the presence of stroke are less sensitive), or
perhaps physical activity affects differently
different types of dementia. Similarly, there
is evidence that exercise can counteract
genetic susceptibility to Alzheimer’s disease
Active body, healthy mind (Rovio et al., 2005), although this result is
Overall, there is evidence showing that
regular exercise reduces risk of dementia,
Jadwiga Nazimek on whether exercise can delay – or even prevent – dementia but the area is plagued by methodological
problems and incomplete knowledge about
biological mechanisms of the effects of
Exercise is a good treatment t’s a normal part of ageing that many physical activity on cognitive functioning.
for many health problems, both
physical and mental. It reduces
physical frailty and might prolong
I will be familiar with: as we get older,
memory, visuospatial ability and
executive function (planning, scheduling, How does exercising improve
the lifespan, but (in synergy with working memory, inhibition and thinking?
other factors, such as lifestyle or multitasking) tend to suffer. Indeed, their One mechanism is the growth of new
genetics) it can improve the quality impairment is one of the first symptoms neurons (neurogenesis) and the plasticity
of later life by preserving healthy of Alzheimer’s disease. But could a of the connections between the neurons
intellectual functioning and healthy lifestyle be the key to keeping a (synaptic plasticity). Mice who exercise
preventing – or at least delaying – healthy mind? are better at learning spatial and memory
dementia. It appears that older adults who task than their sedentary counterparts
This knowledge is exceedingly exercise regularly and enjoy higher level of (Cotman & Berchtold, 2007). This effect,
valuable in the face of the growing physical fitness perform better on cognitive however, takes place only if a signalling
proportion of older adults in tasks involving these functions than do molecule called brain-derived
modern society and the growing their sedentary peers (e.g. Kramer et al., neurotrophic factor is present. The
burden of dementia. So how can 2006). What’s more, aerobic exercise seems neurotrophic factor supports survival and
exercise reduce the risk of to be considerably more beneficial than plasticity of existing neurons. ‘Long-term
dementia, and what can non-aerobic activity (Jedrziewski et al., potentiation’, thought to be the cellular
psychologists do to encourage 2007). Thus, aerobic exercise appears to mechanism of learning, occurs when
people who fail to exercise? help to counterbalance the effects of ageing repetitive stimulation results in increased
on higher-order cognitive function. potentiation of the synapse – the synaptic
It is not only the normal effects of response to the stimuli is stronger and
ageing that can be reduced by regular lasts longer. This phenomenon is
physical activity: some studies (e.g. impaired in mice lacking the
How would lack of exercise affect the
Rockwood & Middleton, 2007) suggest neurotrophic factor (Korte et al., 1995).
cognitive development of children? the risk of mild cognitive impairment can Therefore, by supporting long-term
be reduced, with others finding that the potentiation, the neurotrophic factor
Is there a difference in levels of exercise risk of Alzheimer’s disease can be lowered appears to play a role in memory and
between men and women, and if so, by up to 30 per cent (Jedrziewski et al., learning (Cotman & Berchtold, 2007).
does it translate into differences in the 2007). Evidence, however, is still The neurotrophic factor is also involved
risk of dementia? inconsistent: in some studies physical in the growth and survival of new
activity has no effects on the risk of neurons and synapses in the
vascular dementia, where the blood flow to hippocampus (the seat of memory and
http://nihseniorhealth.gov/stories/ the brain is insufficient to maintain healthy learning) and cortex (responsible for
stories.html cells (Rockwood & Middleton, 2007). In thinking).
Kramer, A., Erickson, K.I. & Colcombe, others, exercise is associated with a lower The fact that levels of the neurotrophic
S.J. (2006). Exercise, cognition, and
the aging brain. Journal of Applied
risk of vascular dementia, but not that of factor are 30–80 per cent lower in people
Physiology, 101, 1243–1251. Alzheimer’s disease (Ravaglia et al., 2007). suffering from Alzheimer’s disease suggests
This might be related to definitions of its involvement in the pathology of the
vascular dementia (e.g. those relying on illness (Murray et al., 1994). In rodents,
Barnes D.E., Jaffe, K., Satariano, W.A. & 853–861. Preventative Medicine, 25, 172–183. Cotman, C.W. & Berchtold, N.C. (2007).
