Diabetes Linked to Cognitive Problems

Aug. 12, 2008 -- Adults who have severe or long-term diabetes or who develop the disease before age 65 have an increased risk of mild but noticeable memory problems.

Researchers reporting in the August issue of Archives of Neurology have linked mild cognitive impairment to earlier onset, longer duration, and greater severity of diabetes.

Mild cognitive impairment is a condition marked by mild forgetfulness, language difficulties, and other cognitive problems that are noticeable but do not interfere with everyday tasks. It is considered a transition stage between normal aging and dementia (including Alzheimer's disease), according to the journal article.

The new findings confirm results from previous studies, which have suggested an association between diabetes and declining cognitive function. Diabetes also raises one's risk of cardiovascular disease, including stroke, which can make cognitive problems more likely.

For the current study, Rosebud O. Roberts, MBChB, and colleagues at the Mayo Clinic in Rochester, Minn., compared 329 adults aged 70 to 89 with mild cognitive impairment to 1,640 people of the same age who did not have any type of cognitive impairment. Each participant had a neurological exam, neuropsychological evaluation, and lab work to measure fasting blood glucose (blood sugar) levels. Researchers asked the participants questions about their diabetes history, treatment, and complications. Medical records were used to confirm their diabetes history.

Similar rates of diabetes were noted between the two groups (20.1% for the impaired group vs. 17.7% for the unimpaired participants).

However, those with mild cognitive impairment were more likely to:

• Have developed diabetes before age 65
• Have had the disease for 10 or more years
• Require insulin treatment
• Have complications of the disease

Roberts' team says severe diabetes is more likely to be associated with poorly controlled blood sugars, which can damage nerve cells in the brain and lead to cognitive impairment.

Diabetes-related damage to blood vessels may also lead to cognitive problems. People with diabetic retinopathy, a complication of diabetes that affects small blood vessels in the eyes, are twice as likely to have mild cognitive impairment, a finding that supports this theory, study authors add.