participants' brain metabolism decreasing 5% in working memory regions, suggesting an increased efficiency. Compared to the control group, participants also performed better in verbal fluency, and felt as if they were performing better.

 

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Preventing Dementia: Mental stimulation

Stimulating activities

A 5-year study1 involving 488 people age 75 to 85 found that, for the 101 people who developed dementia, the greater the number of stimulating activities (reading, writing, doing crossword puzzles, playing board or card games, having group discussions, and playing music) they engaged in, the longer rapid memory loss was delayed. Similarly, a study2 involving 1321 randomly selected people aged 70 to 89, of whom 197 had mild cognitive impairment, has found that reading books, playing games, participating in computer activities or doing craft activities such as pottery or quilting was associated with a 30 to 50% decrease in the risk of developing memory loss compared to people who did not do those activities.

Moreover, two activities during middle age (50-65) were also significantly associated with a reduced chance of later memory loss: participation in social activities and reading magazines. The value of social activities is consistent with another, small, study3 that found that social networks, like education, offers a 'protective reserve' capacity that spares individuals the clinical manifestations of Alzheimer's disease. As the size of the social network increased, the same amount of Alzheimer’s pathology in the brain had less effect on cognitive test scores. For those without much pathology (plaques and tangles), social network size had little effect on cognition.

This supports another study4 involving 469 people aged 75 and older, that found that those who participated at least twice weekly in reading, playing games (chess, checkers, backgammon or cards), playing musical instruments, and dancing were significantly less likely to develop dementia. Although the evidence on crossword puzzles was not quite statistically significant, those who did crossword puzzles four days a week had a much lower risk of dementia than those who did one puzzle a week.

Similarly, a study5 of 700 seniors found that more frequent participation in cognitively stimulating activities, such as reading books, newspapers or magazines, engaging in crosswords or card games, was significantly associated with a reduced risk of Alzheimer’s disease. On average, compared with someone with the lowest activity level, the risk of disease was 47% lower for those whose frequency of activity was highest.

In the first comprehensive review6 of the research into 'cognitive reserve', which looks at the role of education, occupational complexity and mentally stimulating activities in preventing cognitive decline, researchers concluded that complex mental activity across people’s lives almost halves the risk of dementia. All the studies also agreed that it was never too late to build cognitive reserve. The review covered 29,000 individuals across 22 studies.

A review7 of research on the impact of cognitive training on the healthy elderly (not those with mild cognitive impairment or Alzheimer's disease), has found no evidence that structured cognitive intervention programs affects the progression of dementia in the healthy elderly population.

Post-mortem analysis of participants in a large, long-running study8 has provided more support for the idea that mental stimulation protects against Alzheimer’s. The study found a cognitively active person in old age was 2.6 times less likely to develop dementia and Alzheimer’s disease than a cognitively inactive person in old age. This association remained after controlling for past cognitive activity, lifetime socioeconomic status, and current social and physical activity. Frequent cognitive activity during old age was also associated with reduced risk of mild cognitive impairment.

Research involving genetically engineered mice9 has found that mice whose brains had lost a large number of neurons regained long-term memories and the ability to learn after their surroundings were enriched with toys and other sensory stimuli, pointing to the importance of maintaining cognitive stimulation as long as possible. Similarly, another mouse study10 found that short but repeated learning sessions can slow the development of those hallmarks of Alzheimer's, beta amyloid plaques and tau tangles. And another11 found that an enriched environment, with more opportunities to exercise, explore and interact with others, dramatically reduces levels of beta-amyloid peptides.

Education & iq

A study12 involving some 6,500 older Chicago residents being interviewed 3-yearly for up to 14 years (average 6.5 years), has found that while at the beginning of the study, those with more education had better memory and thinking skills than those with less education, education was not related to how rapidly these skills declined during the course of the study. The result suggests that the benefit of more education in reducing dementia risk results simply from the difference in level of cognitive function.

