Dr. David Bennett and his colleagues at Rush University Medical Center in Chicago autopsied the brains of 89 people who had participated in regular mental tests and been questioned about their network of friends and relatives.

Many people whose brains had Alzheimer-related abnormalities called plaques and tangles did not actually show any signs of dementia when they were alive. These people also tended to have larger social networks.

Bennett says the results suggest social interaction does not prevent the development of brain abnormalities, but it allows people to cope with those changes once they develop.

"There's something different about the brains of people who have large social networks, or there's something different about the brains of people who are able to form large networks."

He says these people may be able to tap into brain systems involved in maintaining social skills and use them to help preserve their memory abilities when those parts of the brain begin to fail.

So far, the only practical implications of this research are "the usual general platitudes of keep yourself engaged cognitively, physically, socially," Bennett says.

"The other message is that Alzheimer's disease is modifiable. It probably will be modifiable. And it may not be a pill. It may be a lifestyle, just like a lot of other things are. And I think it should give us hope that we're beginning to really increase our understanding of how this disease works and manifests itself.

"It's not inevitable either," he adds. "It's not a normal part of aging."

With files from The Medical Post.