Study author Dr. Elina Ronnemaa, of Uppsala University in Sweden, said the study involved 2,269 men in Sweden who underwent glucose testing at age 50 to test for diabetes, which is caused by abnormal insulin levels.

The study, published in the American Academy of Neurology, found that during an average follow-up of 32 years, 102 participants were diagnosed with Alzheimer's disease, 57 with vascular dementia and 235 with other types of dementia or cognitive impairment.

The study also found that the men with low insulin secretion capacity at age 50 were nearly 1 1/2 times more likely to develop Alzheimer's disease than people without insulin problems. The risk remained significant regardless of blood pressure, cholesterol, body mass index and education, Ronnemaa said.

"It's possible that insulin problems damage blood vessels in the brain, which leads to memory problems and Alzheimer's disease, but more research is needed to identify the exact mechanisms," Ronnemaa said in a statement.