Does
mental stimulation protect you from Alzheimer's and other dementias?
A
number of studies in the past few years have supported the theory that
engaging in mentally stimulating activities can help keep your mind sharp.
Most of these studies have, understandably, been concerned with the effect
of stimulation on the aging mind, and in particular on the question of
whether it helps protect against dementia:
-
one
study found that participation in leisure activities of all kinds was
associated with a risk in dementia risk, although intellectual activities
had the most beneficial effect. (Scarmeas
et al. 2001)
-
a large-scale study of
seniors aged 65 years and older found that participation in
various cognitive activities (such as reading a newspaper) was positively
associated with a decreased risk of developing Alzheimer’s. This effect
remained even after education and occupation (both associated with
Alzheimer's risk) had been taken into account. Physical activity had no
effect. (Wilson et al. 2002b)
-
a large-scale study of
seniors found that more frequent
participation in cognitively stimulating activities (such as reading
books, newspapers or magazines, engaging in crosswords, puzzles, board or
card games, going to museums) was significantly associated with a reduced
risk of Alzheimer’s disease.
(Wilson et al. 2002c)
-
a study involving
seniors aged 75 or older found 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. Only one physical activity had any significant
impact — ballroom dancing — possibly because of the mental demands of
remembering dance steps, responding to music and coordinating with a
partner. (Verghese et al. 2003)
Does mental
stimulation protect you from general age-related cognitive decline?
General
cognitive decline has been found to be less among those seniors who
did more cognitively stimulating activities. In particular, working
memory, perceptual speed, and episodic memory (all processes particularly
affected by aging) were all helped. (Wilson et
al. 2002b)
Another
study followed
a large group of seniors, aged 70-93 at the beginning of the study, over a
seven-year period. Most participants, unsurprisingly, reduced their level
of activity over the period. The rate at which individuals reduced their
activity level was substantially correlated with changes in cognitive and health
measures, although some decline in cognitive performance was evident even
in those who
maintained their activity levels.
(Mackinnon et al. 2003)
In a recent large-scale British study of civil servants
aged between 35 and 55, participation in various leisure activities was
associated with level of cognitive ability. Specifically, regular cultural
visits to theatres, art galleries and stately homes, were associated with
the highest level of cognitive ability, closely followed by reading and
listening to music, then by involvement in clubs and voluntary
organizations, and participation in courses and evening classes. (Singh-Manoux et al.
2003)
Interestingly, this
particular study found that the association between the selected 13
leisure activities and cognitive ability was slightly stronger for men
than for women. One reason for this may be that women are more likely to
engage in activities other than those selected.
In particular, it has
been speculated that women are more likely to engage in more social
interaction, which may be beneficial. There is some evidence that social
interactions benefit cognitive functioning.
Just talking may help prevent cognitive
decline
"Social engagement" can be
measured by how often people talk on the phone with friends, neighbors and
relatives, how often they get together with them, how many people they can
share their most private feelings and concerns with. A series of studies
by Dr Oscar Ybarra (as yet unpublished) have found that, across all age
groups, the more socially engaged people are, the lower their level of
cognitive impairment and the better their working memory performance.
This does not necessarily mean that more
social contact leads to a sharper mind. People in better shape mentally
are probably more inclined to be social in the first place.
However, the studies do build on earlier
research. One study found that seniors who reported more demands from
social relationships had better cognitive functioning. This may reflect
the benefit of complex social interaction (or of course, it may simply
reflect the fact that those with better cognitive function are more likely
to have demands made on them). (Seeman et al. 2001)
Social engagement also appears to have an
effect on health. A study growing out
of the Seattle Longitudinal Study
found low levels of social networks
were associated with more hospital and doctor visits, and higher health
costs. Those with greater health problems were more likely to be socially
isolated, and also had lower levels of education and income. (Bosworth
& Schaie, 1997)
Personality
variables also play a role
The
association between all these factors is assuredly complex. One aspect to
it may be that people with low self-worth may be less likely to engage in
stimulating activities (social, intellectual, and physical). Recent
research has found that age-related cognitive decline is more likely in
those with low self-worth, and that the brains of those with less
self-worth were significantly smaller than those of people who felt good
about themselves. So perhaps those with low self-worth don’t bother to
do much, and their brains shrink, reflecting this lack of use, in the same
way that our stomachs shrink when we feed them less.
