Interestingly, Alzheimer's gender differences have been discovered before. Spampinato said it's known that women have one and a half times greater risk of developing the disease, and they're believed to be more impaired in language and memory when the disease first presents itself. Women also are more prone to depression, and men to aggression, over the course of the affliction, she said.

Golf to gardening

But for men and women at risk for Alzheimer's, or who have the disease, researchers at RSNA also found some potentially heartening news: a variety of physical activities were linked with less brain volume loss, also measured using an MRI technique, in both healthy older adults and those with cognitive impairment.

This could have important implications for seniors, as the study suggests any number of aerobic activities from dancing to swimming to racquetball, might be beneficial.

"Individuals who are elderly need to be able to customize" their exercise regimens, said study author Dr. Cyrus Raji, a radiology resident at UCLA.

In his study, Raji used a technique called voxel-based morphometry to quantify gray matter. The study, which used a GE Healthcare-made 1.5-Tesla MRI scanner, was "one of the largest voxel-based imaging studies on humans ever done," he said, involving some some 876 MRI scans taken at four sites around the country, as part of a larger cardiovascular health trial.

Raji said they gave patients a survey, the Minnesota Leisure-Time Physical Activity Questionnaire, asking what physical activities they did in the previous two weeks. The researchers then estimated the amount of calories burned during the self-reported activities, and then compared brain scans of patients with their activity levels.

After controlling for a number of factors, such as age, gender, body-mass index, head size and dementia status, the researchers said they found the most active patients had 5 percent more gray matter, as measured by the scans, than the least active patients. The most active patients, who burned 3,434 kilocalories a week, had around 664 mL of gray matter, compared with the least active, who burned about 348 kilocaries a week, and had 628 mL of gray matter, he said.

Although the study doesn't show exercise caused a slowdown in gray matter loss among the most active patients, Raji said an earlier study in which patients were randomly assigned to a walking group had 2 percent greater gray matter volume in part of their brain than control patients.

Why would physical activities help? Raji said it's believed aerobic exercise can help boost blood flow to the brain and increase neurotrophic growth factors.

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