December 23, 2009
Would you want to know your risk for Alzheimer's disease? That is a long-simmering debate in the Alzheimer's field, as new genetic tests make it possible to learn if you carry a gene that make you susceptible to developing severe memory loss and problems with thinking in old age.
But results from a trial, known as the Risk Evaluation and Education for Alzheimer's Disease, or REVEAL, study found that when people learn that they carry the gene, they do not experience prolonged bouts of mental distress. Any depression or anxiety that ensues, the researchers found, was not long lasting. The findings were published in The New England Journal of Medicine.
The gene in question, called APOE-E4, does not guarantee that you will get the late-onset form of Alzheimer's disease, the most common form of the disorder. But it does increase your risk of developing the disease. Those who inherit one copy of the gene from a parent are at three- to five-fold increased risk of developing Alzheimer's compared to those who don't carry the gene. And those who carry two copies of the gene are at 15-fold risk of developing Alzheimer's.
Some experts say it is better not to test for this Alzheimer's gene, as the test is not definitive and only tells you that you may be at increased risk for developing the disease. Furthermore, there are no effective treatments for halting the downward progression of disease, and getting the test, they argue, will only lead to heightened stress and anxiety.
The scientists studied 162 men and women who had a parent with Alzheimer's. The researchers provided educational sessions about Alzheimer's risk and genetic factors. About 80 percent of the study participants wanted to have the genetic test for the APOE-E4 gene, while 20 percent declined. For those who agreed to a genetic test, counselors disclosed results and followed participants for a year.
They found that at six weeks, those who had learned they carried the APOE-E4 gene showed some signs of distress. But anxiety, depression and stress levels were not heightened after six months or a year.
"Some people might say, 'I'm thinking about this a lot,' but it didn't translate into long-term depression or anxiety," said co-author Scott Roberts, now a researcher at the University of Michigan School of Public Health. "The findings show if you do (disclose this genetic information) genetic counseling may be an important component to ensure that most people do not respond with significant distress."
"Genetic counselors help put the test results in context so that people understand the meaning and limits of the results," Dr. Roberts added. For example, participants who carried that gene might have a 55 percent lifetime risk of developing Alzheimer's. But counselors explained that there was a 45 percent chance that they would never develop the disease.
Scientists have known since the 1990s that the APOE gene was linked to Alzheimer's risk. And for much of that time, the medical community has argued against testing for the gene or similar genetic markers. But a growing number of private companies offer genetic testing of varying types, and some argue that it should be a patient's right to decide if he or she wants to learn test results.
Doctors say that the current study was relatively small, and that participants were only followed for a year. It is possible that distress may increase with advancing age. Study participants were also provided with extensive counseling from genetic experts, which likely helped to minimize stress. Such extensive counseling may not be readily available in many medical settings.
Robert C. Green, M.D., M.P.H., J. Scott Roberts, Ph.D., L. Adrienne Cupples, Ph.D., et al: "Disclosure of APOE Genotype for Risk of Alzheimer's Disease," New England Journal of Medicine, Volume 361, pages 245-254.