Advancing age increases the risk of dementia [
1], of which Alzheimer's disease (AD) is the most common cause. Available projections indicate that the number of people with dementia worldwide will increase from 35.6 million in 2010 to 115.4 million people by 2050 [
2], with dementia expected to become the major social and economic health challenge of the 21
st century.
Alzheimer's disease is characterized by a progressive deterioration in memory and other higher cortical functions that ultimately leads to a loss of independent living skills [
3]. Despite the availability of palliative medication with cholinesterase inhibitors and memantine [
4], there is currently no cure for AD. There is growing evidence that some environmental factors such as physical and cognitive activity [
5,
6], decrease the risk of AD [
7] and improve the behaviour of patients [
8], but it is unclear if such lifestyle interventions can also delay the progression of cognitive decline once the diagnosis of AD has been established [
9].
Prospective cohort studies indicate that PA is associated with reduced incidence of dementia [
10]. Middleton et al. [
11] reported that women who were physically active across the life course had a lower prevalence of cognitive impairment in later life. The association between PA and cognitive function was evident even when exercise is limited to later life [
12]. However, as Leone et al. [
13] noted, these findings are limited by methodological issues such as survivorship bias and confounding, the latter arising because the exposure to PA is not random in observational studies.
A recent randomised trial (RCT) showed that six months of PA decreased the rate of cognitive decline in older people with subjective memory complaints or Mild Cognitive Impairment (MCI) [
14], a group that is at increased risk of developing AD [
15]. Subsequently, Baker and colleagues [
16] found that six months of high-intensity aerobic activity (75-85% of heart rate reserve) improved executive control processes in sedentary women with MCI. Possible mechanisms mediating the cognitive enhancing effect of PA include alterations of cerebral vascular functioning and brain perfusion, environment enrichment and stimulation of synaptogenesis [
14]. A Cochrane review of PA trials for individuals with MCI is currently under way [
17].
Few RCTs of PA in AD have been published to date. Most evidence in this area comes from studies conducted with nursing home residents or participants with moderate to severe AD, and the primary outcomes of interest tend to be functional status and/or mood [
8,
18-
20]. The intervention provided in the largest trial, with 134 participants from five nursing homes, was a group-based multi-component exercise program [
18]. After 12 months, participants in the exercise group experienced a slower decline in their performance of activities of daily living than those in the control group, but there was no change in behavioural or psychological symptoms (BPSD). In a pilot RCT, Steinberg et al. [
19] examined the effect of a home-based, carer-supervised program of walking, strength training and balance exercises on cognition, secondary to measures of functional performance, in 27 people with AD. Although the small sample size likely precluded finding any significant differences between groups in cognitive functioning, the investigators found that the exercise program was safe, could be supervised by caregivers and had good compliance.
The objectives of the present study are to conduct a methodologically rigorous RCT investigating the potential benefits of PA on cognition, well-being, function and BPSD in community-dwelling participants diagnosed with mild to moderate AD. We will also examine whether the intervention eases stress and burden of care, an area that is often neglected in such RCTs [
21]. This paper describes the design of the Fitness for the Ageing Brain Study II (FABS II).