Another study13 has come out supporting the view that people with more education and more mentally demanding occupations may have protection against the memory loss that precedes Alzheimer's disease, providing more evidence for the idea of cognitive reserve. The 14-month study followed 242 people with Alzheimer's disease, 72 people with mild cognitive impairment, and 144 people with no memory problems.

Another study14 has come out confirming that people with more years of education begin to lose their memory later than those with less education, but decline faster once it begins. Researchers note that since the participants were born between 1894 and 1908, their life experiences and education may not represent that of people entering the study age range today.

A study15 of 312 New Yorkers aged 65 and older, who were diagnosed with Alzheimer's disease and monitored for over 5 years, found that overall mental agility declined faster for each additional year of education, particularly in the speed of thought processes and memory, and was independent of age, mental ability at diagnosis, or other factors likely to affect brain function, such as depression and vascular disease. It’s suggested this may reflect the greater ability of brains with a higher cognitive reserve to tolerate damage, meaning the damage is greater by the time it becomes observable in behavior.

The Nun Study16 found that nuns who completed 16 or more years of formal education or whose head circumference was in the upper two-thirds were four times less likely to be demented than those with both smaller head circumferences and lower education.

Post-mortem study17 of the brains of 130 participants in the Religious Orders Study found that the relationship between cognitive performance and the number of amyloid plaques in the brain changed with level of formal education. The more years education you had, the less effect the same number of plaques had on actual cognitive performance. It’s worth noting that this considerable difference was observed in a population where even the least educated had some college attendance; presumably the difference would be even more marked in the general population.

A long-running Finnish study18 has found that compared with people with five or less years of education, those with six to eight years had a 40% lower risk of developing dementia and those with nine or more years had an 80% lower risk. Generally speaking, people with low education levels seemed to lead unhealthier lifestyles, but the association remained after lifestyle choices and characteristics such as income, occupation, physical activity and smoking had been taken into account.

An analysis of high school records and yearbooks from the mid-1940s19, and interviews with some 400 of these graduates, now in their 70s, and their family members, has found that those who were more active in high school and who had higher IQ scores, were less likely to have mild memory and thinking problems and dementia as older adults.

An analysis20 of 184 people with dementia found that the mean age of onset of dementia symptoms in the 91 monolingual patients was 71.4 years, while for the 93 bilingual patients it was 75.5 years — a very significant difference.

A study21 of 122 people with Alzheimer's and 235 people without the disease found that people with Alzheimer's are more likely to have had less mentally stimulating careers than their peers who do not have Alzheimer's.

 

A study22 of 173 people from the Scottish Mental Survey of 1932 who have developed dementia has found that, compared to matched controls, those with vascular dementia were 40% more likely to have low IQ scores when they were children than the people who did not develop dementia. This difference was not true for those with Alzheimer's disease. The findings suggest that low childhood IQ may act as a risk factor for vascular dementia through vascular risks rather than the "cognitive reserve" theory. 

References: 

