Hypoglycaemia in children and adults with type 1 diabetes: clinical implications
Graveling, Alex James
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The proposed thesis will examine three areas of research: (1) the effects of hypoglycaemia on cognitive function in adults with and without T1DM, (2) the symptoms and awareness of hypoglycaemia in children and adolescents with T1DM and (3) hypoglycaemia and driving in people with insulin-treated diabetes: self-treatment and adherence to recommendations for avoidance. (1) Executive cognitive function governs organisation of thoughts, prioritisation of tasks, and time management. This study examined the effect of acute hypoglycaemia on executive function in adults with and without diabetes. Thirty-two adults with and without type 1 diabetes were studied. Two hyperinsulinaemic glucose clamps were performed at least 2 weeks apart in a single-blind, counterbalanced order. Executive functions were assessed with a validated test suite (Delis-Kaplan Executive Function). A general linear model (repeated-measures ANOVA) was used. Compared with euglycaemia, executive functions (with one exception) were significantly impaired during hypoglycaemia; lower test scores were recorded with more time required for completion. Large Cohen d values (>0.8) suggest that hypoglycaemia induces decrements in aspects of executive function with large effect sizes. In some tests, the performance of participants with diabetes was more impaired than those without diabetes. Executive cognitive function, which is necessary to carry out many everyday activities, is impaired during hypoglycaemia in adults with and without type 1 diabetes. (2) In children with type 1 diabetes mellitus (T1DM) the prevalence of impaired awareness of hypoglycaemia (IAH) is uncertain. Questionnaires were completed by 98 children with T1DM (mean age 10.6 years) and their parent(s); hospital admission data for the previous year were collected. Awareness of hypoglycaemia was assessed using two questionnaire-based methods that have been validated in adults. For 4 weeks, participants performed routine blood glucose measurements and completed questionnaires after each episode of hypoglycaemia. The ‘Gold’ questionnaire classified a greater proportion of the participants as having IAH than the ‘Clarke’ questionnaire (68.4 vs. 22.4%). Using the ‘Clarke’ method, but not the ‘Gold’ method, children with IAH were younger and more likely to require external assistance or hospital admission. In contrast to adults, behavioural symptoms were the best predictors of awareness status. IAH affects a substantial minority of children and impending hypoglycaemia may be heralded by behavioural symptoms. The ‘Clarke’ method was more effective at identifying those at increased risk. (3) A clinical survey of an outpatient clinic population to ascertain current knowledge and practice among drivers with insulin-treated diabetes. A representative sample of 202 current drivers with insulin-treated diabetes completed a structured questionnaire. A minimum blood glucose level of 4.0 mmol/L or higher was considered necessary for driving by 74.8%, and 87.1% reported always keeping carbohydrate in their vehicle. However, 38.1% reported never carrying a glucose meter when driving, and 59.9% that they never test blood glucose before driving, or test only if symptomatic of hypoglycaemia. Most participants 89% would stop driving to treat hypoglycaemia although only 13.9% would wait longer than 30 min. Compliance with statutory requirements to inform the licensing authority and motor insurer is good.