Mapping Study Suggests Brain Shrinkage in Obese Elderly could Increase Alzheimer's Risk

Elderly people who are overweight or obese tend to have less tissue in certain areas of the brain, suggesting they might be at greater risk for dementia, Alzheimer's disease, and other cognition-impairing disorders, according to recent research.

The study, conducted by investigators from the University of Pittsburgh (Pitt; PA, USA) and the University of California, Los Angeles (UCLA; USA), was based on data collected from structural magnetic resonance imaging (MRI) brain scans conducted for the Pittsburgh (PA, USA)-based Cardiovascular Health Study. The researchers discovered that people age 70 or older and overweight, meaning with a body mass index from 25-30, had 4% less tissue in the frontal lobes of the brain than their normal-weight peers. Those who were obese, with a body mass index (BMI) greater than 30, had 8% less tissue in the same regions, which are crucial for cognitive tasks such as memory and planning, according to lead investigator Cyrus A. Raji, Ph.D., who is in the combined M.D./Ph.D. program at Pitt's School of Medicine.

"It seems that along with increased risk for health problems, such as type 2 diabetes and heart disease, obesity is bad for your brain. We have linked it to shrinkage of brain areas that also are targeted by Alzheimer's,” Dr. Raji said. "But that could mean exercising, eating right, and keeping weight under control can maintain brain health with aging and potentially lower the risk for Alzheimer's and other dementias.”

The 94 participants in the study, which was published in August 2009 in the online version of the journal Human Brain Mapping, were all cognitively normal at the time their brain imaging was performed and five years later. New, advanced methods of computer analysis were applied to the high-resolution scans, allowing three-dimensional (3D) mapping of brain structures to reveal patterns in volume differences that were not apparent in previous research.

The investigators found that the people defined as obese had lost brain tissue in the frontal and temporal lobes, areas of the brain critical for planning and memory, and in the anterior cingulate gyrus (attention and executive functions), hippocampus (long term memory), and basal ganglia (movement). Overweight individuals showed brain loss in the basal ganglia, the corona radiata, white matter comprised of axons, and the parietal lobe (sensory lobe).

"This is the first time anyone has created brain maps proving the link between being overweight and severe brain degeneration,” said senior investigator Paul M. Thompson, Ph.D., professor, department of neurology, UCLA School of Medicine. "The brains of obese people looked 16 years older than the brains of those who were lean, and the brains of overweight people looked eight years older.”

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