Brain Atrophy, Lesions Found in Type 1 Diabetics; May Indicate Cognitive Impairment in Diabetics Begins Early

BUFFALO, N.Y. -- Cerebral atrophy is common in young persons with juvenile-onset diabetes, and there is evidence that small blood vessels within the brain's white matter are damaged in these patients, neurologists at the University at Buffalo and the University of Western Ontario have found.

Both findings, which are preliminary, may be important in understanding the development of cognitive impairment seen in older diabetics, said Richard K.T. Chan, M.D., assistant professor of neurology and neurosurgery in the UB School of Medicine and Biomedical Sciences and first author on the study. Vladimir Hachinski, M.D., of the University of Western Ontario, is co-investigator.

"Although brain involvement in diabetes has been suspected, this is the first study that approaches the problem in a systematic manner," Chan said. "Persons with type 1 diabetes comprise a unique population, because insulin was introduced only about 50 years ago. These people now are entering the golden years, and their quality of life can be significantly impacted by impaired brain function."

Results of the research were presented at the annual meeting of the American Academy of Neurology held recently in Honolulu.

The investigations are part of the Study of Cognitive Impairment and MRI Abnormality among Diabetics (SCIMAD) being conducted by the two institutions. The goal is to determine the prevalence of cognitive impairment among young, otherwise healthy patients with juvenile-onset diabetes and to correlate impairment with neuroimaging results and clinical indicators.

This disease also is called type 1, or insulin-dependent diabetes, because the primary symptom is the inability of the pancreas to produce insulin, requiring patients to receive insulin injections throughout their lifetime. Type 2, or adult-onset diabetes, may be controlled by diet and exercise, although many patients with type 2 diabetes require medications (including insulin) to control their blood sugar concentration.

While prior studies have suggested a relationship between diabetes and cognitive functioning, the pathway through which the damage occurs is not known, Chan said. Impairment may range from poor school performance in childhood to decreased work output and forgetfulness in adulthood.

Formal testing of brain function often reveals problems in abstract reasoning skills, eye-hand coordination and other subtle impairments in brain function, Chan noted. More recent studies also suggested that diabetes is a risk factor for dementia, including Alzheimer's disease in the elderly.

One of the problems with such findings is that much research on diabetes and cognitive impairment, particularly that concerning cerebral small vessel disease (CSVD), has been done in older persons with type 2 diabetes, where outcomes may be affected by hypertension or other chronic conditions of aging, Chan noted. The SCIMAD study was designed to study the relationship in young, otherwise healthy juvenile-onset diabetics, in hopes of learning when and where the cognitive damage begins.

There were 26 diabetic and 24 non-diabetic persons in the cerebral-atrophy study, and 33 diabetic and 20 non-diabetic participants in the white-matter-lesion study. All participants were between the ages of 18 and 50. Diabetics were diagnosed before the age of 18 and had the disease for 10 years or more. The same study population was used for both investigations.

About half of the participants were enrolled through UB, the lead institution, and half through the University of Western Ontario. All participants received brain scans using magnetic resonance imaging that were analyzed for cerebral volume and the presence of ischemic white-matter lesions at the UB-affiliated Buffalo Neuroimaging Analysis Center.

Results showed that 23 of the diabetics, or 88.5 percent, had brain volumes lower than the median for control subjects.

MRIs of six diabetics, or 15 percent, showed ischemic white-matter lesions; none were found in the controls.

Researchers will conduct cognitive function tests and compare those results with the neuroimaging results when a full cohort of 100 diabetics and 100 controls has enrolled.

"The studies provide clues to the potential neurological problems associated with diabetes, including dementia and strokes," Chan said. "The next step is for us to identify the mechanism that leads to changes in structure, and perhaps we can design treatments to slow down or prevent disease progression."

The study was supported by a grant from the Juvenile Diabetes Research Foundation International.