Diabetes mellitus (DM) is associated with a decline in cognitive and affective functions. Methods: In all, 182 outpatients with DM were investigated for associations of cognitive and affective functions with diabetes-related factors and cerebral white matter abnormalities. In addition, the difference in cognitive decline of age-matched late elderly normal subjects and DM patients was investigated. Results: The present study revealed that cognitive and affective functions declined in some DM patients. Furthermore, the decline in these functions was unrelated to fasting blood sugar level but was related to glycosylated hemoglobin (HbA1c) and insulin resistance. Poor HbA1c control was associated with a significant decline in the 'calculation' subscale and insulin resistance for 'naming', 'read list of letters' and 'delayed recall' Montreal Cognitive Assessment (MoCA) subscale scores. Magnetic resonance imaging scans showed that both periventricular hyperintensity (PVH) and deep white matter hyperintensity were associated with Mini Mental State Examination (MMSE) and MoCA scores, but only PVH was related to homeostasis model assessment of insulin resistance scores. Compared with age-matched late elderly normal subjects, 'orientation to time' and 'registration' MMSE subscales declined in late elderly DM patients. Conclusions: These results suggest that cognitive and affective decline in DM patients was mostly related to glucose control and insulin resistance, whilst amongst late elderly subjects the impairment of 'attention' and 'orientation' were characteristic features of DM patients.
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