People can do a lot to cut their risk of Alzheimer's disease by exercising, eating fruits and vegetables, and staying connected to friends and family.

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 US 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, such as maintaining social ties, might in some cases delay or prevent the disease even in people who have a strong family history of the disease.

Identical Twins Studied

Gatz and her colleagues studied nearly 12,000 pairs of identical and fraternal twins from Sweden. The team gave all of the twins, who were ages 65 and older, a battery of tests that identify memory loss, cognitive 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 automatically mean Alzheimer's -- it just means that people with a family history of the disease are at greater risk, Gatz says.

Even identical twins, who share the same genetic material, do not always get the disease in lock step, she says. Some identical twins did not have the disease despite the fact that their twins did.

Gatz says these identical twins, who were healthy at the end of the study, might never get the disease, or they might develop it much later in life. The study's findings were published in the Archives of General Psychiatry.

Exercise, Fruits and Veggies, Friends and Family

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 a complex disease probably caused by an array of factors.

That means even people with a strong history of the disease might be able to reduce their risk or delay the onset of the disease so they develop it at age 85 and not at 70, he says.

"You can't do anything about your family history," says 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 to friends and family.

Other research has suggested that healthful living might help reduce the risk of developing the disease. "These findings should be regarded as a warning: If you have Alzheimer's in the family, you have to take precautions," Perls says.