Tager, I.B. (2003). A longitudinal study of Bezzi, P., Domercq, M., Brambilla, L. et al. Broe, G.A., Creasey, H., Jorm, A.F. et al. Physical activity and the maintenance of
cardiorespiratory fitness and cognitive (2001). CXCR4-activated astrocyte (1998). Health habits and risk of cognition. Alzheimer’s and Dementia, 3,
function in healthy older adults. Journal glutamate release via TNF. Nature cognitive impairment and dementia in 30–37.
of the American Geriatrics Society, 51, Neuroscience, 4, 702–710. old age. Australian and New Zealand Dik, M.G., Deeg, D.J.H., Visser, M. & Jonker,
459–465. Blood may help us think. (2007, 17 Journal of Public Health, 22, 621–623. C. (2003). Early life physical activity and
Berchtold, N.C., Chinn, G., Chou, M. et al. October). ScienceDaily. Retrieved 11 Dec Brookmeyer, R., Gray, S. & Kawas, C. cognition at old age. Journal of Clinical
(2005). Exercise primes a molecular 2008 from tinyurl.com/bqhg6c (1998). Projections of Alzheimer’s in the and Experimental Neuropsychology, 25,
memory for brain-derived neurotrophic Brawley, L.R., Rejeski, W.J. & King, A.C. US and the public health impact of 643–653.
factor protein induction in the brain (2003). Promoting physical activity for delaying disease onset. American Jedrziewski, M.K., Lee, V.M.Y. &
hippocampus. Neuroscience, 133, older adults. American Journal of Journal of Public Health, 88, 1347–1342. Trojanowski, J.Q. (2007). Physical
206 vol 22 no 3 march 2009
exercise and dementia
exercise increases the levels of the exercise significantly increases levels of physical activity lowers the risk of
neurotrophic factor (Berchtold et al., certain chemokines in the brain. These cerebrovascular disease and helps to
2005), as well as the growth and flexibility chemokines protect neurons in the fight the vascular risk factors (such as
of neurons (van Praag et al., 1999). The hippocampus from death induced by the hypertension) which increase the risk of
two processes – neurogenesis and synaptic plaques, as well as improve incidence and progression of Alzheimer’s
plasticity – might interact, so that the communication between brain cells (Bezzi disease and vascular dementia. By
growth of new cells contributes to the et al., 2001). However, the exact increasing cerebral blood flow, exercise
improved plasticity of the synapses (van mechanism of the effect of exercise on helps to reduce damage to the neurons
Praag et al., 1999), and learning supports inflammatory response in the brain resulting from oxidative stress (excess of
the survival of the newborn cells (Tashiro remains unclear (Parachikova et al., 2008). toxic free radicals) present in the early
et al., 2007). Exercise also improves blood flow in stages of Alzheimer’s disease (Lange-
The effect of exercise on the birth the brain, therefore influencing the amount Asschenfeldt & Kojda, 2008). Finally,
and survival of new neurons appears to and concentration of nutrients such as angiogenesis (the growth of new
be related to the presence of a protein oxygen and glucose, as well as the capillaries) as a result of exercise protects
hormone similar to insulin (the insulin- expanding and contracting movement of neurons via substances such as vascular
like growth factor 1 or IGF-I), which the cerebral vessels, which in turn affects endothelial growth factor. The latter is
regulates metabolism, as well as growth, brain cells. Blood delivers nutrients such involved in production and release of the
multiplication and death of cells. Physical as oxygen and glucose, essential for the brain-derived neurotrophic factor from one
activity increases the uptake of IGF-I into neurons to function. In addition, blood of its sources, the brain microvascular
to the brain, including the hippocampus carries factors that affect neural activity, endothelial cells.
(Trejo et al., 2001). Mice in whose brains and their concentration might depend on Therefore, neurogenesis interacts with
IGF-I is insufficient suffer angiogenesis, and by improving the
from reduced neurogenesis health of the vascular system,
and problems with spatial exercise helps to protect neurons
learning. In these animals and might delay the occurrence of
moderate treadmill running dementia.
exercise has no effect on the
deficits, but they can be
eliminated by the How much and how often?
administration of the insulin- As a guide, exercise appears to
like growth factor (Trejo et al., reduce the risk of dementia by 32
2007). per cent provided it takes place
The immune system is three or more times a week
another party in the (Rockwood & Middleton, 2007).
interaction between exercise Each session should last at least
and thinking. Increased level 20 minutes, be vigorous, and
of inflammatory factors is cause breathlessness and sweating
highly associated with (Jedrziewski et al., 2007).
