May 27, 2004
Doctors now have the ability to test to see if you carry a gene that puts you at increased risk for Alzheimer's disease. But just because the technology's there, should you take the test?
It depends on many factors, experts say. And ultimately, the choice remains a personal one. All the more reason it's important to be informed about the pros and cons of Alzheimer's screening and what doctors know about genes and your risk for the disease.
"Just because genetic testing [can tell you something about your relative risk for developing] Alzheimer's disease doesn't mean it should be used in every case," writes Susanne Pavlovich-Danis, professor of nursing at the University of Phoenix, Fort Lauderdale, in a recent issue of the journal Nursing Spectrum. "Individual circumstances may determine whether test results are meaningful. What's more, test data, when interpreted inappropriately, may have devastating life-altering consequences for the patient and family members."
Genes and Alzheimer's
Alzheimer's does run in some families, most dramatically in those who carry genes known to cause an inherited early-onset form of Alzheimer's that appears at a young age. Among these are the presenilin genes, PS1 and PS2, which cause Alzheimer's to appear as early as a person's thirties or forties. Fortunately, these genes are quite rare.
Much more common is the APOE e4 gene, which increases the risk of those who carry it of developing late-onset Alzheimer's, by far the most common form of the illness. Symptoms of late-onset Alzheimer's typically arise during a person's 60s or 70s, although those who inherit two copies of the APOE e4 gene, one from each parent, are at increased risk of developing the disease even earlier. Remember, however, that "risk" does not mean you are certain or even likely to get Alzheimer's. It just means you might have a higher chance of developing the illness compared to someone without the gene.
Whether you carry the APOE e4 gene or not, many other risk factors are thought to contribute to Alzheimer's, not just genes and old age. What you eat, how much you exercise, formal education, smoking, how mentally active you remain, and other factors have all been implicated. In fact, in one recent report of elderly men and women living in Utah, more than a fourth of those who carried the APOE e4 remained Alzheimer's-free, even up to age 100.
The Perils of Genetic Testing
"Unnecessary worry or depression may develop among individuals testing positive [for APOE e4]," writes Pavlovich-Danis. "A worst case scenario would be a positive test result that contributes to suicidal behavior."
That's one reason why many experts advise against widespread testing for Alzheimer's at this time, particularly for those who remain mentally intact and show no signs of the disease. Identifying a gene that increases risk for the disease may also cause problems getting health insurance or lead to discrimination if the information were to fall into the wrong hands, Pavlovich-Danis adds.
What's more, testing can be expensive, and health insurance may not cover the cost. Even more important, there is still no effective means of preventing or curing Alzheimer's. Drugs are available, but they have only limited effectiveness in some people and do not stop the eventual downhill progression of disease.
While some people will want to have all the information they can at hand to prepare for the future, especially when Alzheimer's runs in their family, Pavlovich-Danis points out that a positive genetic test may cause other problems as well. If a forgetful older person tests positive for ApoE4, for example, he or she may be falsely given a diagnosis of Alzheimer's when other, more common causes of memory loss may be responsible for the forgetfulness. Many prescription drugs, and even over-the-counter medications, can cause symptoms that resemble those of Alzheimer's. Depression is also a common cause of memory impairment in seniorsone that is too often overlooked.
"If patients or individuals [who suspect they have] Alzheimer's [refuse] genetic testing," writes Pavlovich-Danis, "it's reassuring to share with them that 80% to 90% of patients can be correctly diagnosed based on clinical observations and simple tests," without the need for genetic testing.
Last year, the U.S. Preventive Services Task Force, a panel of experts that reviews the scientific evidence and advises the government on preventive health issues, concluded that there is not yet enough evidence to recommend that doctors routinely test all their patients for early signs of Alzheimer's disease and other forms of dementia. However, if you, family members, or caretakers are concerned about any memory problems, including memory loss or confusion, you should let your doctor know, the panel advised. Some forms of testing may be helpful, such as the MMSE (mini mental state exam), a word test for memory that is administered by a doctor.
For more on Alzheimer's testing, screening, and causes, visit www.ALZinfo.org.
Susanne J. Pavlovich-Danis, RN, professor and area chair for nursing at the University of Phoenix, Fort Lauderdale, FL. "Forecasting Forgetfulness: Screening for Alzheimer's Disease." Nursing Spectrum, May 3, 2004.
Ara S. Khachaturian, et al: "Apolipoprotein E e4 Count Affects Age at Onset of Alzheimer Disease, but Not Lifetime Susceptibility: The Cache County Study." Archives of General Psychiatry 2004;61:518-524.
Screening for Dementia: Recommendation and Rationale. U.S. PREVENTIVE SERVICES TASK FORCE. American Family Physician, March 15, 2004.