TUESDAY, Aug. 12 (HealthDay News) -- Earlier onset, longer duration and greater severity of diabetes may increase the risk for mild cognitive impairment, according to Mayo Clinic researchers.

Previous research identified a link between mild cognitive impairment and diabetes. Poor blood glucose (sugar) control over a long period of time may lead to a loss of brain cells, according to background information in a news release about the study.

In addition, diabetes is associated with cardiovascular disease risk and stroke, which may increase the risk of cognitive impairment.

This new study of people ages 70 to 89 found that rates of diabetes were similar among 329 participants with mild cognitive impairment (20.1 percent) and 1,640 participants without mild cognitive impairment (17.7 percent).

However, the researchers found an association between mild cognitive impairment and developing diabetes before age 65, having diabetes for 10 years or longer, being treated with insulin, and having diabetes-related complications.

The findings were published in the August issue of the journal Archives of Neurology.

"Severe diabetes mellitus is more likely to be associated with chronic hyperglycemia [high blood glucose], which, in turn, increases the likelihood of cerebral microvascular disease and may contribute to neuronal damage, brain atrophy and cognitive impairment," the study authors wrote.

They said the fact that people with the eye disease diabetic retinopathy were twice as likely to have mild cognitive impairment supports the theory that diabetes-related damage to blood vessels in the brain may contribute to the development of cognitive problems.

"Our findings suggest that diabetes mellitus duration and severity, as measured by type of treatment and the presence of diabetes mellitus complications, may be important in the pathogenesis of cognitive impairment in subjects with diabetes mellitus," the Mayo researchers concluded. "In contrast, late onset of diabetes mellitus, short duration of diabetes mellitus or well-controlled diabetes mellitus may have a lesser effect."

More information

The Alzheimer's Association has more about mild cognitive impairment.