Exercise programs for people with dementia

Abstract

In 2012, the World Health Organization declared dementia to be a public health priority (World Health Organization 2012), citing the high global prevalence and economic impact on families, communities, and health service providers. In the coming decades, with the aging of the population, the number of individuals living with dementia in our communities will rise dramatically. This will increase the burden on family caregivers, community care, and residential care services (Alzheimer Society of Canada 2010; World Alzheimer Report 2011). People diagnosed with dementia often have unique needs, as they tend to be older and present with acquired impairment in memory, associated with other disturbances of higher cortical function, or personality changes (APA 1995; McKhann 1984). As a first approach, best practice guidelines currently recommend the exploration of behavioural and psychological interventions before initiating pharmacological interventions, due to the limited benefit of pharmacological treatments in reducing functional decline and their potential side effects (Forbes 2008a; Hogan 2008). Exercise is among the potential protective lifestyle factors identified as a strategy for treating the symptoms of dementia or delaying its progression (Lautenschlager 2010).

How the intervention might work

Physical activity, as defined for this review, refers to “body movement that is produced by the contraction of skeletal muscles and that increases energy expenditure” (Chodzko-Zajko 2009). Exercise refers to “planned, structured, and repetitive movement to improve or maintain one or more components of physical fitness” (Chodzko-Zajko 2009). There are several potential mechanisms that link exercise programs, which include physical activity to cognitive function. A detailed examination of the potential mechanism(s) is beyond the scope of this review. For further information the reader is directed to two recent reviews, Erickson 2012 and Davenport 2012. Briefly, exercise improves vascular health by reducing blood pressure (Fleg 2012), arterial stiffness (Fleg 2012), oxidative stress (Covas 2002), systemic inflammation (Lavie 2011), and enhances endothelial dysfunction (Ghisi 2010), all of which are associated in the maintenance of cerebral perfusion (Churchill 2002; Davenport 2012; Rogers 1990). Recent evidence has shown a strong association between cerebral perfusion (i.e. balance between the supply and demand of nutrients to the brain), cognitive function, and fitness in older healthy adults (Brown 2010). Furthermore, insulin resistance or glucose intolerance is linked with amyloid β plaque formation (Farris 2003; Wareham 2000; Watson 2003), which is a feature of AD. Exercise is known to enhance insulin sensitivity and glucose control (Ryan 2000). Exercise may also preserve neuronal structure and promote neurogenesis, synaptogenesis, and capillarization (formation of nerve cells, the gaps between them, and blood vessels, respectively) (Colcombe 2003), which may be associated with exercise-induced elevation in brain-derived neurotrophic factor (BDNF) (Vaynman 2004), and insulin-like growth factors (Cotman 2007). Animal and human studies investigating the role of BDNF provide evidence that BDNF supports the health and growth of neurons and may regulate neuroplasticity (adaptability of the brain) as we age (Cheng 2003; Vaynman 2004). Intlekofer 2012 recently reported that exercise reinstates hippocampal function by enhancing the expression of BDNF and other growth factors that promote neurogenesis, angiogenesis (formation of blood vessels), and synaptic plasticity. Taken together, animal and human studies indicate that exercise provides a powerful stimulus that can counteract the molecular changes that underlie the progressive loss of hippocampal function in advanced age and AD (Erickson 2012).

Summary of main results

This review included 16 trials (17 articles) with a total of 937 participants. Most participants were older people with AD. The exercise programs varied greatly; the length of time that they ran ranged from two weeks to 12 months, and activities varied (e.g. hand movements, sitting, walking, and upper and lower limb exercises). The review suggests that exercise programs may have a significant impact on improving cognitive functioning and the ability to perform ADLs in people with dementia. There was substantial and considerable unexplained statistical heterogeneity observed in the cognitive and ADL analyses, respectively, which suggests the need for caution in interpreting these results. Indeed, when we removed the Venturelli 2011 trial from the cognitive analysis - since it was the only trial that included only people with moderate to severe dementia - the heterogeneity was reduced, and the results of this meta-analysis were no longer significant. In addition, our findings reveal that the burden experienced by informal caregivers providing care in the home may be reduced if they supervise their family member with dementia during participation in an exercise program. This review found no significant effect of exercise on challenging behaviours or depression. Nevertheless, these are encouraging results, as dementia is a debilitating disease that results in progressive decline in cognition and ability to perform ADLs, as well as other symptoms. A slowing of both cognitive decline and the development of dependence in ADLs is critical for enhancing the quality of life for people with dementia, and will have an impact on the family caregivers’ ability to sustain their caregiving role.

  Dorothy Forbes,
  Emily J Thiessen,
  Catherine M Blake,
  Scott C Forbes,
  Sean Forbes