Aging

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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Benefits of vitamins & minerals for cognition

  • Iron is important at all ages, and it seems clear now that iron deficiency can affect cognition long before anemia is diagnosed. However, too much iron may also increase Alzheimer's risk, so you need to steer a middle road.
  • Magnesium and zinc also seem to be important minerals for cognition, and zinc deficiency has been linked to Alzheimer's.
  • B vitamins, especially B12 and folate, are important to fight age-related cognitive impairment and Alzheimer's.
  • Vitamins C, D, and E, are probably also important in this fight.
  • Interactions need to be taken into consideration. Zinc may impact iron absorption; vitamin C may not be well absorbed if iron is not bound; the vitamins are more effective if omega-3 levels are high.

Let me start by saying that if you're healthy and are eating a good balanced diet, there should be no need for you to take supplements. I also want to emphasize that the best way of meeting your body's needs for certain vitamins and minerals is to get them from food. In some cases, for one reason or another, this may not be possible. For example, as a (mostly) vegan, I take iron and B12 supplements, to make up for these deficiencies in my diet. Elderly adults with small appetites may also find it hard to get all the nutrients they need from their diet.

What nutrients are important for brain health and cognition?

Minerals

Number one mineral for cognition, that goes right across the age groups, is iron. A number of studies have found that iron deficiency in children and adolescents is associated with lower scores of cognitive tests, and indeed, it may be that iron deficiency during infancy has long lasting effects on cognition. The effects on adults have been less studied, but there is some evidence that iron deficiency may be linked to poorer attention. What's worth noting is that the levels at which iron is "deficient" may be overstated. It now seems that negative effects occur long before a person is officially diagnosed with anemia.

Other minerals that may impact learning and memory are magnesium and zinc, although evidence is limited thus far. Magnesium deficits are common in industrialized countries, and increase with age. Vegetarians, adolescents, and older adults, are particularly at risk of zinc deficiency. An analysis of Alzheimer's has revealed that one type of the disease, which is found most commonly at a younger age (50- to early 70s) and typically shows itself first in language and number difficulties, is associated with a significant zinc deficiency.

Good sources of magnesium are dark green leafy vegetables, some nuts (especially almonds and cashews), beans, seeds and whole unrefined grains (especially buckwheat). Red meats, fish and grains are good sources of zinc.

Do bear in mind that it is not a case of "if some is good, more is better"! Having too much is not a good idea either; this is another reason why getting your vitamins and minerals from food rather than supplements is a good idea. Too much iron, in particular, has been linked to an increased risk of Alzheimer's. It has been argued that many neurodegenerative diseases are partly caused by poorly bound iron, and it is vital to consume nutrients which bind iron, such as brightly-colored fruits (especially purple) and vegetables — but not, perhaps, green tea, which does bind iron, but taking them at the same time seems to cancel out each other's benefits!

Just to complicate the matter further, there is evidence that zinc inhibits iron absorption. These complications suggest there is something in the idea that you need to consider food combinations.

Vitamins

Vitamins B, C, D, and E all seem to be important for cognition, mainly in relation to prenatal development and prevention of Alzheimer's and age-related cognitive impairment. A long-running study of older adults found that those with diets high in omega 3 fatty acids and in vitamins C, D, E and the B vitamins had higher scores on cognitive tests than people with diets low in those nutrients, and moreover that these were dose-dependent, with each standard deviation increase in the vitamin BCDE score ssociated with an increase in cognitive score. Additionally, they showed less brain shrinkage than those with lower intakes of these nutrients.

The B vitamins are often called the B-complex vitamins, and they are a messy sort of group. The main ones of interest for cognition are B12, folate, and choline. Again, most of the research has focused on prenatal development, and age-related cognitive impairment and dementia.

The importance of folate and B12 has a lot to do with homocysteine, which is produced in the body by the breakdown of a dietary protein called methionine. High levels of homocysteine have been linked to increased risk of Alzheimer's, stroke, and vascular dementia, and greater brain shrinkage. B-vitamins are required to convert homocysteine back to methionine, and high levels of homocysteine go hand in hand with low levels of B12 and folate. Diet isn't the only reason for increased levels of homocysteine; smoking has also been implicated. But the association between homocysteine and age-related cognitive decline is not straightforward — it appears that seniors with normal levels of vitamin B12 perform better if their folate levels are high, but when vitamin B12 is low, high levels of folate were associated with poor cognitive performance, as well as a greater probability of anemia. Vitamin B12 is often deficient in older people.

There is also some evidence that B12 is more effective in slowing cognitive decline if levels of omega-3 oils are high.

