A population-based study of risk factors for severe hypoglycaemia in a contemporary cohort of childhood-onset type 1 diabetes
Matthew N. Cooper
Susan M. O'Connell
Elizabeth A. Davis
Timothy W. Jones
0
) Telethon Institute for Child Health Research, Centre for Child Health Research, The University of Western Australia
,
Perth, WA
,
Australia
Aims/hypothesis Severe hypoglycaemia is a major barrier to optimising glycaemic control. Recent changes in therapy, however, may have altered the epidemiology of severe hypoglycaemia and its associated risk factors. The aim of this study was to examine the incidence rates and risk factors associated with severe hypoglycaemia in a contemporary cohort of children and adolescents with type 1 diabetes. Methods Subjects were identified from a population-based register containing data on >99% of patients (<16 years of age) who were being treated for type 1 diabetes in Western Australia. Patients attend the clinic approximately every 3 months, where data pertaining to diabetes management, demographics and complications including hypoglycaemia are prospectively recorded. A severe hypoglycaemic event was defined as an episode of coma or convulsion associated with hypoglycaemia. Risk factors assessed included age, duration of diabetes, glycaemic control, sex, insulin therapy, socioeconomic status and calendar year.
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Abbreviations
BD Twice-daily insulin injection
CSII Continuous subcutaneous insulin infusion
IRR Incidence risk ratio
MDI Multiple-daily insulin injection
SEIFA Index of relative socioeconomic disadvantage
The threat of hypoglycaemia as a consequence of insulin
treatment is the single most important barrier to optimising
glycaemic control in type 1 diabetes [1, 2]. The major
challenge for clinicians treating children and adolescents is to
optimise glycaemic control whilst avoiding hypoglycaemia.
Fear of hypoglycaemia can have a negative impact on quality
of life [3, 4] and metabolic control [5, 6], which can be
detrimental to achieving improved glycaemic control. The
Diabetes Control and Complications Trial showed that
intensive management resulted in a significant increase in
episodes of severe hypoglycaemia [7, 8]. Similarly, in the
early 1990s, at our centre, increased emphasis on optimising
glycaemic control was paralleled by an increase in the rate of
severe hypoglycaemia, particularly in younger children
(<6 years) [1, 9]. In three previous publications we have
reported rates of, and associations with, severe hypoglycaemia
in a population-based sample of children and adolescents with
type 1 diabetes [1, 3, 10]. In those reports, we found that an
increased risk of severe hypoglycaemia was associated with
younger age (<6 years), lower HbA1c, higher insulin dose,
male sex, longer duration of diabetes and lower parental
socioeconomic status.
Increasingly, evidence is emerging that rates of severe
hypoglycaemia may be reducing [3, 11, 12]. This may have
resulted from improvements in therapy [13], suggesting that
re-evaluation of the factors associated with severe events
may be required. As a follow-up to the previously published
analysis [1, 10] and a subsequent update of rates of severe
hypoglycaemia [3], our objectives for this study were to
characterise the current epidemiology of, and risk factors
for, severe hypoglycaemia in a contemporary child and
adolescent population-based cohort.
All children and adolescents with type 1 diabetes aged 18 years
attending the diabetes clinic at Princess Margaret Hospital for
Children from 2000 to 2011 inclusive participated in the study.
The Department of Endocrinology and Diabetes is the only
paediatric referral centre for diabetes in the state of Western
Australia (2012 population 2.4 million [14]). The case
ascertainment for this centre has previously been shown to be 99.9%
for children diagnosed at <16 years of age [15]. Consent for
data to be entered into the database was obtained from all
parents or guardians, and data collection was approved by the
institutions ethics committee.
All patients attending the centre are managed by a
multidisciplinary diabetes care team, which includes a paediatric
diabetologist, diabetes nurse educator, dietitian, social
worker and psychologist. Education for recognition and treatment
of hypoglycaemia, and preventive measures for special
circumstances such as participation in exercise, is routine. The
patients and their family were advised to keep a logbook of
blood glucose levels and insulin doses, and to record all
adverse or atypical events such as episodes of hypoglycaemia
or illness. They were taught to obtain a blood glucose level, if
possible, to confirm hypoglycaemia. They were seen in the
clinic approximately every 3 months, and data on all diabetes
outcomes including hypoglycaemic events and treatment
types were prospectively recorded in the Western Australian
Childhood Diabetes Database, as has been described in our
past reports. Subjects exited the study upon turning 18 years,
leaving the state permanently or if 12 months had lapsed
following their last clinic visit. HbA1c was determined at each (...truncated)