Abstract

The potential of individuals with diabetes to develop hypoglycaemia during insulin treatment presents a possible risk to them and others in certain safety-critical tasks, such as driving. Restrictions for insulin-treated drivers may limit this risk, but the evidence upon which such restrictions are based is limited. Prior epidemiological and pathophysiological evidence suggests that individuals with Type 2 diabetes in the early stages of insulin treatment may be: • at no greater risk of hypoglycaemia than individuals with Type 2 diabetes treated with sulphonylureas • prone to less severe or less frequent periods of hypoglycaemia compared people with Type 1 diabetes. 1. We have conducted a prospective study, measuring the frequency and type of hypoglycaemia in different groups of individuals with diabetes to test these two hypotheses. This study, reported here, used self-reported hypoglycaemia (measured by questionnaires) and continuous glucose monitoring to record episodes of hypoglycaemia over 9–12 months in the following groups: • Type 1 diabetes of short duration (diagnosed within the past 5 years) • Type 1 diabetes of long duration (on insulin for more than 15 years) • Type 2 diabetes – tablet-treated (using sulphonylurea treatment) • Type 2 diabetes recently started on insulin (treated with twice-daily insulin for less than two years) • Type 2 diabetes on insulin of long duration (taking insulin for over 5 years). 2. There were no significant differences in median rates of low interstitial glucose (LIG) (measured by continuous glucose monitoring) or in rates of self-reported mild or severe hypoglycaemia in those with Type 2 diabetes treated with sulphonylureas when compared to patients with Type 2 diabetes started on insulin over the previous two years. 3. Episodes of hypoglycaemia and LIG in those with Type 1 diabetes of short duration were generally more frequent (with median rates around 10 fold higher in some categories) than in those with Type 2 diabetes recently started on insulin. 4. It was not possible to find risk factors which could conclusively predict hypoglycaemic risk during the period of monitoring. However, the C-peptide level (which measures the capacity of the body to release insulin) was identified as a clinical marker with potential utility as a predictor of hypoglycaemic episodes and worthy of further investigation. 5. We conclude that initiating insulin treatment in individuals with Type 2 diabetes is not necessarily associated with an increased risk of hypoglycaemia in the early stages, compared with that of individuals treated with sulphonylureas.