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                                                                                                                                                   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
                                                                                                                                                   lacking replication.
                                                                                                                                                       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).
          questions




                       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
          resources




                           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,
          references




                       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                                              nazimek@care2.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.




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