Objective: To determine whether cognitive impairment is associated with changes in self-care behaviour and use of health and social services in older subjects with diabetes mellitus.
Research design and methods: This was a community based, case-control study of subjects registered with general practices participating in the All Wales Research into Elderly (AWARE) Diabetes Study. The 396 patients aged 65 years or older with known diabetes mellitus were compared with 393 age- and sex-matched, non-diabetic controls. Adjusted odds ratio estimates of normal performance on Mini-Mental State Examination (MMSE) and Clock Drawing Test (numbers and hands) were determined. Information on self-care behaviours and use of services was obtained.
Results: A total of 283 (71%) diabetic subjects scored 24 or more on MMSE, compared with 323 (88%) of controls (OR 0.54, P<0.0005). The mean (S.D.) scores were 24.5 (5.1) and 25.7 (4.3), respectively (difference between means 1.22; 95% CI 0.56, 1.88; P<0. 001). Clock testing demonstrated that 257 (65%) and 286 (72%) diabetic subjects correctly placed the numbers and hands, respectively, compared with 299 (76%) and 329 (84%) of controls (OR 0.59, P<0.001 and P<0.52, P<0.0005, respectively). Both test scores declined with increasing age, earlier school leaving age and deteriorating visual acuity. Of other variables examined, only need for oral hypoglycaemic drugs or insulin, history of stroke, dementia or Parkinson's disease and symptoms of autonomic neuropathy significantly impaired one or more cognitive test scores. The odds ratios (95% CI) for normal cognitive test results in subjects with diabetes after adjusting for all significant variables was 0.74 (0. 56, 0.97), P=0.029 for MMSE scores and 0.63 (0.44, 0.93), P=0.019, and 0.58 (0.38, 0.89), P=0.013, for the numbers and hands parts of the clock test, respectively. In comparison with diabetic subjects with no evidence of cognitive impairment, diabetic subjects with an MMSE score <23 were significantly less likely to be involved in diabetes self-care (P<0.001) and diabetes monitoring (P<0.001). A low MMSE score was also significantly associated with higher hospitalisation in the previous year (P=0.001), reduced ADL (activities of daily living) ability (P<0.001) and increased need for assistance in personal care (P=0.001).
Conclusions: Elderly subjects with predominantly Type 2 diabetes mellitus display significant excess of cognitive dysfunction, associated with poorer ability in diabetes self-care and greater dependency. Routine screening of cognition in older subjects with diabetes is recommended.