(Lupien,
2003)
Self-worth is also
associated with anxiety and depression, and these factors have been shown
to be associated with an increased risk of developing Alzheimer's in
several studies:
-
a
seven-year study found that those
with the greatest number of depressive symptoms at the start of the
study were more likely to develop Alzheimer's disease and also showed
more rapid cognitive decline. (Wilson et al.
2002a)
-
a
longitudinal study found that those who most often experience negative
emotions like depression and anxiety were twice as likely to develop Alzheimer's
disease as those who were least prone to experience negative emotions.
(Wilson et al. 2003)
-
a
study of Alzheimer’s patients found that their level of
impairment in episodic memory on initial evaluation was related to
their tendency to experience psychological distress (as assessed by a
knowledgeable informant) prior to developing Alzheimer’s. This was
not, however, a factor in the rate at which cognitive function
declined over the course of the disease. (Wilson et al.
2004)
A
person’s tendency to experience psychological distress has been shown to
be a stable personality trait throughout adulthood. In the second study,
proneness to stress was specifically associated with a decline in episodic
memory (measured by asking participants to recall a list of words or a
story) — an area particularly problematic for those with Alzheimer's.
Episodic memory ability declined 10 times faster in those high in
proneness to distress than in those low in this
response.
This
result was not altered when participants’ engagement in cognitively
stimulating activities was taken into account, suggesting that this
personality factor is independent of activity level.
The
way in which we respond to stress may also change as we get older, and
this may contribute to poorer memory performance in old age. A study involving 14
healthy seniors compared memory performance on two tasks, one of them
assumed to be stressful (a public speaking task) and one not (an
attentional task). It was found that declarative memory (conscious
recollection of learned information) was impaired on the stressful task,
but not on the nonstressful task. Nondeclarative memory (information
retrieved without conscious or explicit effort) was not affected by
stress. Measurement of cortisol levels suggested that it was the
anticipation of stress rather than the stress itself that affected memory.
It is speculated that an altered
cortisol responsivity to acute and/or chronic stress may be
partly responsible for age-related cognitive decline. (Lupien et al.
1997)
But what do all these
studies really mean? It must always be remembered that correlation doesn't
mean causation. The fact that depressed people are more likely to develop
Alzheimer's doesn't mean depression causes Alzheimer's. Physical
changes in the brain that occur long before symptoms appear may also make
it more likely that the individual will suffer depression, for example.
The fact that people who lead busier, more active and involved lives, tend
to perform better on memory and cognitive tasks, doesn't mean that it is
their activities that keep their minds sharp. It may be that those whose
minds are sharp are more likely to engage in such activities.
Is higher mental ability protective
against cognitive impairment?
The main problem with
determining the relationship between cognitive activities and cognitive
performance is that we don’t usually know the previous history of
cognitive performance. Level of education, occupation, socio-economic
class, these are all indicators, but to know whether a person engages in
more cognitive activities because he is intellectually able, or whether he
has retained more mental ability because he has kept himself mentally
active, we really need to know his cognitive abilities at an earlier age.
A recent longitudinal
study bears on this question (unfortunately, only preliminary results are
as yet available). The Scottish Mental Survey assessed 87,498
eleven-year-olds in 1932, and another 70,805 in 1947. In a fascinating
follow-up to this study, over 1000 of these students were contacted and
re-assessed, on the exact same tests. It was found that, first of all, the
seniors did rather better than they had at age 11, and more importantly,
that differences in mental ability remained fairly stable with age — “with
some interesting exceptions, the high scorers did well and the modest
remained so.” (Deary, 2003)
A study of 215 seniors
aged 66-75 found that those with a larger head size had significantly
higher scores on intelligence tests, and also showed less decline in
memory performance over the 3 ½ year follow-up period. Those with the
smallest heads had a fivefold increased risk of cognitive decline compared
to those with the largest. However, there was no correlation with head
size at birth, indicating that it is brain development in the early years
that is important. During the first year of life, babies' brains double in
size, and by the time they are six, their brain weight has tripled. These,
it appears, are the crucial years for laying down brain cells and neural
connections (pointing to the importance of providing both proper
nourishment and intellectual stimulation in these early years).
