Confirmation of altered hypoglycaemia awareness by structured questionnaire and continuous ambulatory glucose profiles in those with Type 1 diabetes mellitus complicated by severe hypoglycaemia
RM Thomas, N Leech & JAM Shaw
Objectives: To define clinical and metabolic factors associated with severe hypoglycaemia (SH) in affected individuals with Type 1 diabetes (T1DM).
Methods: Individuals with T1DM and SH (defined as hypoglycaemia requiring third party intervention within the preceding 12 months) were characterised to include screening for other underlying autoimmune disease (coeliac serology, short synacthen and thyroid function tests); a questionnaire to evaluate underlying altered hypoglycaemia awareness; and ambulatory continuous subcutaneous glucose profile (CGMS).
Results: 29 individuals (20(69%) male) were recruited with mean age 41 years; diabetes duration 23 years; BMI 26 kilogram per m 2; HbA1C 8.8(6.6-15.7)% and insulin dose/bodyweight 0.74 Units per kilogram. 25(86%) were on a basal bolus regime. Lipohypertrophy was present in 6 (20%). 6(21%) had known thyroid disease. A single new diagnosis of coeliac disease was made. 4 (14%) had experienced >10 episodes of SH over the preceding 12 months; 23(79%) 5-10 episodes; 2 (7%) 0-4 episodes. 18(62%) had lost previous symptoms of hypoglycaemia with 2(17%) describing no remaining symptoms. 8(27%) stated they could never tell from symptoms that blood glucose level may be low. 3(10%) felt they could always tell. Blood glucose level at which symptoms occurred was stated as <3.2mmol/L in 24(83%) and <2.2mmol/l in 12(41%). This level had changed since diabetes diagnosis in 22(75%). Mean length of CGMS profiles was 5 days. Overnight (2400-0600hr): individuals spent a mean of 72minutes every night with glucose <4mmo/l (30minutes <2.2mmol/l). During each day (0600-2400hr): mean duration <4mmol/l was 168minutes (42minutes<2.2mmol/l). 86% of nocturnal and 76% of daytime episodes were asymptomatic with 93% and 72% respectively undetected by routine blood glucose monitoring.
Conclusions: Altered hypoglycaemia awareness confirmed by questionnaire and prolonged asymptomatic hypoglycaemia on CGMS profile has been demonstrated in individuals with T1DM complicated by SH. Employment of a structured questionnaire may enable identification of those at risk of SH.