New research hints that even a simple exercise routine just might help older Americans with mild memory problems.

Doctors have long advised physical activity to help keep a healthy brain fit. But the government-funded study marks the longest test of whether exercise makes any difference once memory starts to slide — research performed amid a pandemic that added isolation to the list of risks to participants’ brain health.

Researchers recruited about 300 sedentary older adults with hard-to-spot memory changes called mild cognitive impairment or MCI — a condition that’s sometimes, but not always, a precursor to Alzheimer’s. Half were assigned aerobic exercises and the rest stretching and balance moves that only modestly raised their heart rate.

Another key component: Participants in both groups were showered with attention by trainers who worked with them at YMCAs around the country — and when COVID-19 shut down gyms, helped them keep moving at home via video calls.

After a year, cognitive testing showed overall neither group had worsened, said lead researcher Laura Baker, a neuroscientist at Wake Forest School of Medicine. Nor did brain scans show the shrinkage that accompanies worsening memory problems, she said.

By comparison, similar MCI patients in another long-term study of brain health — but without exercise — experienced significant cognitive decline over a year.

Those early findings are surprising, and the National Institute on Aging said tracking non-exercisers in the same study would have offered better proof.

But the results suggest “this is doable for everybody” — not just seniors healthy enough to work up a hard sweat, said Baker, who presented the data Tuesday at the Alzheimer’s Association International Conference. “Exercise needs to be part of the prevention strategies” for at-risk seniors.

Previous research has found regular physical activity of any sort may reduce damaging inflammation and increase blood flow to the brain, Alzheimer’s Association chief scientific officer Maria Carrillo said.