"We know there’s a link,” says Heather Snyder, senior associate director of Medical and Scientific Relations for the Alzheimer’s Association. “What we’re trying to find out is the why.”
Snyder is speaking of two of this country’s worst scourges: Alzheimer’s disease and diabetes. Both are major killers. According to the Centers for Disease Control and Prevention, they are, respectively, the sixth and seventh leading causes of death in the U.S.
Now, research has begun to suggest that they share something else besides a capacity for death—namely, a common organic thread. For that reason, research into one may lead to successful means of dealing with the other.
To begin with, 26 million people in the U.S. have diabetes, 7 million of whom don’t even know they are affected, according to the National Institute of Diabetes and Digestive and Kidney Disease. But regardless of awareness, diabetes remains a condition whereby too much sugar builds up in the bloodstream because the body cannot use insulin effectively. That is, the body stops producing sufficient insulin to help cells absorb sugar and turn it into energy.
Certain segments of the population have a disproportionate rate of diabetes, including Hispanic, African, Asian and Native Americans. According to the National Institutes of Health, 8.3 percent of the U.S. population have diabetes, but more than 16.1 percent of the adult population of American Indians and Alaska Natives have been diagnosed with it. The rates of diabetes vary by region, with American Indians in southern Arizona suffering the highest rates in the country at 33.5 percent.
Diabetes and Alzheimer’s have several links. For example, insulin resistance and type 2 diabetes increase the risk of both heart disease and stroke. Damaged blood vessels can result from either of these conditions, and researchers believe that damaged vessels in the brain may well contribute to Alzheimer’s.
Further, our brain cells use a high level of energy, which can be affected by diabetes because the disease retards the body’s ability to absorb sugar to generate the necessary energy. Healthy brain function also depends on a symphony of many different chemicals working in concert. Too much insulin can throw off the balance of these chemicals and potentially trigger Alzheimer’s. Finally, high blood sugar causes inflammation, which could damage brain cells and help Alzheimer’s develop.
Tackling the connection between diabetes and Alzheimer’s disease may ultimately involve a better understanding of vascular dementia, a disease with the same symptoms as Alzheimer’s. But as Snyder puts it, “Of the top 10 causes of death in the United States, Alzheimer’s is the only one without any way to prevent, cure or slow its progression.” Vascular dementia, by contrast, can be prevented or managed through many of the same healthy habits that can also reduce the risk of diabetes.
“[Vascular dementia] results from hypertension, a high-fat diet, smoking and uncontrolled diabetes,” says Carson Henderson, associate director of Two Hawk Institute, an Indian-owned and -operated corporation focused on health education, training and research in Indian country. “If you exercise, eat right, and don’t smoke, you might be able to prevent vascular dementia as you age.”
Vascular dementia is caused by low blood flow to the brain, often as the result of a stroke or series of strokes. “With vascular dementia, your brain cells are dying, because small, tiny blood vessels in the brain are being blocked, and the cells below are not receiving blood or oxygen,” explains Carson Henderson’s husband, Neil Henderson, Oklahoma Choctaw, who directs the American Indian Diabetes Prevention Center at the University of Oklahoma Health Sciences Center’s College of Public Health. “Vascular dementia looks a lot like Alzheimer’s disease, but it is not the same causation. You still get memory loss and confused thinking.”
The latest link between diabetes and dementia was established by a recent study undertaken by Kyushu University in Japan. Researchers analyzed “1,017 community-dwelling dementia-free subjects” over the course of 15 years and found that Alzheimer’s disease and vascular dementia “were significantly higher in subjects with diabetes then in those with normal glucose tolerance.”
Snyder puts the significance of the finding this way: “Diabetes affects your heart, and there are links between cardiovascular health and brain health. The brain uses 25 percent of the oxygen in blood for its functions, if the heart isn’t healthy, the brain won’t be healthy, either.”
So the ties between diabetes and heart disease and stroke continue to be uncovered. Now, with the possibility that diabetes might be among the causes of one of America’s most lethal diseases, organizations like the Alzheimer’s Association are doing everything they can to spread awareness—and prevention.