Effects of Acute Hypoglycemia on Cognitive Function in T1DM
Effects of Acute Hypoglycemia on Cognitive Function in T1DM
Throughout life with type 1 diabetes mellitus people with the condition are exposed to multiple episodes of hypoglycaemia associated with insulin therapy. Hypoglycaemia affects several domains of cognitive function. Studies in non-diabetic adults and in people with type 1 diabetes have shown that almost all domains of cognitive function are impaired to some degree during acute hypoglycaemia, with complex tasks being more greatly affected.
The specific cognitive functions of attention and memory are both profoundly impaired during hypoglycaemia. These cognitive processes are fundamental to the performance of many day to day tasks. Their impairment disrupts everyday life and raises safety concerns for the pursuit of activities such as driving.
Mood and emotion are also negatively affected by hypoglycaemia, resulting in tense tiredness, while motivation is reduced, and anger may be generated in some individuals. Hypoglycaemia can cause embarrassing social situations, and may lead to chronic anxiety and depression in people with type 1 diabetes.
At present few therapeutic measures can modify or ameliorate the effects of hypoglycaemia on cognitive function, so instigation of measures to prevent exposure to hypoglycaemia is of major clinical importance, while preserving good glycaemic control.
Cognitive function refers to all aspects of thinking and intellectual activity. This encompasses many mental processes: abstract thinking, reasoning, judgement, language, memory, attention and concentration, motor performance, constructional ability, speed of information processing and perception. Earlier studies of hypoglycaemia that used tests of general cognitive function found that most were affected adversely (Table 1).
Simple cognitive tasks such as finger tapping and simple reaction time are not significantly affected by hypoglycaemia, but the speed at which tasks are performed is often diminished, while accuracy or absolute ability are preserved. More recent research has tried to isolate specific cognitive processes, but this is difficult to achieve as most psychometric tests and everyday tasks require a combination of cognitive skills, so attempting segregation into separate cognitive domains is difficult and artificial.
Testing cognitive function during hypoglycaemia has several limitations, and many studies differ too much in design and methodology to permit comparison of results. Target blood glucose levels vary from 2 to 3 mmol/l, and measures of cognitive function include a wide range of tests and some neurophysiological measures such as sensory evoked potentials. Study design may be inadequate through lack of a euglycaemia control arm, an absence of power calculations and heterogeneity of study cohorts. It is often difficult to extrapolate experimental outcomes to real life scenarios where blood glucose excursions may be more rapid and hypoglycaemia less prolonged. Exposure to hypoglycaemia is not confined to the young and healthy, who are the usual participants in research studies; older people may respond differently or experience greater magnitudes of dysfunction.
1. Abstract and Introduction
Abstract
Throughout life with type 1 diabetes mellitus people with the condition are exposed to multiple episodes of hypoglycaemia associated with insulin therapy. Hypoglycaemia affects several domains of cognitive function. Studies in non-diabetic adults and in people with type 1 diabetes have shown that almost all domains of cognitive function are impaired to some degree during acute hypoglycaemia, with complex tasks being more greatly affected.
The specific cognitive functions of attention and memory are both profoundly impaired during hypoglycaemia. These cognitive processes are fundamental to the performance of many day to day tasks. Their impairment disrupts everyday life and raises safety concerns for the pursuit of activities such as driving.
Mood and emotion are also negatively affected by hypoglycaemia, resulting in tense tiredness, while motivation is reduced, and anger may be generated in some individuals. Hypoglycaemia can cause embarrassing social situations, and may lead to chronic anxiety and depression in people with type 1 diabetes.
At present few therapeutic measures can modify or ameliorate the effects of hypoglycaemia on cognitive function, so instigation of measures to prevent exposure to hypoglycaemia is of major clinical importance, while preserving good glycaemic control.
Introduction
Cognitive function refers to all aspects of thinking and intellectual activity. This encompasses many mental processes: abstract thinking, reasoning, judgement, language, memory, attention and concentration, motor performance, constructional ability, speed of information processing and perception. Earlier studies of hypoglycaemia that used tests of general cognitive function found that most were affected adversely (Table 1).
Simple cognitive tasks such as finger tapping and simple reaction time are not significantly affected by hypoglycaemia, but the speed at which tasks are performed is often diminished, while accuracy or absolute ability are preserved. More recent research has tried to isolate specific cognitive processes, but this is difficult to achieve as most psychometric tests and everyday tasks require a combination of cognitive skills, so attempting segregation into separate cognitive domains is difficult and artificial.
Testing cognitive function during hypoglycaemia has several limitations, and many studies differ too much in design and methodology to permit comparison of results. Target blood glucose levels vary from 2 to 3 mmol/l, and measures of cognitive function include a wide range of tests and some neurophysiological measures such as sensory evoked potentials. Study design may be inadequate through lack of a euglycaemia control arm, an absence of power calculations and heterogeneity of study cohorts. It is often difficult to extrapolate experimental outcomes to real life scenarios where blood glucose excursions may be more rapid and hypoglycaemia less prolonged. Exposure to hypoglycaemia is not confined to the young and healthy, who are the usual participants in research studies; older people may respond differently or experience greater magnitudes of dysfunction.
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