Could genes + neighborhood = dementia?

The long-simmering “nature” vs. “nurture” debate was settled decades ago in a draw. Biology and environment both matter.

Some ramifications are so obvious that no scientific consensus was needed: A natural athlete, given the best coaches and training, will become a star; the rest of us can practice till we drop and never make the team.

Others are harder to fathom. New research suggests, for example, that older people who live in bad neighborhoods may have poorer cognitive function — but only if they have a specific form of gene.

The work, by scientists from Drexel and Johns Hopkins Universities, builds on findings over the past decade that a variant of a gene called apolipoprotein E, or APOE, raises the risk for Alzheimer’s disease in some people. Those discoveries sparked controversy over the benefit of testing for a gene that you cannot change.
APOE is involved with brain repair. The variant known as APOE ε4 appears to interfere with that process. Mouse studies have found that adding stress — putting rats in the cage — may diminish neurological function in mice with APOE ε4. But no one had examined this connection in humans, the researchers reported in the March Archives of General Psychiatry.

The team analyzed data on 1,124 people ages 50 to 70 living in 63 Baltimore neighborhoods. The communities were ranked on a 12-item scale of “psychosocial hazards” such as violent crime, poverty, and social disorganization that could lead to long-term stress. The residents were classified by genotype.

And then they were tested on processing speed, eye-hand coordination, and other factors. People with the combination of APOE ε4 and a bad neighborhood scored worse than those with either one by itself, or with neither. Much of the difference disappeared when the researchers adjusted for demographics such as race, but some remained.

So, should people living in bad places with a bad gene move?

No, said Drexel epidemiologist Brian K. Lee, the first author. He said the findings are very early, almost theoretical.

“The most obvious thing you could do is exercise,” Lee said. Physical activity is already known to reduce dementia risk.

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