To determine cognitive and memory dysfunction associated with non-insulin-dependent diabetes mellitus (NIDDM) and its relationship with depression, metabolic control, and serum lipids.
We studied a well-characterized group of 20 elderly patients with NIDDM and 22 control subjects with normal glucose tolerance recruited from a larger population-based sample. In addition to clinical and laboratory examinations, self-rating questionnaires that assess minor psychiatric disorder (General Health Questionnaire) and depression (Zung scale) were completed by patients and control subjects. Memory was examined with digit and block-span tests, word-list learning, Heaton Visual Memory Test, and Moss Visual Span Test. Executive functions were examined by Trail-Making A and A and B test and by Verbal and Category Fluency Tests. Visuoconstructive reasoning was examined with the block design subtest of the Wechsler Adult Intelligence Scale.
The NIDDM patients showed preserved memory span, but poor performance in learning tasks compared with control subjects. The patients recalled no fewer words than the control subjects, but the process of learning seemed to be different in the two groups. The recognition of the learned words was not impaired. Elevated serum total and very-low-density lipoprotein triglyceride levels, measured either before examinations or 5 or 10 years earlier, were associated with effects on retrieval from semantic memory in NIDDM patients.
The NIDDM patients had impaired control of their learning processes. Elevated serum triglyceride levels may be related to control of mental processing in diabetic patients.