Genes account for 58 percent to 79 percent of a person’s risk of developing late-onset Alzheimer’s, says a study out today. That finding comes from the largest genetic study of Alzheimer’s ever done.
Late-onset Alzheimer’s, the most common form of the disease, typically strikes after age 60 and causes forgetfulness, confusion and behavioral changes. About 4.5 million people in the United States have the disease.
However, genes do not account for all of the risk of Alzheimer’s.
Study author Margaret Gatz, a professor of psychology at the University of Southern California in Los Angeles, says lifestyle factors might in some cases delay or prevent the disease, even in people who have a strong family history of Alzheimer’s.
Gatz and her colleagues studied nearly 12,000 pairs of identical and fraternal twins. The team gave all of the twins, who were age 65 and older, a battery of tests that identify memory loss, thinking problems and other signs of Alzheimer’s.
The team found 392 pairs of twins in which one or both had Alzheimer’s. The team found that Alzheimer’s disease appears highly heritable in most cases. But that does not mean automatic Alzheimer’s – it just means that people with a family history of the disease are at greater risk, Gatz says.
Some identical twins did not have the disease despite the fact that their twin did. Gatz says these identical twins, healthy at the end of the study, might never get the disease, or they might get it much later in life. The study’s findings were published in the Archives of General Psychiatry.
Although genes might play a bigger role than lifestyle choices in the development of the disease, experts such as Thomas Perls, a geriatrician at the Boston University School of Medicine, say late-onset Alzheimer’s is probably caused by an array of factors. Even people with a strong history of the disease might be able to reduce their risk or delay the onset of the disease so that they get it at age 85 instead of 70, he says.
“You can’t do anything about your family history,” adds William Thies, vice president of Medical and Scientific Affairs for the Chicago-based Alzheimer’s Association.
But Thies and Perls say people can do a lot to cut their risk by exercising, eating fruits and vegetables and staying connected socially to friends and family.