Cognitive performance in very old diabetic persons: the impact of semantic structure, preclinical dementia, and impending death.

The authors examined the associations of diabetes mellitus with cognitive performance in a population-based sample of nondemented and nondepressed very old persons. Diabetic participants (n = 31) were compared with nondiabetic controls (n = 307), adjusting for age, educational level, and related vascular diseases and signs. Results showed that diabetic persons performed significantly worse on tests of verbal fluency and episodic memory but that the effects on both types of abilities were less pronounced in tasks involving higher degrees of semantic structure. Follow-up analyses further revealed that preclinical dementia and impending death accounted for much of the observed associations. The results suggest that cognitive deficits among very old diabetics are most likely detected by tasks that draw less on semantic structures and that the most robust effects may be found in letter fluency performance.