Cognitive and affective disorders in elderly diabetics.

In non-insulin-dependent diabetes mellitus, performance of complex cognitive tasks requiring the storage and retrieval of new information is poorer than in age-matched controls. By contrast, performance of less demanding tasks such as immediate memory and simple reaction time is essentially equivalent for NIDDM patients and controls. This pattern parallels the cognitive change observed with normal aging, in which age differences are minimal on less demanding immediate memory tasks but older adults perform more poorly than young adults on secondary or long-term memory tasks. Age-related changes in cognitive performance have been attributed to a reduction in processing resources or working memory capacity. Although the explanation for NIDDM-related deficits remains to be identified, reduced glucose control and elevated levels of triglycerides appear to play some role in cognitive impairment. Non-insulin-dependent diabetes is associated not only with elevated levels of depression, but with an increased frequency of self-reported memory problems. Moreover, elevated levels of depression are associated with various indicators of neuropathy and with significant reductions in self-regulated control of glucose at the time of medical office visits. Diabetic patients may perceive less control over their lives as a result of the many restrictions associated with the disease. When provided with the opportunity to exercise control, however, performance on many cognitive tasks can be improved in NIDDM as well as in age-matched controls. This suggests that by providing NIDDM patients with opportunities to exercise increased control over their lives it may be possible to enhance motivation and to increase the likelihood of the patient's adopting more effective self-regulatory behaviors.