Perhaps no part of the aging process is more feared than losing one’s cognitive abilities. And it’s a growing concern.

In the United States, one in three seniors dies with Alzheimer’s or another dementia syndrome, according to a new report from the Alzheimer’s Association. The March 2013 report shows that while deaths from other major diseases, such as heart disease, HIV/AIDS and stroke, continue to experience significant declines, Alzheimer’s deaths continue to rise — increasing 68 percent from 2000 to 2010.

Yet there may be hope on the horizon: A growing number of studies indicate the potential for exercise to delay the onset of cognitive diseases like Alzheimer’s.

“It is generally accepted that regular physical activity is essential to healthy aging,” says Dr. Heather Snyder, director of medical and scientific operations of the Alzheimer’s Association, based in Chicago.

“With further research, it also may prove to be a strategy to delay or prevent the onset of cognitive impairment and dementia,” she says. There is strong evidence that physical activity can reduce risk of Alzheimer’s disease currently, but the results are preliminary and more long-term studies are needed to provide more information, Snyder says, such as “exactly which types of physical activity are most effective, how much needs to be done and for how long.”

In particular, Snyder cited four studies reported at the 2012 Alzheimer’s Association International Conference that describe the ability of targeted exercise training to promote improved mental functioning and reduced risk for cognitive impairment and dementia in cognitively healthy older adults and those with mild cognitive impairment.

The reports, from 6- and 12-month randomized controlled clinical trials, depict the beneficial effects of different types of exercise – resistance training, aerobic training, and balance-stretching training – on a variety of cognitive abilities, brain structure, functional neural plasticity, growth factors and risk factors for cognitive decline, such as depression and sleep quality.

More research needs to be done, Snyder says, before a “prescription” can be made for certain types of physical activity, for certain periods of time, at certain levels of intensity to reduce Alzheimer’s risk. That does not exist yet, but the field is asking these same types of questions and scientists are working toward this type of understanding.

At the same time, evidence suggests exercise may directly benefit brain cells by increasing blood and oxygen flow to the brain.

“When we exercise, 25 percent of our blood goes to the brain,” says Dr. Paul Nussbaum, chair of the prevention board at the Alzheimer’s Foundation of America in New York. “When people exercise, what they are really doing is helping their brain.”

Some of the latest research, Nussbaum says, indicates the types of exercise that may benefit the brain.

“A lot of it is aerobic in nature,” Nussbaum says. “Twenty minutes… of aerobic exercise, like treadmills and dance.”

Gardening has been shown to benefit the brain in cognitive studies, Nussbaum adds.

Growing evidence shows that physical activity does not have to be strenuous or even require a major time commitment, Snyder points out.

“It is most effective when done regularly and in combination with a brain-healthy diet, mental activity and social interaction,” Snyder says. “Aerobic exercise improves oxygen consumption, which benefits brain function; aerobic fitness has been found to reduce brain cell loss in elderly subjects.”