Does knowing your genetic risks lead to better health?

Will genome scan services improve people’s health -- or not? So far, the limited evidence on behaviors after genetic testing has yielded mixed results.

For example, a 1997 study on 426 smokers conducted at Georgetown University Medical Center found that giving smokers information on their genetic risk of lung cancer upped the motivation to quit -- but a year afterward they were no more likely to have quit smoking than people who received more general counseling.

One reason for this lack of effect may be that people just don’t understand their genetic risks. A 2004 study out of Duke University Medical Center found that six months after testing, 36% of smokers inaccurately remembered their genetic test results, and 45% misinterpreted the results.

Another intriguing study is by Dr. Robert Green, professor of neurology, genetics and epidemiology at Boston University School of Medicine, and colleagues, on about 500 people who were tested for Alzheimer’s disease risk. All had relatives already diagnosed with the condition.

The subjects, who received detailed information and counseling, understood their results, showed no lasting anxiety or depression and didn’t regret taking the test -- even if they’d tested positive for APOE4, the variant of the APOE gene (the same one I have) that puts them at higher risk for Alzheimer’s.

“They understand . . . it’s not going to tell them definitively that they are going to get this disease or not. Yet they have remarkably high satisfaction with having gone through the experience,” Green says.

Another paper from Green’s group found that those who tested positive for APOE4 were more likely, one year after the test, to have adopted a new healthful habit aimed specifically at warding off the disease -- although there are no proven methods for preventing Alzheimer’s, a fact that researchers made clear to the study participants.

The behaviors included exercising and taking multivitamins and other medications, most likely cholesterol-lowering statins, Green says. Those who tested positive also started purchasing more long-term care insurance -- a finding sure to set insurance companies quaking in their boots.

So complex genetic information can be understandable, but not always. It doesn’t seem to help smokers kick a habit they know is very bad, yet can persuade people at risk for Alzheimer’s to adopt behaviors that are healthful in general but may do nothing to ward off the disease. Which may not be a resounding endorsement of the effectiveness of genetic testing, but does, perhaps, suggest promise.

-- Anna Gosline