The study adds to a growing body of evidence that a tendency for the disease appears to be passed down through the mother's genes. Previous studies have found that people who have a close relative — mother, father, brother, sister — with the disease are four to 10 times more likely to develop Alzheimer's compared with those who have no direct family history.
Experts say the research may one day lead to gene manipulation that could prevent the disease. For now, though, it should encourage those with a family history of Alzheimer's to eat healthy foods and exercise, two strategies linked to a lower risk of the disease.
For this study, researchers at the University of Kansas followed 53 healthy men and women age 60 and over for two years. Eleven of them had a mother with Alzheimer's disease, 10 had a father with the disease and 32 had no family history. The groups were given brain scans and memory tests throughout the study.
The researchers found that people with a mother who had Alzheimer's disease had twice as much brain shrinkage as those who had a father — or no parent — with the disease. Men and women who had a mother with Alzheimer's had about one and a half times the shrinkage as those with a father with the disease. Brain shrinkage is one of the key early signs of the disease. Robyn Honea, lead author of the study and assistant professor of neurology at the University of Kansas School of Medicine, says none of the subjects developed the disease during the study.
Today, more than 5 million Americans have Alzheimer's, and yet there is no proven treatment or cure.
"The more you know about what makes you at risk, the more helpless you feel," says Honea. But having a mother with Alzheimer's "doesn't mean that you will get the disease." She adds that a complex interplay of nature and nurture appears to be involved in the development of the disease.
Lisa Mosconi, assistant professor of psychiatry at the Center for Brain Health at NYU Langone Medical Center, said the study is the first to follow healthy subjects and use MRI brain imaging to track changes in the brain over time, and it strengthens the evidence of a maternal link to the disease. Mosconi was not involved in this study but has conducted previous research that found people who had mothers with the disease showed more signs of brain atrophy than those who had fathers with the disease or no family history.
Meanwhile, both researchers are following their subjects to see which men and women develop Alzheimer's and — perhaps most importantly — to see what they can learn from those who don't. One theory as to the link between mothers and children and Alzheimer's is that some trigger is carried through genetic material that is only passed through mothers.
Mosconi admits that it's hard to be patient. She says her own grandmother recently died from the disease, and she worries for her own mother. But she and other scientists say there is real reason to hope as companies and researchers work feverishly to find drugs that will prevent or slow the progression of the disease.
"It's only a matter of time. It's not like we'll never have a cure," Mosconi says. "I would say, hopefully, within a few years there will be something that's really effective against the disease."
Elizabeth Agnvall is a contributing editor with the AARP Bulletin.