Cognition in the Early Stage of Type 2 Diabetes

OBJECTIVE: Type 2 diabetes is known to be associated with decrements in memory and executive functions and information-processing speed. It is less clear, however, at which stage of diabetes these cognitive decrements develop and how they progress over time. In this study, we investigated cognitive functioning of patients with recent screen-detected type 2 diabetes, thus providing insight into the nature and severity of cognitive decrements in the early stage of the disease. Possible risk factors were also addressed. RESEARCH DESIGN AND METHODS: Included in this study were 183 diabetic patients from a previously established study cohort and 69 control subjects. A full neuropsychological assessment, addressing six cognitive domains, was made for each participant. Raw test scores were standardized into z scores per domain and compared between the groups. Possible risk factors for cognitive decrements were examined with multivariate linear regression. RESULTS: Relative to scores for the control group, mean z scores were between 0.01 and 0.2 lower in the diabetic group across all domains, but after adjustment for differences in IQ between patients and control subjects, only memory performance was significantly reduced (mean difference −0.15 [95% CI −0.28 to −0.03]). A history of macrovascular disease and current smoking were significant determinants of slower information-processing speed in patients with diabetes. CONCLUSIONS: This study shows that modest cognitive decrements are already present at the early stage of type 2 diabetes. A history of macrovascular disease and smoking are significant risk factors for some early decrements.