Specifically, exercisers saw improvements in their executive function — the brain‘s ability to pay attention, regulate behavior, get organized and achieve goals. And those who also made some healthy diet changes, including eating more fruits and vegetables, showed somewhat bigger gains.
The effect was equivalent to shaving about nine years from their brain age, said lead researcher James Blumenthal, a professor at Duke University School of Medicine, in Durham, N.C.
In contrast, those same mental abilities kept declining among study participants who received health education only.
Experts said the findings support the general concept that a healthy lifestyle can help protect the brain as you age.
“And it’s never too late to start,” said Keith Fargo, director of scientific programs and outreach for the Alzheimer’s Association. “The people in this study were older, already had cognitive [mental] impairments and cardiovascular risk factors, and they were sedentary.”
Fargo, who was not involved in the research, described the findings as “great news.”
He said that’s in large part because this was a clinical trial that actually put exercise to the test. Many past studies have found that physically active people tend to be in better mental shape as they age. But those studies don’t prove cause and effect, Fargo noted. Clinical trials do.
Blumenthal echoed the “never too late” message, and also said the exercise routine used in the trial was very accessible. People walked or rode a stationary bike three times a week, for 35 minutes with a 10-minute warmup.
“They weren’t training for a marathon,” he added.
Blumenthal said the same of the diet changes some study participants made. They followed the so-called DASH diet, which is routinely recommended for people with high blood pressure. It is rich in fruits, vegetables, whole grains and healthy unsaturated fats, and low in sodium, sugar, and meat and dairy high in saturated fat.
Fargo agreed that those changes are within reach for most older adults. “Almost everyone can get up and sweat a few times a week,” he said. “Almost everyone can eat more fruits and vegetables than they already do.”
For the study, Blumenthal’s team recruited 160 adults, aged 55 and older, who had complaints about their memory and thinking abilities. Objective tests confirmed that they had signs of impairment.
None had full-blown dementia, such as Alzheimer’s disease. But at the outset, the group’s performance on tests of executive function was similar to that of people in their early 90s — even though their real average age was about 65.
Participants were randomly assigned to one of four groups: one that exercised; one that followed the DASH diet; one that exercised and made the diet switch; and another that received health education only.
After six months, both exercise groups showed improvements in tests of executive function, while the health-education group continued to decline. People who exercised and followed the DASH diet seemed to fare best — but the diet alone did not make a statistically significant difference.
Blumenthal stressed that the study group was small, which makes it more difficult to tease out the effects of each intervention. He said larger studies are still needed.
It’s also unclear whether exercise and diet can ultimately delay or prevent full-blown dementia in some people.
Why would exercise and a healthy diet help with thinking skills?
It’s not clear, Blumenthal said. But in this study, there was a correlation between improvements in physical fitness and people’s test performance. Similarly, if their heart disease risk factors improved — a drop in blood pressure, for example — their test scores rose, too.
According to Fargo, that’s consistent with the theory that a healthier flow of blood and oxygen to the brain may boost older adults’ mental acuity.
He noted that the Alzheimer’s Association is launching a trial that will test a combination of lifestyle changes — exercise and diet, plus social engagement and mentally stimulating activities such as puzzles and crosswords.
It will look at whether those measures can protect mental function in older adults at increased risk of decline.
The study was published online Dec. 19 in the journal Neurology.
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