(CN) — Tens of millions of people around the world live with Alzheimer's disease, and millions more of their friends and families are affected by its impact on their minds and bodies. Scientists don’t exactly know why people get the disease, but new research suggests that higher amounts of visceral belly fat in middle-aged people is linked to the development of Alzheimer’s disease.
Alzheimer's is a progressive neurodegenerative disease that first affects people’s short term memory, and then gradually affects their long term memory, language ability, and mobility. According to the Alzheimer’s Association, an Alzheimer's care, support and research organization, one in three American seniors dies with the disease, or another form of dementia. More than 6 million Americans have the disease. By 2050, 13 million Americans — one in every five women and one out of 10 men — are projected to develop the disease in their lifetime.
The Centers for Disease Control and Prevention lists Alzheimer’s disease as the seventh leading cause of death for Americans, killing more than 119,000 people in 2021.
Recent scientific studies have shown links between Alzheimer’s and the disruption of the work of neurons in the brain, along with genetic, lifestyle and environmental factors, but a specific cause for the disease remains complex and elusive.
New research to be presented at the Radiological Society of North America’s annual meeting in Chicago from Nov. 26 to Nov. 30 adds another link to identifying risk factors associated with the disease: the visceral fat surrounding internal organs in the abdomen.
Unlike subcutaneous fat — the layer of soft-feeling stuff that lies in a layer beneath your skin in your stomach — visceral fat is found in spaces around your liver and a tissue under your belly muscle that covers your intestines called the omentum.
Obesity in people aged 40 to 60 years old is a risk factor for Alzheimer's disease and increases the risk of clinical dementia, but the underlying link between the disease and obesity aren't known.
To try and identify Alzheimer's risks in people earlier, researchers analyzed data from 36 healthy people, ranging from 40 to 60 years old with a body mass index of 32 — which, as defined by the CDC, marks someone as obese. The researchers then measured their subcutaneous and visceral fat using an MRI. The thickness of the cortical regions of their brains, areas that are affected by Alzheimer’s disease, was also measured by an MRI.
The researchers found that a higher ratio of visceral to subcutaneous fat was associated with higher presence of amyloid plaques, proteins that are thought to interfere with communication between brain cells, and prime suspects in the search for what causes Alzheimer’s. The relationship between visceral fat and the amyloid plaques was found to be worse in men participants than in women.
“This study highlights a key mechanism by which hidden fat can increase the risk of Alzheimer’s disease,” said Cyrus A. Raji, associate professor of radiology and neurology, and director of neuromagnetic resonance imaging at the Mallinckrodt Institute of Radiology at Washington University School of Medicine, and the senior author of the study, in a statement. “It shows that such brain changes occur as early as age 50, on average — up to 15 years before the earliest memory loss symptoms of Alzheimer’s occur.”
The researchers also found that amounts of visceral fat are also related to an increased burden of inflammation in the brain. Inflammation of the brain is one of the main mechanisms contributing to Alzheimer’s disease, said Mahsa Dolatshahi, a post-doctoral research fellow with Mallinckrodt Institute of Radiology, and study co-author in a statement.
The findings of the study could point to visceral fat itself as being a potential target for scientific studies to see if modifying it — with anti-obesity drugs and other interventions "with a brain health perspective" — might reduce the risk of brain inflammation or dementia, Raji and Dolatshahi added.
Their study, the researchers said, indicates that by looking at risk factors like obesity and increased body fat compartmentalization, doctors might be able to identify and delay the onset of Alzheimer’s before its earliest symptoms are shown. Further studies, involving more people, and a larger time line of observation, are needed to confirm those implications, they added.
In the study, the researchers add that their findings point to the importance of exercising, strong social engagements and the Mediterranean diet, a diet that includes olive oil, fruits, vegetables, and moderate amounts of fish, dairy and meat, early in people's middle age, to "improve cognitive reserve" to prevent or delay dementia.
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