Study Links Diabetes to Risk of Alzheimer’s

A study of 824 people for more than five years finds that those with diabetes had a 65 percent greater risk of developing Alzheimer's. By LISA GREENE, Times Staff Writer

People with diabetes may have a greater risk of developing Alzheimer's disease, a new study says, meaning that rates of Alzheimer's could increase even faster than expected. More than 4-million Americans already have Alzheimer's, a number expected to roughly triple by 2050 as the population ages. But diabetes also is increasing at epidemic rates. So if it contributes to Alzheimer's, the number of Americans living with the debilitating brain disorder could grow even faster.

"It is kind of scary thinking about the idea of a diabetes epidemic in conjunction with the other factors of Alzheimer's," said Neil Buckholtz, chief of the Dementias of Aging Branch of the National Institute on Aging, which funded the study. In the study, published Monday in the Archives of Neurology, patients with diabetes had a 65 percent greater risk of developing Alzheimer's.

The results should be a call for people with diabetes to work even harder to control their blood sugar, and for people at risk for diabetes to change their diet and exercise habits to lower that risk, Alzheimer's experts said. "Our whole position is trying to get people to take care of their health sooner rather than later," said Gloria Smith, president of the Florida Gulf Coast chapter of the Alzheimer's Association. "This is one of those things that shows healthy aging should get started as soon as possible." Other studies have linked high blood pressure and high cholesterol to Alzheimer's.

The study, conducted by the Rush Alzheimer's Disease Center in Chicago, followed 824 Catholic nuns, priests and brothers for more than five years. All the patients, enrolled in the ongoing Religious Orders Study, were over age 55, and 127 had diabetes. During the study period, 151 patients were diagnosed with Alzheimer's, including 31 who also had diabetes. Scientists found the 65 percent greater Alzheimer's risk after accounting for differences in age, gender and education levels.

"These are two extremely common problems that are getting to be even bigger problems, and we need to better understand what causes these conditions," said Dr. Zoe Arvanitakis, assistant professor of neurological sciences at Rush University Medical Center and the study's lead author. The increased risk could be greater than 65 percent.

People with diabetes often die from other health problems before they develop Alzheimer's symptoms, said Huntington Potter, interim CEO of the fledgling Johnnie B. Byrd Sr. Alzheimer's Center & Research Institute in Tampa. "It's very worrisome," Potter said. "We all are faced with changes in our lifestyle." The number of people with diabetes in the United States more than doubled, from 5.8-million to 13.3-million between 1980 and 2002, federal studies say.

Most of the increase is in type 2 diabetes, which is linked to obesity and lack of exercise. In type 2 diabetes, the body either doesn't make enough insulin or can't use insulin properly to control blood sugar. (About 5 to 10 percent of diabetics have type 1 diabetes, which usually develops among children and young adults and is not linked to weight.) Diabetes already is linked to other health problems, including heart disease, kidney failure, blindness and amputations. Even so, Smith said, the Alzheimer's link will hit home for diabetes patients. "We're all afraid of different diseases, but when it comes to Alzheimer's, that's terrifying for people," she said.

A few earlier studies looked at diabetes and Alzheimer's but had contradictory results. The new study likely will prompt more research, Buckholtz said. One such study is looking at whether a drug used to treat diabetes might help Alzheimer's patients. Scientists aren't sure how diabetes might contribute to Alzheimer's. But they pointed to a few possibilities. Diabetes could damage blood vessels in the brain. Or high levels of sugar could damage proteins in and around neurons, Potter said. Research on how that happens could have applications beyond diabetes. "It may give us tremendous insight into other mechanisms by which the disease can be exacerbated," Potter said.

Rush scientists hope to answer that question more definitively after examining the brains of the study participants after they die. When they enrolled in the study, the participants agreed to donate their brains after death. The study also tested the participants each year for different types of thinking abilities, from verbal memory to the ability to recognize patterns. The patients with diabetes were 44 percent more likely to have declining results on one test over time. That test measured "perceptual speed," such as how fast it took to recognize whether two strings of numbers were the same. The participants with diabetes began the study period with lower overall scores on the tests. But on the other types of tests, they did not show any greater declines.

LIVING WITH DIABETES AND PREDIABETES People with diabetes can reduce their risk of developing life-threatening complications by changing their diet and exercising regularly. Many people with diabetes also take insulin or other medications. People at risk for diabetes may have been diagnosed with prediabetes, or with blood sugar that is higher than normal, but not high enough to be diabetic. Recent studies have shown that people with prediabetes can delay, or even prevent, diabetes by exercising and losing weight. Even a small weight loss, such as five to 10 percent of body weight, reduces the risk. Source: American Diabetes Association

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