Gene raises Alzheimer's risk, but testing for it doesn't raise anxiety

— -- Adult children of Alzheimer's disease patients don't suffer psychological distress when told they carry a gene that increases their risk of the disease, researchers report Thursday.

Increasingly, companies are marketing tests directly to consumers that promise to reveal their genetic susceptibility to killers such as heart disease, diabetes and Alzheimer's.

Because the tests are virtually unregulated, concerns have been raised about their accuracy as well as their value. While people can take steps to protect against heart disease or diabetes, there's no known effective way to minimize Alzheimer's risk.

The only known genetic risk factor for late-onset Alzheimer's, which begins after age 60, is the apolipoprotein E, or apoE, gene.

There are three main apoE types: 2, 3 and 4. The new study is the first to randomly tell people their apoE types, the authors write in The New England Journal of Medicine. Up to two-thirds of Americans inherited two copies of apoE3, which doesn't seem to affect Alzheimer's risk. ApoE2 appears to be somewhat protective, while apoE4, carried by at least one in five, raises the risk.

People who inherit apoE4 from both parents are at least five times more likely to develop Alzheimer's than those who don't carry a copy. Another study in this week's New England Journal found that healthy apoE4 carriers also are likely to begin experiencing age-related memory decline sooner than non-carriers.

"People were very, very nervous essentially about the danger of this information, so much so they thought you shouldn't give it," says Lawrence Brody, a senior scientist at the National Human Genome Institute, who wasn't involved in either study.

But lead author Robert Green, a Boston University professor of neurology, genetics and epidemiology, says many want to know their apoE status. "We're testing a procedure that we think allows them to learn this information with safety," Green says.

His study of 162 volunteers found that those who were told they carried apoE4 were no more anxious or depressed than those who weren't told their test results. Anxiety and depression were reduced in those who learned they don't carry apoE4.