A randomized controlled trial has found that moderate- to high-intensity aerobics and strength training do not slow cognitive decline any better than usual care in mild to moderate dementia. Results also suggested a possibly increased cognitive impairment with the type of exercise regimen used in the study. Although the reasons are unclear, the authors suggest different types of exercise may have different impacts on cognitive functioning in dementia.
“Moderate to high intensity aerobic and strength exercise cannot be recommended as a treatment option for cognitive impairment in dementia,” wrote first author Sarah Lamb, DPhil, of the University of Oxford (Oxford, UK) and colleagues with the Dementia and Physical Activity Trial investigators. “Investigators should consider the possibility that some types of exercise intervention might worsen cognitive impairment and of a “rebound” effect if the exposure to an intervention is to be time limited,” they added.
The study was commissioned by the National Institutes for Health Research (NIHR) in the UK, in response to a 2012 challenge by the British prime minister to prioritize research on treatments and cures for dementia. The aim of the study was to see if aerobic and strength training can successfully slow cognitive decline, in preparation for use in the UK National Health Service. Few large randomized controlled trials (RCTs) have evaluated the issue.
To provide better evidence, researchers conducted an RCT in individuals recruited from a wide range of clinical practices in 15 English regions. The trial included 494 individuals with mild to moderate dementia, 329 of whom were randomized to the intervention and 165 to usual care. The average age of participants was 77 years, and 61% were men. The intervention was designed to target known mechanistic pathways in vascular and Alzheimer disease (AD). It consisted of 4 months’ supervised group exercise classes, which included high intensity cycling and strength training using weights for the upper and lower limbs. The primary outcome was 12-month score on the Alzheimer’s disease assessment scale-cognitive subscale (ADAS-cog), which is scored from zero to 70 with higher scores indicating worse cognitive impairment.
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They offered several explanations that might explain these results. Ending the group classes could have caused a withdrawal effect related to social and emotional factors, which could have affected cognition. Biological mechanisms could also have been involved. Studies in healthy individuals have suggested that high intensity exercise training may slow reoxygenation of areas of the brain involved in executive functioning. Exercise can also increase levels of inflammation.
“Future trials should explore other forms of exercise, including psychomotor protocols that are commonly used in long term neurological conditions where the primary intent is improving physical functioning.” –Lamb and colleagues
Take home points -English RCT found 4 months of group classes with aerobic and strength training improved physical fitness but not cognitive decline vs usual care in mild to moderate dementia -The intervention was linked to increased cognitive decline vs usual care; clinical relevance uncertain -The intervention was not linked to improvements in other clinical factors, and resulted in higher rates of adverse events vs usual care -Other forms of exercise may need to be considered in mild to moderate dementia