Folate is a water-soluble B vitamin found particularly in citrus fruit, green leafy vegetables, whole-wheat bread, water-soluble dried beans and peas; however, they are often destroyed by cooking or processing. In the United States, Canada and Australia, flour is fortified with folic acid. Vitamin B12 is naturally found in animal foods including fish, milk and milk products, eggs, meat, and poultry.

Among older adults, choline, particularly in conjunction with omega-3 fatty acids and uridine (not available from food), has been found to improve memory in those cognitively impaired. Top sources of choline are eggs, peanuts, and meat. Fish and soy are also good sources.

References: 

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The Seattle Longitudinal Study of Adult Intelligence

The Seattle Longitudinal Study of Adult Intelligence has followed a group of more than 5000 people for well over four decades. The program began in 1956 and participants have been tested across a whole gamut of mental and physical abilities at seven year intervals since that date.

The study has found:

  • no uniform pattern of age-related change across all intellectual abilities
  • some support for the idea that abilities that are primarily genetically determined tend to decline earlier than abilities that are primarily acquired through schooling or experience (although there may be gender differences here)
    • although abilities that are primarily genetic may decline earlier, abilities acquired through training decline more steeply after late 70s the change in perceptual speed begins in young adulthood and declines in a linear fashion (that is, the rate of decline is constant)
    • the rate and magnitude changes in intelligence seen in those entering old age showed greater decline in the 1st 3 cycles (till 1970); at the same time, younger members are scoring lower on tests at the same age.
    • a decline in psychometric abilities is not reliably observed before 60, but is reliably observed by 74. However, even by 81, fewer than half showed reliable decrements over the past seven years.
    • the size of this decline however is significantly reduced when age changes in perceptual speed are taken into account.
    • substantial cohort / generational differences have been observed. Later-born groups have attained successively higher scores at the same ages for inductive reasoning, verbal meaning, and spatial orientation; however, they’ve scored successively lower in number skill and word fluency (number skill peaked with the 1924 cohort). These changes presumably reflect educational changes.
    • substantial similarity between parents and their adult children and between siblings has been found for virtually all mental abilities and measures of flexibility (the exceptions are the attitude measure of social responsibility, and a measure of perceptual speed). The magnitude of similarity varied for different abilities, and was closer between parent & child than between siblings.
    • the following variables may reduce the risk of cognitive decline in old age:
      • absence of chronic diseases
      • a complex and intellectually stimulating environment
      • a flexible personality style at mid-life
      • high intellectual status of spouse
      • maintenance of high levels of perceptual processing speed
    • cognitive training studies suggested that the observed decline in many community-dwelling older people is probably a function of disuse and is often reversible. Some 2/3 of participants in a cognitive training program showed significant improvement, and 40% of those who had declined significantly were indeed returned to their earlier (pre-decline) level of cognitive functioning. These training gains were retained over seven years.

 

References: 

  1. Schaie, K. Warner 1998. The Seattle Longitudinal Studies of adult intelligence. In M. Powell Lawton & Timothy A. Salthouse (eds) Essential papers on the psychology of aging. NY: NY Univ Pr. Pp263-271.

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Decision-making, working memory, and age

In October I reported on a study that found older adults did better than younger adults on a decision-making task that reflected real-world situations more closely than most tasks used in such studies. It was concluded that, while (as previous research has shown) younger adults may do better on simple decision-making tasks, older adults have the edge when it comes to more complex scenarios. Unsurprisingly, this is where experience tells.

References: 

Mikels, J.A., Löckenhoff, C.E., Maglio, S.J., Carstensen, L.L., Goldstein, M.K. & Garber, A. 2010. Following your heart or your head: Focusing on emotions versus information differentially influences the decisions of younger and older adults. Journal of Experimental Psychology: Applied, 16(1), 87-95.

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Total Cognitive Burden

Because it holds some personal resonance for me, my recent round-up of genetic news called to mind food allergies. Now food allergies can be tricky beasts to diagnose, and the reason is, they’re interactive. Maybe you can eat a food one day and everything’s fine; another day, you break out in hives. This is not simply a matter of the amount you have eaten, the situation is more complex than that.

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Why learning is harder as we get older

Children learn. It’s what they do. And they build themselves over the years from wide-eyed baby to a person that walks and talks and can maybe fix your computer, so it’s no wonder that we have this idea that learning comes so much more easily to them than it does to us. But is it true?

There are two particular areas where children are said to excel: learning language, and learning skills.

References: 

Brown, R. M., & Robertson E. M. (2007). Off-Line Processing: Reciprocal Interactions between Declarative and Procedural Memories. The Journal of Neuroscience. 27(39), 10468 - 10475.

Brown, R. M., Robertson E. M., & Press D. Z. (2009). Sequence Skill Acquisition and Off-Line Learning in Normal Aging. PLoS ONE. 4(8), e6683 - e6683.

