Despite fears of Alzheimer’s, many would like to know their risk for the disease

Alzheimer’s disease can’t be prevented or cured, and it ranks second only to cancer among diseases that people fear. Still, in an international study last year from the Harvard School of Public Health, about two-thirds of respondents from the United States said they would want to know if they were destined to get the disease. Although there are no definitive tests that predict whether most people will get the disease, people sometimes want such information for legal and financial planning purposes or to help weigh the need for long-term-care insurance.

Current tests to identify the risk of developing Alzheimer’s disease when no symptoms are present provide only limited information, and health insurance generally doesn’t cover them. But that’s not stopping some people from trying to learn more.

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Most of the 5 million people who have Alzheimer’s developed it after age 60. In these cases, the disease is likely caused by a combination of genetic, lifestyle and environmental factors. About 5 percent of Alzheimer’s patients have inherited an early-onset form that is generally linked to a mutation on one of three chromosomes.

Research suggests that the brain may show signs of Alzheimer’s decades before obvious symptoms appear. Scans can identify the presence of beta-amyloid, a protein that is often deposited in the brains of people with the disease, for example. Changes in proteins in the blood or cerebrospinal fluid may also be associated with Alzheimer’s disease.

But tests to measure these changes are available only in a research setting, and insurance typically doesn’t cover them. James Cross, head of national medical policy and operations for Aetna, says his company “does not consider blood tests or brain scans medically necessary for diagnosing or assessing Alzheimer’s disease in symptomatic or asymptomatic people because the clinical value of these remains unproven.”

Genetic testing is somewhat easier to arrange, but insurers generally won’t pay for it, either.

In addition, genetic counselors caution that long-term-care insurers may use genetic testing results when evaluating whether to issue a policy. The Genetic Information Nondiscrimination Act prohibits health insurers and employers from discriminating against people based on their genetic information. However, life and long-term-care insurers are not covered by the law.

“Before anyone has genetic testing, they should get life insurance and long-term-care insurance,” says Jill Goldman, a certified genetic counselor at the Taub Institute at Columbia University Medical Center.

Genetic testing for late-onset Alzheimer’s involves one gene, the apolipoprotein E (APOE) gene on the 19th chromosome. The gene comes in three different forms — E2, E3 and E4. Everyone inherits one form, or allele, from each parent. Having one or two of the E4 variants can increase a person’s risk of developing Alzheimer’s disease three to 15 times.

About half of those who develop late-onset Alzheimer’s, however, don’t have any E4 alleles at all. Genetic testing in asymptomatic people therefore isn’t definitive or even all that informative, say experts. For late-onset Alzheimer’s, “the predictive value of genetic testing is low,” says Mary Sano, director of the Mount Sinai Alzheimer’s Disease Research Center.