Hypoglycaemia in Clinical Diabetes

58 FREQUENCY, CAUSES AND RISK FACTORS15Recalled severe hypoglycaemia(episodes per patient-year)10500 5 10 15Prospectively recorded severe hypoglycaemia(episodes per patient-year)Figure 3.2 Correlation between prospectively recorded and retrospectively recalled rate of severehypoglycaemia over the same one year period in 230 people with type 1 diabetes. Marker sizes areweighted by the number of cases. R 2 = 066; p < 0001. Reproduced with permission from Pedersen-Bjergaard et al. (2003b) © John Wiley & Sons, Ltdin the study by Pramming et al., (1991) was much lower, but the period of follow up wasonly one week. This skewed distribution serves to emphasise further the importance ofpatient selection in ascertaining the frequency of severe hypoglycaemia with accuracy, as theexclusion of a relatively small number of people at high risk would substantially reduce theoverall risk.In three of the studies of unselected adults with type 1 diabetes, severe hypoglycaemia wasfurther subdivided to examine episodes associated with more significant neuroglycopenia,i.e., those resulting in coma and/or seizures (Table 3.2) (ter Braak et al., 2000; Pedersen-Bjergaard et al., 2003a; Pedersen-Bjergaard et al., 2004). Furthermore, in the study byMuhlhauser et al., (1998) only episodes treated with intra-muscular glucagon or intravenousglucose were addressed. Predictably, such events were rarer and represented about onequarter of all episodes of severe hypoglycaemia.Emergency and hospital services will occasionally be involved in the management ofsevere hypoglycaemia and there are data on the use of such agencies. This clearly hasto be interpreted with caution, as the majority of all hypoglycaemia is managed in thecommunity, without involvement of (para)clinical staff. Individuals admitted to hospitalwith hypoglycaemia are probably atypical, and have an increased prevalence of alcoholdependence and mental illness (Hart and Frier, 1998). An early study from Australia reportedthat, over one year, 3.5% of people attending an urban diabetes clinic had an episode ofhypoglycaemia severe enough to warrant referral to hospital (Moses et al., 1985). Morerecent data from Tayside, Scotland, demonstrated that 7.1% of people with type 1 diabetes