Accurate contemporary estimates of life expectancy among patients with type 1 diabetes would be useful as a summary measure of the current effect of diabetes, as a benchmark for assessing changes in diabetes care through time, and for the setting of insurance premiums. Although there are many reports of the standardized mortality ratios for type 1 diabetes, few studies have provided life expectancy data. Diabetes charities such as Diabetes UK and the Juvenile Diabetes Research Foundation cite losses of life expectancy of between 15 and 20 years.^1,2 Estimates from the United States in the 1970s reported a loss of 27 years.³ A report from 431 patients in New Zealand with type 1 diabetes during the 1980s found a loss of 16.5 years.⁴ In contrast, a recent analysis based on 325 deaths in participants in the Pittsburgh Epidemiology of Diabetes Complications (EDC) study⁵ estimated a loss of only 4 years for those diagnosed after 1965 but used extrapolation for older ages because the cohort had few people who had attained older ages.

Hypoglycaemia has long been recognised as a dangerous side-effect of treatment of diabetes with insulin or insulin secretagogues. With its potential to disrupt cerebral function, hypoglycaemia can have a major effect on peoples' lives. Study findings have suggested that hypoglycaemia is associated with an increased risk of cardiovascular events and mortality. Different mechanisms by which hypoglycaemia might provoke cardiovascular events have been identified in experimental studies, and in clinical studies cardiac arrhythmias have been reported to be induced by hypoglycaemia, with one report describing sudden death during a severe episode. Emerging evidence suggests that the association between hypoglycaemia and cardiovascular events and mortality is likely to be multifactorial. The association is probably partly caused by confounding, with hypoglycaemia occurring more frequently in people with comorbidities who are also more likely to die than those without. However, people with type 1 or type 2 diabetes also seem at risk of hypoglycaemia-induced cardiovascular effects. This risk should be recognised by clinicians when agreeing glycaemic goals with patients and choosing appropriate glucose-lowering therapies.