July 18, 2011 (Paris) -- Having a parent who develops Alzheimer's disease later in life is a major risk factor for the disorder. Now, preliminary research suggests that adults whose moms are affected with late-onset Alzheimer's may have an increased risk for the disease, compared with children of dads with late-onset Alzheimer's.
In the study, the children of mothers with late-onset Alzheimer's disease showed stronger evidence of Alzheimer's-like changes in the brain, as reflected on positron emission tomography (PET) imaging.
"People think that if they reach middle age and don't have memory issues, they're not going to be affected," says study researcher Megan Cummings, research coordinator for New York University's Center for Brain Health in New York City. "That's not necessarily true."
"If the findings are confirmed in larger studies, cognitively normal adults of mothers -- or even fathers -- with late-onset Alzheimer's disease might benefit from early intervention," she tells WebMD.
For now, early intervention might involve more frequent testing for dementia, but in the future, there may be drugs that slow or stop the progression from preclinical Alzheimer's disease to full-blown Alzheimer's. Preclinical Alzheimer's disease is used to describe people with signs of Alzheimer's in their brains, despite appearing cognitively normal.
Family History of Alzheimer's
The study involved 47 people in their mid-60s with no signs of cognitive decline. They were divided into three groups: those with no family history of late-onset Alzheimer's disease (no history), those with a history of late-onset disease on their father's side (paternal history), and those with a history of late-onset disease on their mother's side (maternal history).
Participants underwent two types of PET scans. One measures glucose metabolism in the brain. "The brain runs on sugar, so when it's not performing that well, glucose is being metabolized at a slower rate," Cummings says.
The other one looks for Alzheimer's-associated plaques in the brain. "If plaque is present, there is an increased risk of Alzheimer's disease and cognitive decline," she says.
The three groups were similar in terms of age, education level, scores on cognitive tests, and other factors that affect Alzheimer's risk.
The findings were presented at the Alzheimer's Association International Conference 2011.
Maternal History of Alzheimer's
The results showed a substantial reduction in glucose metabolism in the maternal history group, compared with both the paternal and the no-history groups.
Also, there was a substantial increase in the amount of plaque present in the maternal group, compared with both the paternal and the no-history groups.
"When we looked at both scans together, we found a significant correlation between the area of the brain where the plaque was and where there was a slowing of glucose metabolism," Cumming says.
Maria Carrillo, PhD, senior director of medical and scientific relations at the Alzheimer's Association, tells WebMD, "This was a small sample. Hundreds of people would have to be studied in terms of calling [maternal history of late-onset disease] a predictor."
While the researchers tried to take into account whether study participants had other risk factors for Alzheimer's, "they couldn't control for everything" that could explain the apparent link, she says, citing diabetes and heart disease as examples.
One question that the study presents, Carrillo and Cummings agree, is whether the tendency to develop dementia is somehow being passed on through mitochondrial DNA, which is only inherited from the mother.
These findings were presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.