Cash, C. D. (2009). Effects of Early and Late Rest Intervals on Performance and Overnight Consolidation of a Keyboard Sequence. Journal of Research in Music Education. 57(3), 252 - 266.

DeKeyser, R., Monner, D., Hwang, S-O, Morini, G. & Vatz, K. 2011. Qualitative differences in second language memory as a function of late learning. Presented at the International Congress for the Study of Child Language in Montreal, Canada.

Dorfberger, S., Adi-Japha E., & Karni A. (2007). Reduced Susceptibility to Interference in the Consolidation of Motor Memory before Adolescence. PLoS ONE. 2(2), e240 - e240.

Ferman, S., & Karni A. (2010). No Childhood Advantage in the Acquisition of Skill in Using an Artificial Language Rule. PLoS ONE. 5(10), e13648 - e13648.

Ferman, S. & Karni, A. 2011. Adults outperform children in acquiring a language skill: Evidence from learning an artificial morphological rule in different conditions. Presented at the International Congress for the Study of Child Language in Montreal, Canada.

Karni, A. 2011. A critical look at ‘critical periods’ in skill acquisition: from motor sequences to language skills. Presented at the International Congress for the Study of Child Language in Montreal, Canada.

Nemeth, D., & Janacsek K. (2010). The Dynamics of Implicit Skill Consolidation in Young and Elderly Adults. The Journals of Gerontology Series B: Psychological Sciences and Social Sciences. 66B, 15 - 22.

Robertson, E. M., Press D. Z., & Pascual-Leone A. (2005). Off-Line Learning and the Primary Motor Cortex. The Journal of Neuroscience. 25(27), 6372 - 6378.

Stambaugh, L. A. (2011). When Repetition Isn’t the Best Practice Strategy: Effects of Blocked and Random Practice Schedules. Journal of Research in Music Education. 58(4), 368 - 383.

Steele, C. J., & Penhune V. B. (2010). Specific Increases within Global Decreases: A Functional Magnetic Resonance Imaging Investigation of Five Days of Motor Sequence Learning. The Journal of Neuroscience. 30(24), 8332 - 8341.

Wymbs, N. F., & Grafton S. T. (2009). Neural Substrates of Practice Structure That Support Future Off-Line Learning. Journal of Neurophysiology. 102(4), 2462 - 2476.

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Memory in normal aging

People are poor at assessing their own memory

One thing research seems to show rather consistently is that, for older adults in particular, beliefs about one's own memory performance have little to do with one's actual memory performance¹. People who believe they have a poor memory are usually no worse at remembering than those who believe they have a good memory.

One theory for why this might be, is that people may be influenced by their general beliefs about how memory changes with age. If you believe that your memory will get progressively and noticeably worse as you get older, then you will pay more attention to your memory failures, and each one will reinforce your belief that your memory is indeed (as expected) getting worse.

Memory decline can be a self-fulfilling prophecy

Research has also shown that common, everyday memory failures tend to be judged more harshly when the failure belongs to an older adult². What is laughed off in a younger adult is treated as an indication of cognitive decline in an older person.

There are ways in which cognitive function (memory, reasoning, problem-solving, etc) declines with age, but it would be fair to say that general belief over-estimates the extent of this. It is, to a large extent, a self-fulfilling prophecy. If you believe deterioration is inevitable, you are not likely to make any effort to halt it.

Memory decline is associated with physical factors

A large-scale study that tracked seniors over a ten-year period found that cognitive decline is not a normal part of aging for most elderly people: 70% of the nearly 6000 seniors in the study showed no significant decline in cognitive function over the ten-year period. These people had two factors in common: they did not carry any of the apolipoprotein E4 genes (often associated with Alzheimer's disease), and they had little or no signs of diabetes or atherosclerosis³.Other factors that have also been implicated in age-related cognitive decline are obesity, smoking, and high blood pressure. Indeed, researchers have suggested that risk factors for cardiovascular disease are also risk factors for cognitive decline: what's bad for the heart is also bad for the brain.

References: 

  1. Hertzog, C. & Dunlosky, J. 1996. The aging of practical memory: an overview. in Herrmann, D.J., McEvoy, C., Hertzog, C., Hertel, P. & Johnson, M.K. (eds). Basic and applied memory research: Vol. 1:Theory in context. NJ: Lawrence Erlbaum.
  2. Erber, J.T., Szuchman, L.T & Rothberg, S. T. 1990. Everyday memory failure: Age differences in appraisal and attribution. Psychology & Aging, 5(2), 236-241.
  3. Haan, M.N., Shemanski, L., Jagust, W.J., Manolio, T.A. & Kuller, L. 1999. The Role of APOE4 in Modulating Effects of Other Risk Factors for Cognitive Decline in Elderly Persons. JAMA, 282, 40-46.

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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.
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