November 22, 2011 in Features

Controlling blood sugar may lower dementia risk

Shari Roan Los Angeles Times
 

Two of the most worrisome trends in health care – the soaring rates of Type 2 diabetes and dementia – have biological factors in common. And scientists are beginning to think that is more than just a coincidence.

In fact, many now believe that proper control of blood sugar could pay dividends in the future by reducing the number of people stricken by Alzheimer’s disease, other forms of dementia and even the normal cognitive decline that comes with age.

The key characteristics found in the development of heart disease and stroke – clogged arteries and inflammation in cells – also affect the brain, says Debra Cherry, executive vice president of the Alzheimer’s Association California Southland. “What is good for the reduction of diabetes risk is also good for reduction of the risk of cognitive impairment,” she says.

About 6.8 million people in the U.S. have some type of dementia. Alzheimer’s disease is the most common, affecting 5.4 million people, a number projected to double by 2040, according to the Alzheimer’s Association. The cause is unknown, although studies show people with the disease accumulate clumps of a protein called beta amyloid in their brains. There are no treatments to slow or stop the disease process.

More than 8 percent of American adults and children have either Type 1 or Type 2 diabetes, a number that is expected to grow in step with the rise in rates of obesity. Diabetes is diagnosed when the body can’t produce enough insulin or use insulin properly to remove sugar from the bloodstream. When blood sugar remains too high, it can damage organs and lead to heart disease, kidney failure, nerve damage and other complications.

Type 1 diabetes is usually diagnosed in childhood and requires insulin, while Type 2 typically involves weight gain in adulthood. Both diseases could affect cognitive health later in life.

The relationship between diabetes and dementia diseases drew headlines in September when a large study in Japan reported that people with diabetes are twice as likely to develop Alzheimer’s disease. Published in the journal Neurology, it found that even people with a level of poor glucose control that precedes diabetes were 35 percent more likely to develop some type of dementia.

An estimated 1 in 10 cases of dementia may be attributable to diabetes, says neurologist Geert Jan Biessels of Utrecht University in the Netherlands, a leading researcher on the relationship between the diseases. The process may begin decades before symptoms such as memory loss occur. He says treating diabetes and risk factors linked to it, such as hypertension and high cholesterol, may help prevent many dementia cases.

The disheartening failure in recent years to find effective treatments for Alzheimer’s disease has caused researchers to look with extra interest at the link to diabetes and other diseases such as heart disease and stroke.

“We want to find ways of intervening before people develop cognitive impairment and dementia,” says Dr. Denise G. Feil, a geriatric psychiatrist at the VA Greater Los Angeles Healthcare System.

The association between the two disorders is complicated. Researchers are exploring two general avenues: one to do with vascular disease and the other with blood sugar control.

The fact that vascular disease can lead to dementia has been known for some time. Damage to blood vessels in the brain in the form of ministrokes that decrease blood flow and kill cells can cause so-called vascular dementia – and diabetes is one of the illnesses that can accelerate this type of brain injury.

Alzheimer’s is different, but diabetes appears to play a role in that process too. Some researchers believe poor blood sugar control can make it harder for the body to clear the buildup of amyloid. Others suspect high levels of glucose create a kind of toxicity in the body related to oxidative stress, in which harmful free radical molecules damage tissue.

Free radicals are primed to react chemically with any other molecules they hit. “They bang into other molecules, causing inflammation,” Cherry says. “Amyloid plaque may be a result of inflammation, at least in part.”

Genetics also suggests that the two diseases are linked. People with a mutation known as ApoE4 have a higher risk for both Alzheimer’s disease and diabetes.

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