There are currently no treatments that effectively prevent, cure, or slow progression of dementia, leaving an estimated 47.5 million dementia patients – and their families – in dire need. Following a string of disappointing drug development failures, many research groups have optimistically championed exercise as an alternate intervention, based on the well-established link between physical activity and improved cognitive function.
However, many of these investigations have been done in mice, feature small groups of people, or are retrospective in nature – looking backward at the lifestyle factors of people who already have dementia and comparing them to those who do not.
Randomized control trials (RCT) with a large number of participants – the gold standard of scientific evidence – have so far been lacking.
To fill this gap, a team from the Universities of Oxford and Warwick conducted an ambitious RCT that assigned 329 subjects with mild to moderate dementia, living across the UK, to a four-month-long moderate to high intensity aerobic and strength training program consisting of two instructor-led 60- to 90-minute gym sessions and one hour of exercise at home each week. Then, for eight additional months, caregivers were told to supervise a home-based program of 150 minutes of exercise each week.
A control group of 165 patients was assigned to standard care that included brief advice on physical activity.
Sadly, after 12 months, patients in both groups showed cognitive decline characteristic of the disease. Those in the exercise group actually had worse cognitive impairment, yet the difference was too small for the team to make any sweeping conclusions.
“The exercise improved physical fitness in the short term, but this did not translate into improvements in activities of daily living, behavioural outcomes, or health-related quality of life,” they wrote in the British Medical Journal. “There is the possibility that the intervention could worsen cognition.”
These findings appear to have split the dementia specialist community – some appear resigned to accept that although regular exercise earlier in life might protect against dementia, it cannot help patients who have already developed symptoms stemming from brain changes that occurred many years previously. Yet, others argue that further studies should be conducted before we rule out the benefit of exercise as medicine.
"Whilst previous smaller studies have suggested that exercise can prevent or improve cognitive decline in people with Alzheimer’s disease, this robust and very large study provides the most definitive answer we have on the role of exercise in mild-moderate Alzheimer’s disease,” Dr Brendan Stubbs of King’s College Institute of Psychiatry, Psychology and Neuroscience told the Science Media Centre. “The search for effective lifestyle interventions that can delay cognitive decline in dementia must continue.”
“The results are somewhat surprising as we would anticipate that exercise would have positive effects," added Dr James Pickett, head of research and development at Alzheimer’s Society. "We want to see more investment in this avenue of research before we assume categorically that exercise is non-beneficial for cognitive function.”