Rising incidence of insulin dependent diabetes in children aged under 5 years in the Oxford region: time trend analysis

Objectives: To monitor incidence of insulin dependent diabetes in children in Oxford health region since 1985, and to look for any evidence of disproportionate increase in children aged under 5, Design: Primary ascertainment of cases of childhood diabetes was by prospective registration of all patients with insulin dependent diabetes diagnosed before age 15 years between 1985 and 1996 and resident in Oxford region at time of diagnosis, This was supplemented by examination of centralised hospital discharge records and death certificates, Secondary case ascertainment was by postal surveys of general practitioners in 1987 and 1996, Setting: Area formerly administered by Oxford Regional Health Authority. Subjects: 1037 children presenting with insulin dependent diabetes under age of 15 years, Main outcome measures: Incidence of insulin dependent diabetes in children aged 0-4, 5-9, and 10-14 years during 1985-95, Results: Overall incidence of diabetes in children aged 0-15 was 18.6 cases/100 000/year and showed an annual increase of 4% from 1985 to 1996. This was mainly due to a rapid increase in children aged 0-4 years, in whom there was an annual increase of 11% (95% confidence interval 6% to 15%, P < 0.0001), while the annual increase in those aged 5-9 was 4% (0 to 7%, P = 0.05) and in those aged 10-14 was 1% (-2% to 4%, P = 0.55), Conclusions: Incidence of insulin dependent diabetes in children aged under 5 years has risen markedly in the Oxford region over the past decade, The cause of the increase is unknown, but environmental influences encountered before birth or in early postnatal life are likely to be responsible.