Severe hypoglycaemia and late-life cognitive ability in older people with Type 2 diabetes: the Edinburgh Type 2 Diabetes Study.
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.
Centre for Population Health Sciences, University of Edinburgh, Edinburgh, UK.
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Aung
M W J
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Strachan
B M
BM
Frier
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Butcher
I J
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Deary
J F
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Price
D000367:Age Factors; D000368:Aged; D001007:Anxiety / Q000209:etiology / Q000523:psychology*; D003071:Cognition; D003072:Cognition Disorders / Q000453:epidemiology / Q000209:etiology / Q000523:psychology*; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003863:Depression / Q000453:epidemiology / Q000209:etiology / Q000523:psychology*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications / Q000453:epidemiology / Q000523:psychology*; D004522:Educational Status; D005260:Female; D006442:Glycated Hemoglobin / Q000378:metabolism; D006801:Humans; D007003:Hypoglycemia / Q000150:complications / Q000453:epidemiology / Q000523:psychology*; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012307:Risk Factors; D012606:Scotland; D012720:Severity of Illness Index; D012737:Sex Factors; D011795:Surveys and Questionnaires
D006442:Glycated Hemoglobin; D007004:Hypoglycemic Agents; C517652:hemoglobin A1c protein, human