Patients who take some of the drugs commonly prescribed for type-2 diabetes are less likely to have Alzheimer's disease, according to several studies presented at the International Conference on Alzheimer's Disease and Related Disorders in Madrid, Spain.

The causes of Alzheimer's disease are still not well understood, but researchers told participants at the conference that diabetes and pre-diabetic conditions appear to increase the risk of Alzheimer's disease.

Two teams of researchers looked at patients who take diabetes medications known as glitazones or thiazolidinediones (TZDs), including Actos (pioglitazone) and Avandia (rosiglitazone).

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 almost 20 percent fewer new cases of Alzheimer's than those who took insulin.

Dr. David Geldmacher of the University of Virginia 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