Introduction

The incidence and prevalence of dementia are expected to increase dramatically in the coming decades. In the absence of curative treatment, risk factor modification remains the cornerstone for dementia prevention. Population studies and randomized controlled trials have recently indicated that people who are cognitively, socially and physically active have a reduced risk of cognitive impairment. Dementia is now considered as a long process resulting from accumulation of both risk and protective factors during lifespan (Figure 77.1).1 Physical activity appears to be one of the main factors that contribute to the maintenance of a healthy ageing brain. Basic research trials also confirmed that an enriched environment and physical activity enhance the proliferation of new brain cells and promote brain repair in animal models.2 Some of the most promising strategies for the prevention of dementia include vascular risk factor control, but also cognitive activity and physical activity.

Figure 77.1 Alzheimer’s disease and the potential roles of physical activity during lifespan.

Physical activity is already known as a cost-effective practice that has demonstrated during the past 30 years numerous physical benefits in the field of heart disease and cancer. The benefits of physical activity on brain functioning have been reported more recently.

Results from clinical and basic research facilitated by new technological approaches such as functional magnetic resonance imaging (fMRI) support the benefit of physical activity on cognitive decline in humans. However, none of the clinical research has clearly demonstrated that physical activity can prevent dementia. Nevertheless, growing evidence supports the view that physical activity may, at least, slow cognitive decline. Even a small delay of the onset of cognitive decline or a slowing of the disease progression would have a significant impact on this major public health priority.

Physical activity has also been shown to improve function even in frail nursing home residents3 and Alzheimer’s disease (AD) patients.4 Physical activity yields an important and potent protective factor against functional decline and various frequent and devastating complications of the disease such as falls, fractures, malnutrition and behavioural disturbances, such as depression and anxiety. For demented patients, physical activity may also prevent key problems and have a major impact on the burden of the disease and quality of life.

Physical Activity and The Prevention of Dementia in Clinical Research

Table 77.1 reports most of the longitudinal epidemiological studies published during the past 10 years which have evaluated the association between physical activity and dementia or cognitive decline. Most of these epidemiological studies were controlled for potential confounders and suggest a protective effect of physical activity.

Table 77.1 Observational epidemiological studies on physical activity and risk of dementia or cognitive decline.

Currently, no randomized controlled trial (RCT) has ever concluded that physical activity prevents dementia or AD. Several randomized trials have reported a beneficial effect of a physical exercise programme on the cognitive performances of non-demented participants whereas other randomized trials have reported no cognitive improvement after a physical activity programme. None of these trials were designed to assess incidence of AD or dementia as the main outcome.

In 2003, Colcombe et al.,24 in a meta-analysis of 18 interventional studies with a randomized design published between 1996 and 2001, Christie concluded that there is a significant effect of aerobic exercise training on cognitive function. In a Cochrane review published in 2008, Angevaren et al.25 assessed the effectiveness of physical activity on cognitive function in people older than 55 years of age without known cognitive impairment. Eight out of 11 RCTs that compared aerobic physical activity programmes with any other intervention or no intervention reported an improvement in cognitive capacity that coincided with the increased cardiorespiratory fitness of the intervention group.

Since the above meta-analysis and systematic review, three large RCTs have reinforced these conclusions in non-demented elderly persons but also in patients with mild cognitive impairment (MCI). Patients with MCI are known to be at high risk for cognitive decline and AD and may be a target population for prevention programme.

Lautenschlager et al. reported that about 20 min per day of physical activity improved the cognitive function of 170 older adults with MCI.26 The size of the effect of 6 and 18 months of a physical programme was modest but comparable to the benefit usually reported with the use of donepezil. Other authors have also reported that a high-intensity aerobic exercise programme (75–85% of heart rate reserve for 45–60 min per day, 4 days per week for 6 months) results in an improvement of executive control processes in older women with MCI.27

Finally, in the Lifestyle Interventions and Independence for Elders pilot (LIFE-P) study, 102 older adults at risk for mobility disability were randomized to a moderate-intensity physical activity intervention during 1 year. It was reported that the improvements in cognitive scores were associated with improvements in physical function.28

Physical Activity and Executive Function

Frailty, Physical Activity and Cognitive Reserve

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