  1. Hall, C.B. et al. 2009. Cognitive activities delay onset of memory decline in persons who develop dementia. Neurology, 73, 356-361.
  2. Geda, Y.E. et al. 2009. Cognitive Activities Are Associated with Decreased Risk of Mild Cognitive Impairment: The Mayo Clinic Population-Based Study of Aging. Presented April 28 at the American Academy of Neurology's 61st Annual Meeting in Seattle.
  3. Bennett, D.A., Schneider,J.A., Tang,Y., Arnold,S.E. & Wilson,R.S. 2006. The effect of social networks on the relation between Alzheimer's disease pathology and level of cognitive function in old people: a longitudinal cohort study. Lancet Neurology,5, 406-412.
  4. Verghese, J., Lipton, R.B., Katz, M.J., Hall, C.B., Derby, C.A., Kuslansky, G., Ambrose, A.F., Sliwinski, M. & Buschke, H. 2003. Leisure Activities and the Risk of Dementia in the Elderly. New England Journal of Medicine, 348 (25), 2508-2516.
  5. Wilson, R.S., de Leon, C.F.M., Barnes, L.L., Schneider, J.S., Bienias, J.L., Evans, D.A. & Bennett, D.A. 2002. Participation in Cognitively Stimulating Activities and Risk of Incident Alzheimer Disease.
    JAMA, 287,742-748.
  6. Valenzuela, M.J. & Sachdev, P. 2006. Brain reserve and dementia: a systematic review. Psychological Medicine, In press
  7. Papp, K.V., Walsh, S.J. & Snyder, P.J. 2009. Immediate and delayed effects of cognitive interventions in healthy elderly: A review of current literature and future directions. Alzheimer's & Dementia, 5 (1), 50-60.
  8. Wilson, R.S., Scherr, P.A., Schneider, J.A., Tang, Y. & Bennett, D.A. 2007. The relation of cognitive activity to risk of developing Alzheimer’s disease. Neurology, published online ahead of print June 27.
  9. Fischer, A., Sananbenesi, F., Wang, X., Dobbin, M. & Tsai, L-H. 2007. Recovery of learning and memory is associated with chromatin remodelling. Nature, 447, 178-182.
  10. Billings, L.M., Green, K.N., McGaugh, J.L. & LaFerla, F.M. 2007. Learning Decreases Aß*56 and Tau Pathology and Ameliorates Behavioral Decline in 3xTg-AD Mice. Journal of Neuroscience, 27, 751-761.
  11. Lazarov, O.et al. 2005. Environmental Enrichment Reduces Aβ Levels and Amyloid Deposition in Transgenic Mice. Cell, 120(5), 701-713.
  12. Wilson, R.S., Hebert, L.E., Scherr, P.A., Barnes, L.L., de Leon, C.F.M. & Evans, D.A. 2009. Educational attainment and cognitive decline in old age. Neurology, 72, 460-465.
  13. Garibotto, V. et al. 2008. Education and occupation as proxies for reserve in aMCI converters and AD: FDG-PET evidence. Neurology, 71, 1342-1349.
  14. Hall, C.B., Derby, C., LeValley, A., Katz, M.J., Verghese, J. & Lipton, R.B. 2007. Education delays accelerated decline on a memory test in persons who develop dementia. Neurology, 69, 1657-1664.
  15. Scarmeas, N., Albert, S.M., Manly, J.J. & Stern, Y. 2006. Education and rates of cognitive decline in incident Alzheimer’s disease. Journal of Neurology Neurosurgery and Psychiatry, 77, 308-316.
  16. Mortimer, J.A., Snowdon, D.A. & Markesbery, W.R. 2003. Head Circumference, Education and Risk of Dementia: Findings from the Nun Study.Journal of Clinical and Experimental Neuropsychology, 25 (5), 671-679.
  17. Bennett, D.A., Wilson, R.S., Schneider, J.A., Evans, D.A., de Leon, M.C.F., Arnold, S.E., Barnes, L.L. & Bienias, J.L. 2003. Education modifies the relation of AD pathology to level of cognitive function in older persons. Neurology, 60, 1909-1915.
  18. Ngandu, T. et al. 2007. Education and dementia: What lies behind the association? Neurology, 69, 1442-1450.
  19. Fritsch, T., Smyth, K.A., McClendon, M.J., Ogrocki, P.K., Santillan, C., Larsen, J.D. & Strauss, M.E. 2005. Associations Between Dementia/Mild Cognitive Impairment and Cognitive Performance and Activity Levels in Youth. Journal of the American Geriatrics Society, 53(7), 1191.
  20. Bialystok, E., Craik, F.I.M. & Freedman, M. 2007. Bilingualism as a protection against the onset of symptoms of dementia. Neuropsychologia, 45 (2), 459-464./li>
  21. Smyth, K.A. et al. 2004. Worker functions and traits associated with occupations and the development of AD. Neurology, 63 (3), 498-503.
  22. McGurn, B., Deary, I.J. & Starr, J.M. 2008. Childhood cognitive ability and risk of late-onset Alzheimer and vascular dementia. Neurology, first published on June 25, 2008 as doi: doi:10.1212/01.wnl.0000319692.20283.10 .

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