May 27, 2004
Many seniors have diabetes, putting them at potential risk for Alzheimer's, a new study shows. Diabetes has long been known to raise the risk for heart disease, strokes, kidney failure, vision loss, and other serious conditions. Mental decline and Alzheimer's may now be added to the list of ills associated with diabetes, according to this latest report.
About one in five people over age 65 has type 2 diabetes, a chronic age-related ailment marked by poor control of blood sugar (glucose). Diabetes is especially common in older people who are overweight, though it is becoming increasingly common in younger persons as well, including children and teens, who carry excess pounds. Many people with diabetes must take daily injections of insulin, a hormone released by the pancreas, to help control their blood sugar.
In this latest study, part of the large and ongoing Religious Orders' Study, researchers at Rush University Medical Center in Chicago followed 824 elderly Catholic nuns, priests, and brothers for an average of 5.5 years. They were given regular physical examinations and mental tests to look for signs of memory loss and other problems with their thinking skills. About 15 percent (127) of them had diabetes.
During the study, 151 of the men and women developed Alzheimer's disease. Those with diabetes were 65 percent more likely to be diagnosed with Alzheimer's than those who did not have diabetes.
Consistent with Earlier Findings
The results are consistent with two large earlier studies that found that diabetes nearly doubled the risk of developing Alzheimer's disease.
The researchers speculate that diabetes may increase Alzheimer's risk through various possible pathways. For example, diabetes damages blood vessels in many parts of the body. It may affect blood vessels in the brain as well, impairing blood flow and damaging critical brain functions, including those involving memory.
Poor control of blood sugar levels by the hormone insulin, a hallmark of diabetes, also affects the brain. For example, scientists at the Fisher Center for Alzheimer's Research at The Rockefeller University showed a few years ago that unregulated insulin may raise levels of beta amyloid, a toxic protein that builds up in the brains of those with Alzheimer's.
One of the important things to remember is that, in general, factors that put you at higher risk for heart disease and stroke, like diabetes, also increase your risk for Alzheimer's disease. Your chances of developing type 2 diabetes can be lessened by lifestyle changes (e.g., exercise and diet). Although it's not yet known whether such lifestyle changes can affect Alzheimer's risk, many researchers are betting that developing heart-healthy habits can decrease the risk of Alzheimer's disease.
It's also important to note that having diabetes does not mean that you will develop Alzheimer's as you age. Rather, diabetes may put you at increased risk for developing the disease. Similarly, many people who develop Alzheimer's do not have diabetes. Of the 151 elderly men and women who were diagnosed with Alzheimer's during the current study, 31 had diabetes.
There appear to be many risk factors for Alzheimer's disease, including genes, years of formal education, heart disease, strokes, being overweight, and more. Diabetes appears to be one more risk factor for this devastating illness.
For more on Alzheimer's risk factors, visit www.ALZinfo.org.
The study was published in the May 2004 issue of the Archives of Neurology, a research journal for physicians.
Zoe Arvanitakis, MD, Robert S. Wilson, PhD, Julia L. Bienias, ScD, et al: "Diabetes Mellitus and Risk of Alzheimer Disease and Decline in Cognitive Function." Archives of Neurology 2004:Volume 61, pages 661-666.