(Gale et al. 2003)
There is also evidence
that the more formal education you have, and the greater your head size
(reflecting brain size), the more you are protected from the effects of
Alzheimer’s. That is, these factors don’t reduce your likelihood of
developing Alzheimer’s, but, by providing reserve brain capacity — a
“cognitive reserve” — normal function can be retained for longer. (Mortimer et al.
2003; Bennett et al. 2003)
Interestingly, a
longitudinal study found that those who wrote more densely (packed more
ideas into the sentences) of autobiographical essays written when they
were young were less likely to get Alzheimer's disease six decades later.
( Early language ability may be linked to
lower risk of Alzheimer's )
However, it must also
be remembered that the effects of education and occupation on Alzheimer's
risk seem to be greatly reduced when you take into account mentally
stimulating activities (Wilson, 2002b). That is, those with higher levels
of education and higher income are more likely to engage in mentally
stimulating activities, and this accounts for much (though not all) of the
effects of education and occupation.
Clearly all these factors impact on each
other: physical health, cognitive function, social engagement, depression,
self-worth, income, education. It does seem most plausible, however,
that stimulation is a critical factor. Stimulation in the early years
grows complex brains (builds more neurons and richer networks of
connections between them). Education may be presumed to provide
stimulation - thus, more years of formal education would correlate with
more years of stimulation, as well as providing training that encourages
the individual to continue to find mental stimulation rewarding.
Occupation similarly, can also readily be seen to be correlated with level
of stimulation.
Why should mental stimulation help
prevent cognitive decline?
Stimulation clearly
helps the growing brain. But why should stimulating activities help the
aging brain? One reason may be that stimulation helps older brains retain sufficient
flexibility to
compensate for difficulties it experiences by finding different ways
of doing things. Keeping the brain
active with a variety of cognitive tasks may be one way to retain flexibility. Imaging studies have provided evidence
that better-performing seniors show different patterns
of brain activity compared to both younger adults and poorer performing
seniors, implying that those who perform well in old age are those who
have found new ways of processing information. (Cabeza et al.
2002)
Activities such as
reading, doing crosswords, indeed anything that uses language and keeps
you meeting new words, have also been suggested as helping reduce the
occurrence of those occasions when you feel you know something, “on the
tip of your tongue”, but can’t quite recall it. Participation in such
activities is thought to help by keeping your memory links strong.
(James &
Burke, 2001)
My own
opinion is that mental stimulation is absolutely critical at all stages of
one's life - in infancy and childhood, in early adulthood and middle life,
and in old age. While the whole question of neurogenesis (the making of
new nerve cells) in adult brains is still unclear, there is no question
that connections between neurons continue to be made throughout one's
life. We know that connections are stronger when they are used, and grow
weak when they have not been used for a long while. We know that the more
connections there are, the more possible paths to a memory there are. How
could it not be, that the more you use existing connections, and the more
connections you make, the easier it will be to remember and think?
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. June
news report
Bosworth, H.B. &
Schaie, K.W. 1997. The relationship of social environment, social
networks, and health outcomes in the Seattle Longitudinal Study: two
analytical approaches. Journals of Gerontology Series B: Psychological
Sciences and Social Sciences, 52 (5), 197-205.
Cabeza, R., Anderson,
N.D., Locantore, J.K. & McIntosh, A.R. 2002. Aging Gracefully:
Compensatory Brain Activity in High-Performing Older Adults. NeuroImage,
17(3), 1394-1402. November
news report
Deary,
I. 2003. These
preliminary findings were presented by Professor Ian Deary from the
Department of Psychology, University of Edinburgh at a symposium on aging
at the Australian National University. http://dsc.discovery.com/news/afp/20030929/aging.html
Gale, C.R., Walton, S.
