Cognitive decline among adults aged 65 years and older is a substantial public health problem in terms of incidence, health burden to the individual and care givers, as well as healthcare-related costs.1 With the world's ageing population increasing, the number of older adults with dementia is estimated to rise from 26.6 million in 2007 to 106.2 million in 2050.2

The economic burden of cognitive impairment and dementia cannot be ignored. In 2000, dementia was the third most costly health condition to care for in the USA, with annual costs estimated at $100 billion (in 1997 US prices). Another study calculated that the mean annual cost for dementia care is €28 000 per patient.3 The direct costs in the UK of Alzheimer's disease were estimated at £23 billion annually.4 Clearly, the cost of care for dementia is extremely high, and any strategies that delay the onset and/or slow the progression of cognitive decline and dementia can have enormous societal return in terms of costs and consequences. To date, effective pharmacotherapy for cognitive decline remains a challenge.1 Rather, recent evidence emphasises the importance of behavioural strategies such as physical activity to promote cognitive function.5,–,10 Specifically, results from randomised controlled trials suggest that exercise has benefits for cognitive function among cognitively normal older adults5,–,7 and among older adults with mild cognitive impairment.8 9 However, more research is needed to ascertain the direct effect of exercise on cognition among those with dementia, such as Alzheimer's disease and vascular dementia. Nevertheless, as previously highlighted by Erickson and Kramer,10 physical activity provides clear benefits for cognition among seniors. These neuroscientists contend that ‘physical activity is an inexpensive treatment that could have substantial preventive and restorative properties for cognitive and …