Severe hypoglycaemia and late-life cognitive ability in older people with Type 2 diabetes: the Edinburgh Type 2 Diabetes Study

Diabet Med. 2012 Mar;29(3):328-36. doi: 10.1111/j.1464-5491.2011.03505.x.

Abstract

Objective: To determine the association between lifetime severe hypoglycaemia and late-life cognitive ability in older people with Type 2 diabetes.

Methods: Cross-sectional, population-based study of 1066 men and women aged 60-75 years, with Type 2 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 Type 2 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Age Factors
  • Aged
  • Anxiety / etiology
  • Anxiety / psychology*
  • Cognition Disorders / epidemiology
  • Cognition Disorders / etiology
  • Cognition Disorders / psychology*
  • Cognition*
  • Cohort Studies
  • Cross-Sectional Studies
  • Depression / epidemiology
  • Depression / etiology
  • Depression / psychology*
  • Diabetes Mellitus, Type 2 / complications
  • Diabetes Mellitus, Type 2 / epidemiology
  • Diabetes Mellitus, Type 2 / psychology*
  • Educational Status
  • Female
  • Glycated Hemoglobin A / metabolism
  • Humans
  • Hypoglycemia / complications
  • Hypoglycemia / epidemiology
  • Hypoglycemia / psychology*
  • Hypoglycemic Agents / therapeutic use*
  • Male
  • Middle Aged
  • Neuropsychological Tests
  • Risk Factors
  • Scotland
  • Severity of Illness Index
  • Sex Factors
  • Surveys and Questionnaires

Substances

  • Glycated Hemoglobin A
  • Hypoglycemic Agents
  • hemoglobin A1c protein, human