(Reuters Health) - People with dementia who exercise regularly are just as likely to experience cognitive decline as those who don't work out, a UK study suggests.
"High-intensity exercise is unlikely to cure or reduce the symptoms of dementia," said lead study author Sarah Lamb of the University of Oxford.
Researchers randomly assigned 329 people with dementia to complete four months of supervised and individual aerobic exercise and strength training workouts. They also selected a control group of 165 dementia patients at random to continue their usual care without any added physical activity.
One year later, people in the exercise group had slightly worse cognitive function than the comparison group, although the difference may be too small to be clinically meaningful, researchers report in The BMJ.
Adding exercise to usual dementia care wasn't entirely without benefit, however.
"Peoples' muscles got stronger and other aspects of their physical fitness improved," Lamb said by email.
"However, it takes the mind and body to work together to improve ability to function in everyday life," Lamb added. "In the people with dementia, it was as if the improvements in physical fitness could not translate into improvements in functions like walking around the block or climbing stairs because the mind had not improved."
An estimated 47.5 million people worldwide have dementia, and there is no cure.
Some previous experiments in animals have suggested that exercise to improve cardiovascular fitness and muscle strength and coordination might help slow cognitive impairments, but human trials to date have been too small or too brief to draw broad conclusions about any benefit for people, Lamb and colleagues write.
In the current experiment, participants were 77 years old on average and suffering from mild to moderate dementia symptoms.
Participants in the exercise group attended group workouts in a gym for 60 to 90 minutes twice weekly and were asked to complete an additional 60 minutes of home exercises each week.
One limitation of the study is that many people invited to participate declined, suggesting that exercise may not be an attractive proposition to many elderly people with dementia, the study authors note.
They might have good reason to be cautious, said Sandra Bond Chapman, director of the Center for BrainHealth at the University of Texas at Dallas.
"The most surprising finding is that physical exercise could potentially be a detriment, since the dementias progressed a little more rapidly with exercise," Chapman, who wasn't involved in the study said by email.
"I suspect that this is because the limited cognitive resources of people with dementia might be further depleted with the added burden of having to plan and do exercise," Chapman added. "This finding adds to our caution in overstating the benefits of exercise on cognitive function for those with dementia."
But they shouldn't necessarily avoid exercise altogether, said Scott Hayes, a researcher at the VA Boston Healthcare System and Boston University School of Medicine who wasn't involved in the study.
That's because the clinical impact of the cognitive decline tied to exercise in the study isn't clear, Hayes said by email.
"I think it might be premature for older adults with dementia to avoid exercise based on the results of this study alone, given the likely physical benefits," Hayes said.
For healthy older adults without dementia, there is still very good evidence that exercise incorporating a combination of aerobic and strength-building activities, preferably of at least moderate intensity, are protective against cognitive decline, noted Joe Northey of the University of Canberra in Australia.
"Although the current study didn't show benefits to cognition, physical activity as part of a healthy lifestyle is still likely to reduce the risk of other chronic diseases which can also negatively impact a dementia patients' quality of life," Northey, who wasn't involved in the study, said by email.
SOURCE: https://bit.ly/2wS5S8b The BMJ, online May 16, 2018.