cognitive impairment in Some studies suggest there is
Alzheimer’s disease, where By exercising, young men can protect their future a dose–response relationship, in the
brain cells die as a result of the cognitive ability sense that the group with lowest levels
build-up of abnormal protein in of exercise is at the greatest risk, while
plaques and tangles the group with highest levels of exercise
(Parachikova et al., 2007). Sedentary, aged the volume of the blood flow. Brain is at lowest risk (e.g. Rockwood &
mice, in whose brains the Alzheimer’s cells might react to the expanding and Middleton, 2007). Other studies suggest
disease pathology is already present, have contracting movement of the blood that the benefits from exercise, in terms of
higher levels of inflammation compared to vessels. Finally, blood affects neurons by risk of dementia, increase in the
healthy mice the same age. After three regulating the temperature of the brain dose–response manner up to the moderate
weeks of voluntary wheel running, tissue (‘Blood may help us think’, 2007). level, and then the benefits cease (e.g.
however, the diseased mice regain normal Thus, by improving the cerebral blood Larson et al., 2006). Finally, exercising at
working and spatial memory (Parachikova flow, exercise is likely to improve the the age of 15–25 years can protect
et al., 2008). This might be because function of the brain. Moreover, regular cognitive ability in later life, at least in men
activity and cognitive health. Alzheimer’s Lange-Asschenfeldt, C. & Kojda, G. (2008). regulation of brain-derived neurotrophic changes parallel the early stages of
and Dementia, 3, 98–108. Alzheimer’s disease, cerebrovascular factor and type II calcium/calmodulin- Alzheimer disease. Neurobiology of
Korte, M., Carroll, P., Wolf, E. et al. (1995). dysfunction and the benefits of exercise. dependent protein kinase messenger Aging, 28, 1821–1833.
Hippocampal long-term potentiation is Experimental Gerontology, 43, 499–504. RNA expression in Alzheimer’s disease. Parachikova, A., Nichol, K.E. & Cotman,
impaired in mice lacking brain-derived Larson, E.B., Wang, L., Bowen, J.D. et al. Neuroscience, 60(1), 37–48. C.W. (2008). Short-term exercise in
neurotrophic factor. Proceedings of the (2006). Exercise is associated with reduced O’Brien Cousins, S. & Gillis, M.M. (2005). aged Tg2576 mice alters neuro-
Nat. Acad. of Sciences, 92, 8856–8860. risk for incident dementia among ‘Just do it… before you talk yourself out inflammation and improves cognition.
Kramer, A., Erickson, K.I. & Colcombe, S.J. persons 65 years of age and older. of it’. Psychology of Sport and Exercise, 6, Neurobiology of Disease, 30, 121–129.
(2006). Exercise, cognition, and the Annals of Internal Medicine, 144, 73–83. 313–334. Payne, N., Jones, F. & Harris, P. (2002).
aging brain. Journal of Applied Murray, K.D., Gall, C.M., Jones, E.G. & Parachikova, A., Agadjanyan, M.G., Cribbs, The impact of working life on health
Physiology, 101, 1243–1251. Isackson, P.J. (1994). Differential D.H. et al. (2007). Inflammatory behavior. Journal of Occupational Health
read discuss contribute at www.thepsychologist.org.uk 207
exercise and dementia
(Dik et al., 2003), and exercising in midlife threshold of exercise for the elderly, who change model and group teaching of
can be just as beneficial as that in later life can find it difficult to get the appropriate cognitive and behavioural strategies.
(Rockwood & Middleton, 2007). levels of activity (Cotman & Berchtold, Participants, encouraged to spend less time
2007). Occupational psychologists on sedentary activities such as watching
investigate how high-strain work prevents television, often choose to replace them
Preventing or delaying? exercise in even those employees who with more intense activities, such as
Even though the evidence that physical intend to be more physically active, by walking. Teaching the skill of self-
activity has good effect on cognitive affecting their confidence and self-efficacy monitoring can also successfully increase
function is robust, there are some at motivational stage, as well putting their physical activity. Combining individual
inconsistencies and good intentions into interventions with those aimed at the
methodological problems. practice (Payne et al., community (e.g. via healthcare providers)
Some studies find that 2002). Suggested and those directed by the state (tax
physical activity is unrelated solutions include incentives, constructing neighbourhood
to cognitive function (e.g. flexible working hours sidewalks) can create a social-ecologic,
Broe et al., 1998; Yamada et and convenient multiple-level approach. In fact, some
al., 2003). This might be due facilities, such as an exercise psychologists work as consultants
to using self-report data onsite gym. for initiatives of the government and NHS
concerning exercise, not In order to in promoting exercise and providing
distinguishing aerobic from encourage exercise training to those involved.
