Diabetes and Dementia

Diabetes and pre-diabetic conditions appear to increase the risk of Alzheimer's disease, but drugs that help regulate blood sugar may help patients with dementia as well, researchers report.

Several studies presented show that patients who take some of the drugs commonly prescribed to type-2 diabetes patients were less likely to have Alzheimer's disease. The findings concern Alzheimer's disease experts, who say the global explosion of diabetes may also increase the burden of Alzheimer's disease, already the leading cause of dementia. Many more people will be at risk of Alzheimer's disease as the large "baby boomer" generation ages, said William Thies, vice president of medical and scientific relations for the U.S.-based Alzheimer's Association. "It is only going to get worse," he said in an interview. "We are going to have profound aging... We are likely to bankrupt the health-care systems in most of the Western world."

There is no cure for Alzheimer's disease or other forms of dementia, which affect an estimated 28 million people globally. More than 4 million people have Alzheimer's disease in the United States alone. The causes of Alzheimer's disease are poorly understood, but it has been linked with diet and exercise, and researchers told participants at the International Conference on Alzheimer's Disease and Related Disorders that they found clear links with diabetes.

Two teams looked at patients who take diabetes medications known as glitazones or thiazolidinediones (TZDs), including pioglitazone, and rosiglitazone, Avandamet and Avandaryl.

Donald Miller of the Boston University School of Public Health looked at 142,328 Department of Veterans Affairs patients and found that those prescribed TZDs had lower rates of Alzheimer's. They estimated that the veterans taking TZDs had almost 20 percent fewer new cases of Alzheimer's than those who took insulin.

Dr. David Geldmacher of the University of Virginia and colleagues tested pioglitazone in Alzheimer's patients who did not have diabetes. Alzheimer's appeared to progress more slowly in the 12 out of 25 patients who took pioglitazone.

Several studies also found that people with poor blood sugar control have a higher risk of Alzheimer's.

Dr. Weili Xu and colleagues from the Karolinska Institutet in Sweden followed 1,173 people aged 75 and older for nine years. More than 300 developed Alzheimer's.

Those with borderline diabetes had an almost 70 percent increased risk of developing dementia and Alzheimer's disease, Xu's team told the conference.

Rachel Whitmer of Kaiser Permanente in Oakland, California, studied 22,852 patients with type 2 diabetes for eight years and found those with very poor blood sugar control were much more likely to develop dementia. Those with the worst long-term blood sugar levels were 78 percent more likely to develop dementia.

Nearly one third of U.S. adults have either type-2 diabetes or higher than normal blood sugar levels, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

"Physical activity is probably the single best way to regulate your blood sugar levels," Thies said.

He said the studies show that the TZD or glitazone drugs might be promising not only to treat, but to prevent Alzheimer's.

The research was presented July 16 to the world's largest Alzheimer's conference, ICAD 2006, in Madrid, Spain. It was selected by ICAD organizers to be highlighted because of a growing sense of the relationship between diabetes and Alzheimer's.