Hypoglycaemia in Type 2 diabetes

Abstract

The primary cause of hypoglycaemia in Type 2 diabetes is diabetes medication-in particular, those which raise insulin levels independently of blood glucose, such as sulphonylureas (SUs) and exogenous insulin. The risk of hypoglycaemia is increased in older patients, those with longer diabetes duration, lesser insulin reserve and perhaps in the drive for strict glycaemic control. Differing definitions, data collection methods, drug type/regimen and patient populations make comparing rates of hypoglycaemia difficult. It is clear that patients taking insulin have the highest rates of self-reported severe hypoglycaemia (25% in patients who have been taking insulin for > 5 years). SUs are associated with significantly lower rates of severe hypoglycaemia. However, large numbers of patients take SUs in the UK, and it is estimated that each year > 5000 patients will experience a severe event caused by their SU therapy which will require emergency intervention. Hypoglycaemia has substantial clinical impact, in terms of mortality, morbidity and quality of life. The cost implications of severe episodes-both direct hospital costs and indirect costs-are considerable: it is estimated that each hospital admission for severe hypoglycaemia costs around £1000. Hypoglycaemia and fear of hypoglycaemia limit the ability of current diabetes medications to achieve and maintain optimal levels of glycaemic control. Newer therapies, which focus on the incretin axis, may carry a lower risk of hypoglycaemia. Their use, and more prudent use of older therapies with low risk of hypoglycaemia, may help patients achieve improved glucose control for longer, and reduce the risk of diabetic complications. Diabet. Med. 25, 245-254 (2008)

Severe hypoglycaemia and cognitive impairment in older patients with diabetes: the Fremantle Diabetes Study

“…Patients in this category in the present sample were six times more likely to access health services for hypoglycaemia than those with greater BMI. This observation might be explained by insufficient energy intake for the prescribed blood glucose-lowering treatment and/or erratic meal patterns [9], but such detailed dietary data were not collected in the present study. Insulin treatment, a well recognised risk factor for severe hypoglycaemia in the elderly [8][9][10], increased the risk of future HSH three-fold in the present study and was also a strong risk factor for recurrent HSH.…”

“…Doctor verification All participants seen by study physicians for cognitive assessment were assessed using a checklist that included questions on history, frequency, symptoms [10] and severity of hypoglycaemia, and whether there was confirmation with blood glucose measurement below the normoglycaemic range (<3.5 mmol/l) [9]. The physician rated the accuracy of reports as proven, probable or uncertain.…”

“…Since the association between diabetes and cognitive impairment appears confined to middle-aged or older individuals [6], the ageing brain could be particularly susceptible to neuroglycopenia. The interpretation of studies examining the relationship between blood glucose-lowering therapies, hypoglycaemia and cognitive function in type 2 diabetes is, however, complicated by factors other than age, such as duration of diabetes and of insulin treatment, comorbidities, including renal insufficiency, and polypharmacy [7][8][9][10]. In addition, ascertainment of hypoglycaemia in older patients can be underestimated because of less distinctive symptoms [11].…”

“…In addition, ascertainment of hypoglycaemia in older patients can be underestimated because of less distinctive symptoms [11]. Cognitive impairment may itself lead to unreliable reporting of hypoglycaemia [12] and increase the risk of hypoglycaemia through medication errors and erratic meal patterns [9].…”

Changing the glucose cut-off values that define hypoglycaemia has a major effect on reported frequencies of hypoglycaemia

“…Obviously, standardised reporting of hypoglycaemia is desirable, but it has been argued that defining hypoglycaemia as any glucose value below 4.0 mmol/l may lead to overestimation of the frequency of (clinically significant) hypoglycaemia [2]. Plasma glucose falls below this level in health and exposure to glucose levels of 3.5-4.0 mmol/l is likely to be of little clinical significance [2].…”