By Denise Mann
WEDNESDAY, April 17 (HealthDay News) -- If Alzheimer's disease runs in your family, you may be more likely to have brain changes associated with the disorder even before symptoms such as memory and thinking problems occur, according to new research.
An estimated 5.2 million Americans have Alzheimer's disease, a number expected to increase dramatically as the baby boomer generation ages. The Alzheimer's Association predicts that the number of people aged 65 and older with the condition will reach 7.1 million by 2025.
To get a better handle on risk for Alzheimer's disease, researchers at Duke University looked at brain scans of more than 250 adults aged 55 to 89. Some had no signs of memory or thinking problems, while others did.
The researchers also analyzed genes and other markers in spinal fluid that are known to help predict Alzheimer's risk. A variation in the APOE gene was seen among those participants who were at greater risk for earlier onset of Alzheimer's.
Individuals who had a parent or sibling with Alzheimer's disease showed silent brain changes, the study found.
Specifically, close to 50 percent of healthy participants with a positive family history would have met the criteria for early Alzheimer's disease based on measurements of their cerebrospinal fluid, but just 20 percent of those without a family history would have fulfilled such criteria. The findings appear online April 17 in the journal PLoS ONE.
"In early-onset Alzheimer's disease, the genetics are much more clear-cut and we can test family members and know if they will develop Alzheimer's," said senior author Dr. P. Murali Doraiswamy, a professor of psychiatry and medicine at Duke.
It is not as clear-cut, however, when it comes to later-onset Alzheimer's, Doraiswamy said. "The genetics are much more complex, and although we know these individuals are at a slightly greater risk, we don't know when they start developing silent brain changes," he said. "[The new study is] documenting very clearly that asymptomatic family members have twice the rate of silent brain changes and that these changes happen in certain pathways known to be related to Alzheimer's disease."
The findings may help advance research that seeks to prevent Alzheimer's disease by using drugs, he said, and it's not a reason to panic and start to think the worst if you have a family history of the disease. "The findings don't suggest you should worry any more or any less," he said.
Although the study found an association between having a family history of Alzheimer's and showing brain changes related to the disease, it did not prove a cause-and-effect relationship.
"Having a family history does not mean you will get Alzheimer's disease," said Dr. Richard Isaacson, director of the Alzheimer's division at the University of Miami Miller School of Medicine. You may be at a higher risk for developing it, but it is not predestined, said Isaacson, who was not involved with the new study.
"Make brain-healthy choices now to help lower this risk," he suggested. "We know that if it is good for the heart it is good for the brain." Such choices include engaging in regular physical activity and eating a healthy low-fat diet.
"It's also important to keep your brain fit by doing something you enjoy -- whether crossword puzzles or learning a foreign language -- every day," Isaacson said.
"If you have a family history, get educated and informed about positive lifestyle choices and consider taking part in an Alzheimer's prevention trial," he said. "We can finally say 'Alzheimer's disease' and 'prevention' in the same sentence, and that is a great thing."