non-aerobic activity, lack of in the frame of health
assessment of duration, promotion (usually
intensity and frequency cardiovascular), Challenges ahead
of activities and failure to exercise and health It appears that regular physical activity can
eliminate participants with psychologists analyse reduce the risk of dementia, provided that
subclinical dementia (Kramer factors that influence it takes the appropriate form and is
et al., 2006). Other common motivation and undertaken with sufficient frequency
difficulties include lack of perseverance in and duration. At this stage of research,
agreed definitions and criteria keeping fit, as well as however, many issues are not clear; for
of physical fitness and barriers and ways of example, inconsistencies of evidence
dementia (e.g. single disease entity promoting physical activity. Sometimes concerning effects of exercise on different
versus categories; Jedrziewski et al., 2007; those younger adults who are willing to types of dementia might be due to
Rockwood & Middleton, 2007). engage in physical activity might only methodological problems, but also lack of
Finally, the lack of an accepted need some simple encouraging triggering knowledge about the biological processes
definition of ‘prevented dementia’ makes it messages (‘Just do it’, ‘Don’t think about evoked by exercise in the brain. These
difficult to determine whether a particular it’), others need help in getting started and processes might, again, depend on the type
method is successful or not in this reminders (O’Brien et al., 2005). However, of exercise and affect individual brains
endeavour. It has been suggested that the elderly should seek appropriate differently. Psychologists investigate factors
delaying dementia equals preventing it, medical advice before undertaking related to exercise and on the basis of these
since dementia occurs in late stages of life exercise. can suggest solutions. Challenges include
– delaying it by two years would reduce More difficult to tackle can be barriers linking the individual strategies to
prevalence by 25 per cent (Brookmeyer et such as unsafe neighbourhood, perceived population-wide programmes that promote
al., 1998). However, physical activity illness and physical disability and gender, healthy lifestyle and to group programmes
reduces physical frailty in older people and but also cultural stereotypes of older adults of social problem-solving.
thus might prolong lifespan, therefore as frail and dependent (Brawley et al.,
actually serving to increase the prevalence 2003). Gaining confidence and increasing
of dementia! self-efficacy via programmes such as the I Jadwiga Nazimek
group-mediated cognitive-behavioural is a psychology graduate
approach, can help older adults overcome studying for an MSc in
What can psychologists do? these barriers (Rejeski et al., 2003). Other biomedicine at Lancaster
Neurocognitive knowledge of how group strategies, described by Brawley and University
exercise affects the brain can help work colleagues (2003), include lifestyle email@example.com
on techniques that would lower the intervention, which involves stages of
Psychology, 7(4), 342–353. Rovio, S., Kåreholt, E., Helkala, E. et al. Trejo, J.L., Llorens-Martín, M.V. & Torres- Neuroscience, 27(12), 3252–3259.
Ravaglia, G., Forti, P., Lucicesare, A. et al. (2005). Leisure-time physical activity at Alemán, I. (2008). The effects of exercise van Praag, H., Christie, B.R., Sejnowski,
(2007). Physical activity and dementia in midlife and the risk of dementia and on spatial learning and anxiety-like T.J. & Gage, F.H. (1999). Running
the elderly. Neurology, 70, 1786–1794. Alzheimer’s disease. The Lancet behavior are mediated by an IGF-I- enhances neurogenesis, learning, and
Rejeski, W.J., Ambrosius, W.T., Brubaker, Neurology, 4, 705–711. dependent mechanism related to long-term potentiation in mice.
P.H. et al (2003). Older adults with chronic Trejo, J.L., Carro, E. & Torres-Alemàn, I. hippocampal neurogenesis. Molecular Proceedings of the National Academy of
disease. Health Psychology, 22, 414–423. (2001). Circulating insulin-like growth and Cellular Neurosciences, 37, 402–411. Science, 96, 13427–13431.
Rockwood, K. & Middleton, L. (2007). factor I mediates exercise-induced Tashiro, A., Makino, H., Gage, F.H. (2007). Yamada M., Kasagi, F., Sasaki, H. et al.
Physical activity and the maintenance increases in the number of new Experience-specific functional (2003). Association between dementia
of cognitive function. Alzheimer’s and neurons in the adult hippocampus. modification of the dentate gyrus and midlife risk factors. Journal of the
Dementia, 3, 38–44. Journal of Neuroscience, 21, 1628–1634. through adult neurogenesis. Journal of American Geriatrics Society, 51, 410–414.
208 vol 22 no 3 march 2009
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