Diabetes may significantly increase the risk of developing Alzheimer's, a study of 824 nuns, priests, and Catholic brothers, found bolstering evidence linking the two diseases.

Participants studied were 55 and older when the research began and were followed on average about six years.

Alzheimer's developed in 151 participants, including 31 who had diabetes.

The researchers calculated that diabetics faced a 65 per cent higher risk of developing the mind-robbing disease.

The link remained strong, even when researchers factored in the prevalence of strokes - a common complication of diabetes - which are also believed to raise the risk of Alzheimer's.

Previous research has linked diabetes with memory problems and diabetes is known to damage blood vessels that supply the brain.

"This is one of the first long-term studies to follow people who start out with no evidence of Alzheimer's disease and track how having diabetes affects their risk of developing it," said William Thies, an Alzheimer's Association vice-president. "It's a powerful argument for doing everything you can to control your blood sugar."

Type 2 diabetes, most common in older people, often can be controlled and even cured through exercise and diet.

Dr. George King, of Boston's Joslin Diabetes Center, called the research "quite important in light of the fact that diabetes is exploding," with some 18 million Americans affected, a number expected to double by 2050.

If the link is real, King said there could be a corresponding surge in Alzheimer's cases.

The study - led by Drs. Zoe Arvanitakis and David Bennett and colleagues at Rush University Medical Center in Chicago - appeared tuesday in the Archives of Neurology journal.

One recent mouse study involving Joslin researchers suggests insulin abnormalities in diabetes might affect a protein called tau, which in Alzheimer's forms tangles in brain cells.