020 Incidence rate trends in childhood type 1 diabetes in Yorkshire, 1978-2007: effects of ethnicity and age at diagnosis

Abstract

Objective To examine incidence rates and trends of childhood Type 1 diabetes in Yorkshire from 1978 to 2007. Methods Data from the population-based Yorkshire Register of Diabetes in Children and Young People was used to analyse the incidence of Type 1 diabetes in children aged <15 years diagnosed in the former Yorkshire Regional Health Authority. Incidence rates (per 100 000 per year) were estimated using mid-year population estimates stratified by sex, age and ethnicity: south Asian (Indian, Pakistani, Bangladeshi) or non-south Asian (all other ethnicities). Ethnicity was assigned using two name recognition programs (Nam Pehchan and SANGRA) and a local expert. Age-sex standardised rates were calculated between 1978 and 2007 and by ethnic-group between 1990 and 2007. Poisson regression was used to assess incidence trends and estimate predicted rates up to 2020. Goodness-of-fit, AIC and likelihood-ratio tests were used to assess model fit. Results 3896 children were diagnosed in Yorkshire between 1978 and 2007. Overall incidence was 18.1 (95% CI 17.5 to to 18.6), increasing from 13.3 (1978 to 1987) to 16.9 (1988 to 1997) to 24.1 (1998 to 2007). Incidence increased significantly over time: average annual percentage change (AAPC) was 2.8% (1.8 to 3.8). The inclusion of an age-sex interaction term provided evidence for differences in trends between sexes depending on age, with females having higher incidence and AAPC than males for those aged 5–9. Overall incidence for non-south Asians (21.4; 20.6 to 22.3) was significantly higher than that of south Asians (14.6; 12.3 to 17.0) over the entire study period. A significant increasing trend in incidence was observed for non-south Asians of 3.3% (1.3 to 5.2) compared to a non-significant trend seen in south Asians (1.9%; –0.4 to 4.3). Overall forecasted incidence for 2020 is 38.3 per 100 000. Conclusions Type 1 diabetes incidence rates have risen almost uniformly for non-south Asians of all ages but not for south Asians, contrary to findings in the Bradford area of Yorkshire between 1978 and 1998. Overall incidence increased most quickly in the 5–9 age-group. Incidence doubled from 12.5 to 25.2 between 1978 and 2007. If current trends continue, rates will rise by 52% to 38.3 between 2007 and 2020.