Severe hypoglycemia and cognitive decline in older people with type 2 diabetes: the Edinburgh Type 2 Diabetes Study

ObjectivePeople with type 2 diabetes are at increased risk of age-related cognitive decline and dementia. Hypoglycemia is a candidate risk factor, but the direction of association between episodes of severe hypoglycemia and cognitive decline in type 2 diabetes remains uncertain.Research Design and MethodsIn the Edinburgh Type 2 Diabetes Study (ET2DS), cognitive function was assessed in 831 adults with type 2 diabetes (60-75 years) at baseline and after 4 years. Scores on seven neuropsychological tests were combined into a standardized general ability factor 'g'. Self-reported history of severe hypoglycemia at baseline (history of hypoglycemia) and at follow-up (incident hypoglycemia) was recorded.Results9.3% subjects reported a history of hypoglycemia; 10.2% reported incident hypoglycemia. Incident hypoglycemia was associated with poorer cognitive ability at baseline (age- and sex-adjusted OR for lowest tertile of g 2.04; 95% CI 1.25, 3.31; p=0.004). Both history of hypoglycemia and incident hypoglycemia were also associated with greater cognitive decline during follow up (mean follow-up g adjusted for age, sex, baseline g, -0.25 versus 0.03, p=0.02 and -0.28 versus 0.04, p=0.01 respectively), including after addition of vascular risk factors, cardiovascular and microvascular disease to the models (-0.23 versus 0.03, p=0.04 and -0.21 versus 0.05, p=0.03, respectively).ConclusionsThe relationship between cognitive impairment and hypoglycemia appeared complex, with severe hypoglycemia associated with both poorer initial cognitive ability and accelerated cognitive decline.