Hidden abdominal fat in midlife may raise Alzheimer’s risk later: Study

New York: Higher amounts of visceral abdominal fat in midlife can raise the risk of Alzheimer's disease, according to research.

Visceral fat is fat surrounding the internal organs deep in the belly. Researchers found that this hidden abdominal fat is related to changes in the brain up to 15 years before the earliest memory loss symptoms of Alzheimer's disease occur.

To identify Alzheimer's risks earlier, researchers assessed the association between brain MRI volumes, as well as amyloid and tau uptake on positron emission tomography (PET) scans, with body mass index (BMI), obesity, insulin resistance and abdominal adipose (fatty) tissue in a cognitively normal midlife population.

Amyloid and tau are proteins thought to interfere with the communication between brain cells.

"Even though there have been other studies linking BMI with brain atrophy or even a higher dementia risk, no prior study has linked a specific type of fat to the actual Alzheimer's disease protein in cognitively normal people," said Mahsa Dolatshahi, post-doctoral research fellow with Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis.

"Similar studies have not investigated the differential role of visceral and subcutaneous fat, especially in terms of Alzheimer's amyloid pathology, as early as midlife," Dr. Dolatshahi said.

For this cross-sectional study, researchers analysed data from 54 cognitively healthy participants, ranging in age from 40 to 60 years old, with an average BMI of 32.

The participants underwent glucose and insulin measurements, as well as glucose tolerance tests. The volume of subcutaneous fat (fat under the skin) and visceral fat were measured using abdominal MRI.

Brain MRI measures the cortical thickness of brain regions that are affected in Alzheimer's disease. PET was used to examine disease pathology in a subset of 32 participants, focusing on amyloid plaques and tau tangles that accumulate in Alzheimer's disease.

The researchers found that a higher visceral to subcutaneous fat ratio was associated with higher amyloid PET tracer uptake in the precuneus cortex, the region known to be affected early by amyloid pathology in Alzheimer's disease. This relationship was worse in men than in women.

The researchers also found that higher visceral fat measurements are related to an increased burden of inflammation in the brain.

The results may point to visceral fat as a treatment target to modify risk of future brain inflammation and dementia.

The findings will be presented next week at the annual meeting of the Radiological Society of North America (RSNA).