Severe hypoglycaemia and late-life cognitive ability in older people with Type2 diabetes: The Edinburgh Type2 Diabetes Study

Abstract

Objective To determine the association between lifetime severe hypoglycaemia and late-life cognitive ability in older people with Type2 diabetes. Methods Cross-sectional, population-based study of 1066 men and women aged 60-75years, with Type2 diabetes. Frequency of severe hypoglycaemia over a person's lifetime and in the year prior to cognitive testing was assessed using a previously validated self-completion questionnaire. Results of age-sensitive neuropsychological tests were combined to derive a late-life general cognitive ability factor, 'g'. Vocabulary test scores, which are stable during ageing, were used to estimate early life (prior) cognitive ability. Results After age- and sex- adjustment, 'g' was lower in subjects reporting at least one prior severe hypoglycaemia episode (n=113), compared with those who did not report severe hypoglycaemia (mean 'g'-0.34 vs. 0.05, P<0.001). Mean vocabulary test scores did not differ significantly between the two groups (30.2 vs. 31.0, P=0.13). After adjustment for vocabulary, difference in 'g' between the groups persisted (means -0.25 vs. 0.04, P<0.001), with the group with severe hypoglycaemia demonstrating poorer performance on tests of Verbal Fluency (34.5 vs. 37.3, P=0.02), Digit Symbol Testing (45.9 vs. 49.9, P=0.002), Letter-Number Sequencing (9.1 vs. 9.8, P=0.005) and Trail Making (P<0.001). These associations persisted after adjustment for duration of diabetes, vascular disease and other potential confounders. Conclusions Self-reported history of severe hypoglycaemia was associated with poorer late-life cognitive ability in people with Type2 diabetes. Persistence of this association after adjustment for estimated prior cognitive ability suggests that the association may be attributable, at least in part, to an effect of hypoglycaemia on age-related cognitive decline. © 2011 The Authors. Diabetic Medicine © 2011 Diabetes UK.