Brain Changes Leading to Alzheimer's More Likely Inherited from Mother
People who have first-degree relatives with Alzheimer’s disease are as much as ten times more likely to develop the disease themselves compared to those with no family history. A new study from researchers at the University of Kansas School of Medicine find that the risk of inheriting Alzheimer’s is greater if the mother has the disease versus the father.
Excessive Brain Atrophy is Early Alzheimer's Symptom
For the study, Robyn Honea DPhil and team followed 53 dementia-free people aged 60 and older for two years. Eleven of the participants had a mother with Alzheimer’s and 10 had a father with the neurodegenerative disease. Thirty-two of the volunteers had no family history of Alzheimer’s. The subjects were given brain MRI scans and tests to measure memory, language and cognitive skills throughout the study.
“Using 3-D mapping methods, we were able to look at the different regions of the brain affected in people with maternal or paternal ties to Alzheimer’s disease,” said Honea. Brain atrophy is normal with aging, but accelerated shrinkage is considered an early sign of Alzheimer’s disease.
The researchers found that people whose mother had Alzheimer’s had twice as much brain gray matter shrinkage in the parahippocampal gyrus and the precuneus, two areas known to be affected by Alzheimer’s. In addition, those patients also had about one and half times more whole brain shrinkage per year compared to the people who had a father with the disease.
Although 63% of those with a maternal family history of Alzheimer’s carried the ApoE4 gene, the findings held true even when accounting for this high risk factor.
However, in all groups, the performance on the cognitive tests did not change from baseline at the end of the two year study, suggesting that the brain atrophy had not yet impaired memory.
Dr. Honea, an assistant professor of neurology, hypothesizes that a dysfunction in mitochondrial DNA, which is only passed through the mother, affects certain processes that lead to brain changes in those with a maternal history of the disease.
Maria Carrillo PhD, the senior director of medical and scientific relations for the Alzheimer’s Association, notes that although the findings are consistent with previous studies on the maternal influence of Alzheimer’s risk, the study sample was too small to accurately draw a conclusion.
The authors also acknowledge that the study depended on volunteers reporting their parents’ illnesses accurately.
About 5.3 million Americans have Alzheimer’s disease and that number is expected to grow substantially over the next 20 years as the Baby Boomer generation reaches 65 and older.
Robyn A. Honea, Russell H. Swerdlow, Eric D. Vidoni and Jeffrey M. Burns. Progressive regional atrophy in normal adults with a maternal history of Alzheimer disease. Neurology, March 1, 2011 vol. 76 no. 9 822-829 DOI: 10.1212/WNL.0b013e31820e7b74