In 1999, the Rotterdam Study uncovered the strong association between diabetes and Alzheimer's disease. In this landmark study carried out in the Netherlands, 6,370 elderly men and women were followed for an average of two years. In what was perhaps one of the first reports on this issue, they found that having diabetes almost doubled the risk of dementia. Since then, several studies have confirmed these findings, and threw light on the probable mechanism for this connection.
A nine-year study published in 2004 followed 842 older Catholic nuns, priests and brothers. Although none of them had any signs of Alzheimer's at the beginning of the study, at the end of it, 151 of them had developed Alzheimer's. A statistical analysis found that those who had type 2 diabetes had a 65 percent increased risk of getting Alzheimer's. Later, it was also found that this increased risk applies to both type 1 and type 2 diabetes.
Type 1 diabetes frequently occurs before the age of 20. It is caused by antibodies destroying the pancreas, the organ that produces insulin. This type of diabetes occurs in 10 to 15 percent of diabetics. In type 2 diabetes, which occurs in 85 to 90 percent of diabetics, the cause is primarily a condition called "insulin resistance" where insulin just doesn't work as it is supposed to do. Type 2 diabetes has a strong genetic component but, initially at least, can be prevented with changes in diet and lifestyle.