Obesity Tied to Brain Volume Loss

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.

Regular aerobic exercise may slow down dementia.

Regular aerobic exercise may help delay the progression of dementia in older women whose cognitive function has been affected by age, as indicated by a recent study.

A randomized controlled study tested the impact of different types of exercise on the hippocampal volume of 86 elderly women who were living independently at home but reported mild memory problems (or mild cognitive impairment [MCI]), a common risk factor for dementia. [Br J Sports Med 2013; doi: 10.1136/bjsports-2013-093184]

The women (aged 70-80) were randomized to one of three groups: the first group was assigned to a twice-weekly and hour-long exercise regime comprising aerobic training (brisk walking), the second group underwent resistance training involving lunges, squats and weights, while the third group was assigned to a balance and muscle toning exercise.

Participants were required to adhere to their respective exercise regimens over a period of 6 months. Hippocampus size was assessed at the start and the end of the 6-month period using an MRI scan, and participants’ verbal memory and learning capacity were assessed before and after using a validated test (RAVLT).

Out of the 86 women, 29 took the before and after MRI scans. The results revealed that the total volume of the hippocampus for the aerobic training group was significantly larger than the balance and muscle toning exercise group (p=0.03). There was no difference in hippocampal volume between the resistance training group and the balance and muscle toning group.

“Our study showed that aerobic training has significantly increased hippocampal volume in older women with probable MCI,” said co-author, Dr. Teresa Liu-Ambrose, Department of Physical Therapy, UBC, Vancouver, British Columbia, Canada.

The findings suggested that aerobic exercise seemed to be able to slow down the shrinkage of the hippocampus and maintain the volume in the group of women at risk of dementia at the minimum. The researchers also recommend regular aerobic exercise to stave off mild cognitive decline.

“However, more research is needed to ascertain the relevance of exercise-induced changes in hippocampal volume on memory performance in older adults with MCI,” elaborated Liu-Ambrose.

This finding is especially important as the researchers pointed out the rising toll of dementia worldwide – one new case is diagnosed every 4 seconds – and the number of those afflicted is set to rise to more than 115 million by 2050.