updated 6/19/2005 7:03:56 PM ET 2005-06-19T23:03:56

Education and a healthy youth may override genes in determining who gets Alzheimer’s disease, says a provocative new study of dementia patients and their healthy identical twins.

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Researchers combed Sweden’s twin registry to find 109 identical twins where one had Alzheimer’s or another form of dementia but the other remained healthy. Then they checked the twins’ medical histories.

Having had a stroke increased the chances of dementia six-fold, not surprising as cardiovascular disease has long been considered a risk factor, scientists reported at an Alzheimer’s Association conference on the quest to prevent the disease.

More surprising were two early-in-life factors:

  • Twins who had had early periodontal disease — leading to loose or lost teeth by age 35 — had a fourfold increased risk of dementia. Gum disease is a sign of poor child health in general. It’s also an inflammatory disease; inflammation increases the risks of numerous disorders later in life.
  • Those with less high school and college education had 1.6 times the risk of dementia. Mental stimulation throughout life is thought to be brain-protective.

“I’d thought at first the story would be in the genes,” said lead researcher Dr. Margaret Gatz of the University of Southern California, who was surprised to find education’s role.

In interviews, surviving twins spoke about how a sibling was never as interested in school or struggled with it. Gatz immediately wondered if childhood infections played some role in their early brain development, which led to the gum disease finding. Now she’s exploring other factors.

The bottom line: “Good brain health ... in old age reflects influences that begin much earlier in the life span,” she said.

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