& Martyn,
C.N. 2003. Foetal and postnatal head growth and risk of cognitive
decline in old age. Brain, 126, 2273-2278.
http://observer.guardian.co.uk/uk_news/story/0,6903,1051264,00.html
James, L.E. &
Burke, D.M. 2001. Phonological Priming Effects on Word Retrieval and
Tip-of-the-Tongue Experiences in Young and Older Adults. Journal
of Experimental Psychology: Learning, Memory and Cognition, 26 (6), 1378-1391.
Full text available at: http://www.apa.org/journals/xlm/xlm2661378.html
Lupien,
S. 2003. Study presented at a
conference at the Royal Society in London. (Reported on BBC News Online,
20/11/2003)
Lupien,
S.J., Gaudreau, S., Tchiteya, B.M., Maheu,
F., Sharma, S., Nair, N.P.V., Hauger,
R.L., McEwen, B.S. & Meaney, M.J. 1997. Stress-Induced Declarative Memory Impairment in Healthy Elderly
Subjects: Relationship to Cortisol Reactivity. The Journal of Clinical
Endocrinology & Metabolism, 82 (7), 2070-2075.
Mackinnon, A.,
Christensen, H., Hofer, S.M., Korten, A.E. & Jorm, A.F. 2003. Use It
and Still Lose It? The Association Between Activity and Cognitive
Performance Established Using Latent Growth Techniques in a Community
Sample. Aging Neuropsychology and
Cognition, 10 (3), 215-229.
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.
July 2003
news report
Scarmeas, N., Levy, G.,
Tang, M-X., Manly, J. & Stern, Y. 2001. Influence of leisure activity
on the incidence of Alzheimer’s Disease. Neurology, 57,
2236-2242. December
news report
Seeman,
T.E., Lusignolo, T., Berkman, L., Albert ,M. 2001. Social Environment
Characteristics and Patterns of Cognitive Aging:
MacArthur Studies of Successful Aging. Health Psychology, 20,
243-255.
Singh-Manoux,
A., Richards, M. & Marmot, M. 2003. Leisure activities and cognitive
function in middle age: evidence from the Whitehall II study. Journal
of Epidemiology and Community Health, 57, 907-913. November
2003 news report
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.
June 2003 news
report
Wilson,
R.S., Fleischman, D.A., Myers, R.A., Bennett, D.A., Bienias, J.L., Gilley,
D.W. & Evans, D.A. 2004. Premorbid
proneness to distress and episodic memory impairment in Alzheimer's
disease. Journal of Neurology, Neurosurgery, &
Psychiatry, 75(2), 191-5.
Wilson, R.S., Evans, D.A.,
Bienias, J.L., Mendes de Leon, C.F., Schneider, J.A. & Bennett, D.A.
2003. Proneness to psychological distress is
associated with risk of Alzheimer’s disease. Neurology, 61,
1479-1485. News
report
Wilson,
R.S., Barnes, L.L., de Leon, C.F.M., Aggarwal, N.T., Schneider, J.S.,
Bach, J., Pilat, J., Beckett, L.A., Arnold, S.E., Evans, D.A. &
Bennett, D.A. 2002a. Depressive
symptoms, cognitive decline, and risk of AD in older persons.
Neurology, 59, 364-370. News
report
Wilson, R.S., Bennett,
D.A., Bienias, J.L., Aggarwal, N.T., de Leon, M.C.F., Morris, M.C.,
Schneider, J.A. & Evans, D.A. 2002b. Cognitive activity and incident AD
in a population-based sample of older persons. Neurology, 59,
1910-1914. December
news report
Wilson, R.S., de Leon,
M.C.F., Barnes, L.L., Schneider, J.A., Bienias, J.L., Evans, D.A. &
Bennett, D.A. 2002c. Participation
in Cognitively Stimulating Activities and Risk of Incident Alzheimer
Disease. JAMA, 287, 742-748.
February 2002
news report
Ybarra, O. not yet
published
http://www.eurekalert.org/pub_releases/2002-10/uom-sig102202.php
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