Mental stimulation

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.