The effects of glucose fluctuation on cognitive function and QOL: the functional costs of hypoglycaemia and hyperglycaemia among adults with type 1 or type 2 diabetes.

It is traditionally believed that while acute hypoglycaemia has detectable negative consequences, such as unpleasant symptoms and cognitive-motor disruptions, acute hyperglycaemia is not associated with such consequences. However, recent research with adults affected by either type 1 or 2 diabetes mellitus demonstrates that relatively mild hyperglycaemia is associated with unpleasant symptoms and cognitive disruptions. Both hyperglycaemia and hypoglycaemia can be associated with patient experiences of physical, affective, and cognitive symptoms, as well as cognitive-motor disruptions. These effects can lead to impaired functioning and quality of life. Because these effects are different across patients, their significance can be difficult to appreciate. There is ample evidence that acute hypoglycaemia is a problem for both adults with type 1 and those with type 2 diabetes, and that mild and moderate hypoglycaemia reduce one's mental efficiency relative to euglycaemic performance. There is growing evidence that transient hyperglycaemia has similar negative effects. At relatively mild levels of extreme blood glucose--either hypoglycaemia or hyperglycaemia--cognitive efficiency may decay by a third. The impact of this effect will depend on the task the patient is dealing with at the time. If the person is engaging in a relatively dangerous task, such as driving a vehicle, significant consequences could follow. Both hypoglycaemia and hyperglycaemia have been demonstrated to have not only acute, but also chronic effects in patients with type 1 as well as those with type 2 diabetes. Although hypoglycaemia occurs at a lower rate among patients with type 2 diabetes than among those with type 1, the number of patients with type 2 diabetes is so large that even this low rate results in many persons being affected.