Dr. Jane S. Saczynski, of the University of Massachusetts Medical School, Worcester, and colleagues examined the association of glycemic status and magnetic resonance imaging (MRI) findings of brain pathological changes in 4,415 elderly residents of Iceland (mean age, 76 years) without dementia participating in the Age Gene/Environment Susceptibility-Reykjavik Study.
Overall, 2,327 (53%) were normoglycemic, 1,599 (36%) had impaired fasting glucose, and 489 (11%) had Type 2 diabetes.
After adjustment for demographic and cardiovascular risk factors, Type 2 diabetic patients had significantly lower total brain volume (71.5% vs. 72.2%), gray matter volume (44.9% vs. 45.1%), and white matter volume (25.3% vs. 25.7%) compared to normoglycemic subjects.
Patients with Type 2 diabetes were also more likely to have single (odds ratio 1.45) or multiple (OR 2.27) cerebral infarcts, compared to normoglycemic individuals.
Longer duration of diabetes was associated with lower percentage of total brain volume, lower percentage of gray and white matter, and higher percentage of white matter lesions, as well as with a significantly greater likelihood of having single or multiple cerebral infarcts.
In secondary analyses, use of diabetes medication and hemoglobin A1c levels were examined in relation to brain tissue volumes and the presence of cerebral infarcts. Just more than half -- 56% -- of diabetic subjects were taking either hypoglycemic medications or insulin.
Compared with diabetics who were not taking medication, patients on medication had a significantly lower percentage of total brain volume (adjusted mean percentage 70.9 vs. 72.4) and lower percentages of gray matter (44.5 vs. 45.4) and white matter (24.9 vs. 25.6) volume, according to the report.
The authors found no association between quartiles of A1c and brain tissue volumes or the presence of infarcts.
"These findings are based on cross-sectional data and should be replicated in longitudinal studies," the research team points out.
Diabetes Care Sept, 2009;32:1608-1613.