Clinical characteristics at onset of Type 1 diabetes in children diagnosed between 1977 and 2001 in the south-east region of Sweden

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Abstract

To survey clinical characteristics at diagnosis for children diagnosed with Type 1 diabetes during 25 years in the south-east part of Sweden we included all 1903 children <16 years of age and who had been diagnosed between 1977 and 2001 in the south-east region of Sweden. A nurse or doctor in the diabetes team obtained information from medical records.

Over the 25 years the mean duration of symptoms prior to diagnosis was 17.8 ± 26.4 days and the mean glucose level at diagnosis was 23.6 ± 9.7 mmol/l. Three percent of the children (n = 50) had a pH value ≤ 7.1. The youngest children (0–5 years) had shorter duration of symptoms, lower blood-glucose levels and less often had ketonuria than the oldest children (11–15 years) but more often suffered from infections prior to diagnosis. The proportion of children diagnosed in the group 0–5 years of age increased over the study-period, apart from the last 5 years, while children with pH value ≤ 7.3 decreased significantly as did the proportion of children with ketonuria or infection.

The clinical characteristics at diagnosis of diabetes are heterogeneous, especially in the oldest age group. Some characteristics varied with time.

Introduction

Type 1 diabetes is a heterogeneous disease where genetic and environmental factors as well as autoimmune mechanisms are involved [1], [2]. There are differences in the expression and course of the disease related to age [3], genetic background [4], [5] and season of onset [6], [7], but also in the clinical characteristics at diagnosis [8], [9]. One group of patients are more often diagnosed during incidence peaks, have a short duration of symptoms and often have infection prior to diagnosis [10], [11]. Another group of patients are those diagnosed throughout the year, have a more gradual onset and perhaps also a longer remission period [12], [13].

There seem to be differences in the clinical manifestations at onset of the disease between areas with high incidence and areas with low incidence [14], [15]. Some studies have also found that the clinical presentation has become less severe with time [16], [17], while others have not found this [18].

We have previously demonstrated that children in south-east Sweden are sometimes diagnosed in space-time clusters [19] and that there is a difference in birth pattern amongst children who later develop diabetes compared to the background population [20].

In the present study we surveyed clinical characteristics at diagnosis for all children <16 years of age with Type 1 diabetes diagnosed between 1977 and 2001 at seven paediatric clinics in south-east of Sweden. The aims were: (1) to analyse clinical characteristics in the whole group, (2) to explorer gender distribution, (3) to investigate if there were any time trends regarding these characteristics, and finally (4) to see if there were any differences between paediatric clinics in the region.

Section snippets

Patients and methods

In the Swedish health-care system, all children up to 16 years of age with diabetes are treated at pediatric clinics. From the seven pediatric clinics in south-east Sweden we included all 1903 children <16 years of age who had been diagnosed, according to WHO's criteria and definition, with Type 1 diabetes between 1977 and 2001 (Table 1). The children were born between 1962 and 2000. The catchment areas of these clinics form a continuous geographical region of 42,356 km2 which during 1977 and

Laboratory methods

Blood glucose was measured (n = 1872, completeness 98%) using the standard glucose peroxidase reaction at the laboratories of the hospitals involved. The highest blood glucose value during the 24 h prior to the first insulin injection was included in the analysis. HbA1c was measured before the first insulin injection or within one week of the injection using the DCA-2000 analyser (Bayer Diagnostics) and adjusted to a national standard which gives values about 1% lower than the DCCT standard [21]

Statistical analysis

Statistical analysis was performed using χ2 (crosstabs), two-tailed Student's t-test, and one way analysis of variance (ANOVA). When the distribution was skewed, we also purposed Mann–Whitney U-test or Kruskal–Wallis tests. In the analysis we used the statistical package for Social Sciences for Windows (SPSS-WIN). The results are expressed as mean ± S.D.

Ethics

The study was approved by the Ethics Committee of the faculty of health sciences, Linköping University.

Subjects

Between 1977 and 2001, Type 1 diabetes was diagnosed in 1903 children under 16 years of age in the region. There were 1031 boys and 872 girls. Twenty-four percent (456 children, 254 boys) were between 0 and 5 years of age at diagnosis, 37% (700, 362 boys) were between 6 and 10 years, and 39% (742, 415 boys) were between 11 and 15 years of age.

Clinical characteristics

The mean duration of common symptoms (thirst, polyuria and weight loss) before diagnosis was 17.8 ± 26.4 days, with the oldest age group having the

Discussion

In the Swedish health-care system all children upto 16 years of age with diabetes attend paediatric departments. We are therefore confident that all children with newly diagnosed diabetes in the study area are included.

In the present study the mean glucose level at onset was comparable with levels reported by others [9], [22], while the proportion of children with ketonuria at onset was lower [9], [22], [23]. The same pattern was found regarding mild and severe ketoacidosis, the incidences of

Acknowledgements

We are grateful to the nurses and doctors in charge of diabetes care at the paediatric departments in Jönköping, Kalmar, Karlskrona, Linköping, Norrköping, Västervik, and Växjö for providing patient data. Funding: This study was supported by the Swedish Child Diabetes Foundation (Barndiabetesfonden) and FORSS (Research council in south-east Sweden).

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