Potbellies in midlife may flood brain with toxic substances, researcher says

From HealthDay

A potbelly in middle age more than triples the risk of senility decades later, according to a large study that pinpoints a new link between obesity and dementia.

“The take-home message is that it’s not only what you weigh, but it’s where you carry your weight in midlife,” said study author Rachel Whitmer, a research scientist with the Kaiser Permanente Division of Research, in Oakland, Calif.

The good news? Lose weight, and you may be able to reduce the increased risk, she said.

Researchers have been tracking the mental fallout of obesity for years. In 2005, Whitmer and her colleagues reported that people who were fatter in middle age were as much as 74 percent more likely to develop dementia as senior citizens.

An estimated 10 million American baby boomers will develop Alzheimer’s disease in their lifetime, according to research released earlier this month, while another study found that more than 20 percent of seniors have memory loss not classified as dementia.

In the new study, researchers looked specifically at belly fat, checking to see if it posed a risk in people even if they were otherwise not overweight.

The study examined 6,583 Kaiser Permanente health-care plan members between the ages of 40 and 45 who had their abdominal fat measured in the late 1960s and early 1970s. The researchers followed up to see what happened to them between 1994 and 2006, when they reached their 70s and beyond.

The findings were published in the March 26 online issue of Neurology.

Overall, 16 percent of those studied developed dementia, also known as senility. Researchers found that obese people who had the most abdominal fat in their 40s were 3.6 times more likely to develop dementia than those with the least amount of abdominal fat.

People who were overweight — a step below obese — and had large bellies in their 40s were 2.3 times more likely to develop dementia.

Overall, 21 percent of those with high levels of belly fat developed dementia, compared to 15 percent of others, Whitmer said.

The effects of belly fat remained even when researchers adjusted their statistics to take into account the effect of conditions such as stroke and diabetes.

It’s still possible that a factor other than abdominal fat may cause the higher rate of dementia. The study doesn’t confirm a direct cause-and-effect relationship. Still, the findings suggest that something about abdominal body fat affects the brain independently of cardiovascular disease or diabetes, Whitmer noted.

It’s not clear, however, exactly how obesity translates into reduced brain function. It may have something to do with how belly fat surrounds the body’s organs and secretes hormones and toxic substances that could disrupt the way the brain functions, Whitmer speculated.

William Thies, vice president of medical and scientific relations with the Alzheimer’s Association, said another theory is that the physical presence of belly fat and its compression of abdominal organs could burden the entire body, affecting the brain by increasing blood pressure and cholesterol. However, “whether there’s a direct biological link between body fat and Alzheimer’s has yet to be established,” he said.

Whatever the cause for the connection, all hope is not lost.

“Even with moderate exercise, you can reduce that visceral fat, the fat around the organs,” Whitmer said, adding that there’s a lot of evidence that the roots of dementia develop years before it becomes obvious, so a change now could spell a big benefit later.

From UPI.com

Low levels of high-density lipoproteins, or HDL the “good” cholesterol, in middle age may increase memory loss and dementia risk, French researchers said.

 

Lead author Archana Singh-Manoux of the French National Institute for Health and Medical Research in Paris and the University College London in England observed 3,673 Whitehall II participants. Whitehall II, which began in 1985, is long-term health examination of more than 10,000 British civil servants.

“Memory problems are key in the diagnosis of dementia,” Singh-Manoux said in a statement. “We found that a low level of HDL may be a risk factor for memory loss in late mid-life. This suggests that low HDL cholesterol might also be a risk factor for dementia.”

Researchers defined low HDL as less than 40 mg/dL and high HDL as 60 mg/dL or higher. The team compared blood-fat and memory data collected when study members were age 55 and 61.

The study found at age 55, participants with low HDL cholesterol showed a 27 percent increased risk of memory loss and at age 60, participants with low HDL had a 53 percent increased risk of memory loss.

The findings are reported in Arteriosclerosis, Thrombosis and Vascular Biology

From WSJ.com

People who have more belly fat during middle age, even those considered to be of normal weight, have higher rates of dementia when they reach old age, according to a study in the journal Neurology. The link highlights a body of work showing that health is affected by not just overall body weight but how the weight is distributed.

Too much abdominal fat, which extends into the body cavity around major organs, is known to be a risk factor for cardiovascular disease and diabetes. These new findings, published Wednesday, show that large amounts of belly fat are associated with declining cognitive function as well.

“There is something very potent about collecting fat in your belly,” said Rachel Whitmer, lead study author and a scientist at the research division of Kaiser Permanente in Oakland, Calif.

It is possible the link between belly fat and dementia is better explained by some other factor, such as poor diet, that wasn’t measured in this study, said P. Murali Doraiswamy, an Alzheimer’s researcher and chief of biological psychiatry at Duke University who wasn’t involved with the study.

Using medical records, researchers examined the belly size of 6,583 middle-age people between 1964 and 1973 and then looked to see whether those same individuals were diagnosed with dementia an average of 36 years later.

They found that just being overweight or obese nearly doubles one’s risk of dementia in old age, even after taking into account other risk factors such as diabetes and heart disease.

But having high levels of central-body fat increases the risk more, boosting an obese person’s risk 3.6 times higher than a normal-weight individual with low belly fat. And, as a group, normal-weight individuals with high levels of belly fat showed an elevated risk of dementia.

“It’s really a red flag for all of us boomers,” said Duke’s Dr. Doraiswamy. “Waist size may not be reflective of just your heart health, but your brain function decades later.”

However, Dr. Doraiswamy said there was more variability in the normal-weight group compared with heavier subjects, suggesting that some normal-weight people may be more vulnerable to dementia than others, perhaps due to a genetic predisposition. This study didn’t look at genetic risk, he said.

Why belly fat appears to wreak such havoc on the body isn’t completely understood. Fat is known to produce a variety of potentially harmful substances that cause inflammation, disrupting blood flow to the heart and possibly the brain, which could be one reason for its link to dementia, said Jean-Pierre Despres, director of research at the Quebec Heart Institute at Laval University in Quebec City, who wasn’t involved in the study. More research is needed to figure out the exact mechanisms of action, he and other experts said.

The study wasn’t able to examine whether people who lost weight during the 30-year time period decreased their risk of developing dementia, but it is an area of research interest, said study author Dr. Whitmer.

Much of where an individual accumulates fat is genetically determined, but abdominal fat is easier to lose than fat stored elsewhere. “This is not a stubborn fat,” Dr. Whitmer said. “It is a toxic fat.”