Winter 2008
Are You at Risk of Developing Alzheimer’s?

Genetic testing may provide an answer – but it’s rarely decisive and can have unexpected consequences


People with a family history of Alzheimer’s disease may consider genetic testing to find out if they are at risk. But experts say the tests are only useful in certain circumstances, and they raise a host of thorny personal and legal issues.

Two types of genetic tests exist for Alzheimer’s. A predictive test determines whether an unaffected person has a very high chance of developing the disease, but is useful for only the small number of people who carry a genetic mutation causing the early-onset form. (At least 90 per cent of Alzheimer’s cases are late onset and not clearly hereditary, so a negative test result doesn’t rule out the possibility of developing the disease.)

Another test, known as genetic risk assessment, indicates if someone has a somewhat greater likelihood of developing Alzheimer’s, but it can’t predict with any certainty who will or will not develop the disease. Because the test is not predictive, it’s not offered as a clinical service in Canada.

People considering genetic testing for Alzheimer’s will want to think carefully about how a positive result could affect them – and family members – psychologically, since there is no long-term effective treatment or cure.They may also want to think twice before stepping into a legal grey zone, says Trudo Lemmens, a U of T law professor and coauthor of the book Reading the Future? Legal and Ethical Challenges of Predictive Genetic Testing. Lemmens says the law is still unclear, for example, about who can use the information from a genetic test and for what purpose. Should insurance companies be able to screen people on the basis of a genetic test? What about adoption agencies and employers? “Risk of early death is certainly information that would be interesting to some of these groups,” he says.

As the tests become cheaper to conduct, Lemmens says insurance companies could use genetic information to deny coverage or charge higher premiums to individuals with an increased risk of developing a life-threatening disease. In theory, employers could use it to exclude employees with undesirable traits from the workplace, and adoption agencies could use it to rule out some prospective parents.

On the other hand, there are situations in which the genetic test results could prove beneficial. For people who have a family history of Alzheimer’s, a negative result could yield a reduction in insurance premiums. (These people normally pay higher premiums, since insurance companies already use family medical history to assess an individual’s health risks.)

To guard against the misuse of genetic information, the law should regulate who can conduct genetic testing and for what purpose, says Lemmens. “This is a fundamentally personal decision. We don’t want people to be forced to undergo genetic testing for employment or insurance purposes, for example, and to know something they didn’t want to know.”


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