Type 1 Diabetes in the United Kingdom, 1995–2004

Abstract

To the Editor: Reported incidence rates (IR) of type 1 diabetes in the United Kingdom have reflected the high and rising rates seen in Northern Europe. We estimated the IR of type 1 diabetes by identifying newly-diagnosed cases of insulin-treated diabetes in children age 1-19 years for the years 1995-2004. Each case was required to have at least 6 months of recorded medical information prior to the date of diabetes diagnosis, with no prior treatment for or evidence of a diabetes diagnosis. We also conducted an age- and calendar-time matched case-control study comparing children with diabetes (cases) with children who were healthy (controls) to evaluate differences in medical history. The study was based on the General Practice Research Database that contains comprehensive electronic medical information from about 350 general practices during the past 20 years.1–3 After excluding cases with cystic fibrosis, we identified 1042 cases of incident diabetes during the 10-year study period. The population at risk for diabetes encompassed about 4.5 million children. The cumulative IR was 21/100,000 children, increasing by about 3% per year, primarily in children age 10-14 years. The IR rose progressively from about 5/100,000 for those age 1 year to 34/100,000 by age 12 years and fell to 15/100,000 by age 19 years (Fig.; eAppendix,http://llinks.lww.com). Overall, 29% of cases were hospitalized at the time of the diagnosis and 4% had ketoacidosis. The frequency of hospitalization at the time of the initial diagnosis fell from 42% in 1995-1996 to 23% in 2003-2006. In the year following diagnosis, 5% had an emergency room visit for hypoglycemia.FIGURE.: Incidence rate of type 1 diabetes by age at first diagnosis for the period 1995 to 2004.The frequencies of almost all nondiabetes-related-prescriptions and diagnoses were closely similar in patients with diabetes and healthy controls in the 31-365 days prior to diagnosis. An exception was thyroid hormone, which was prescribed in 18 cases (1.8%) compared with only 2 healthy controls (0.5%). Forty-nine percent of cases had at least one recorded medical visit in the 30 days prior to diagnosis compared with only 18% of calendar-matched controls. The frequency of medical visits prior to diagnosis was similar for cases and controls 31-365 days prior to the diagnosis date (eAppendix, http:/links.lww.com/EDE/A389). Celiac disease was diagnosed in 23 cases (0 controls) prior to age 20. All but 2 were diagnosed after the diabetes diagnosis had been made. The cumulative IR for type 1 diabetes (21/100,000) is consistent with the rate obtained in the United Kingdom as part of the EURODIAB study for years 1995-2003.4 Our observed increase of 3% per year is virtually identical to the one reported in that study; however that study reported that the increase was highest for children in the 0-4 year age group (4.8%) and lowest for the 10-14 year age group (2.1%).5 We observed the opposite trend, which suggests that a plateau effect, originally proposed by Gale,6 may have occurred in the youngest age group and a delayed increase may have occurred in children aged 10-14. This study provides additional population-based data on the incidence of type 1 diabetes in the United Kingdom from 1995-2004, including original results for those 15-19 years old at the time of diagnosis. The frequency of medical consultations was similar among diabetic and healthy children in the time period 31-365 days prior to the diagnosis date. By contrast, as might be expected, the consultation frequency was sharply higher among cases in the 30 days prior to the diagnosis date. This, together with the progressive fall in hospitalization frequency over time, provides evidence of increasingly prompt diagnosis of new-onset diabetes over this time period in United Kingdom. The current report also provides quantitative data on the previously suggested-associations of type 1 diabetes with hypothyroidism and celiac disease.6 ACKNOWLEDGMENTS We thank Edwin AM Gale for his comments and suggestions regarding the conduct and interpretation of this study and for his thoughtful review of the draft manuscript. Hershel Jick Katrina W. Hagberg Boston Collaborative Drug Surveillance Program Boston University School of Medicine Lexington, MA [email protected]