Megan Brooks

November 21, 2014

Being overweight or obese is associated with poorer brain health in cognitively healthy adults in their 60s, according to new data from the long-running Australian PATH Through Life Study.

After adjustment for multiple factors, participants who were overweight or obese had smaller hippocampal volume at baseline and experienced greater hippocampal atrophy over 8 years than their normal-weight peers.

"The results further underscore the importance of reducing the rate of obesity through education, population health interventions, and policy," Nicolas Cherbuin, PhD, from the Australian National University in Canberra, Australia, said in a statement.

He reported the findings in Washington, DC, at the Society for Neuroscience 2014 Annual Meeting.

Increased Dementia

Obesity is a "major concern" and has been linked to an increased risk for dementia, Dr Cherbuin said during a media briefing. The hippocampus plays a key role in long-term memory, and hippocampal atrophy is a hallmark of cognitive decline.

Dr Cherbuin reported on 420 cognitively healthy adults aged 60 to 64 years participating in the PATH study on aging. As part of the study, body mass index (BMI) was recorded and high-resolution T1-weighted MRI was performed at study outset and then 4 and 8 years later.

At baseline, BMI was negatively correlated with left hippocampal volume (estimate per unit BMI above 25: –10.65 mm3; P = .027) and right hippocampal volume (estimate: –8.18 mm3; P = .097).

During follow-up, participants with higher BMI experienced greater atrophy in the left (P = .001) but not the right (P = .058) hippocampus, even after adjustment for age, sex, education, diabetes, hypertension, smoking, and depression.

Each 2-point increment in BMI at baseline was associated with a 7.2% decrease in left hippocampal volume during follow-up. "This is particularly significant in an aging population, and further research should be conducted to determine how obesity affects thinking abilities," Dr Cherbuin said.

"We did not investigate the relationship between shrinkage and function, but other studies in this research field have shown that greater shrinkage in the hippocampus is linked with a greater risk of cognitive decline and a greater risk of dementia as well," he said.

In an interview with Medscape Medical News, Ralph DiLeone, PhD, from Yale University in New Haven, Connecticut, who moderated the media briefing, said more information on outcomes would be of interest.

"Because the hippocampus is so important for memory function, mood regulation and is implicated in cognitive aging and dementia, it will be very interesting to see if the researchers can correlate some of those brain changes with specific behavioral deficits or disease states," he said.

The research was supported with funds from the Australian National Health and Medical Research Council, the Australian Research Council, the Dementia Collaborative Research Centre – Early Detection and Prevention, and the Australian National Computing Infrastructure. The authors have disclosed no relevant financial relationships.

Society for Neuroscience 2014 Annual Meeting. Abstract 19.04. Presented November 15, 2014.

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