Body Mass Index and Incident Type 1 and Type 2 Diabetes in Children and Young Adults: A Retrospective Cohort Study

Context: There is little known about the association between obesity and temporal trends in the incidence of diabetes in children and young adults. Objective: We examined the recent incidence of type 1 diabetes and type 2 diabetes (T2D) in relation to high body mass index (BMI) in children and young adults. Design: Cohort and nested case-control. Setting: 375 general practices that contribute to the UK Clinical Practice Research Datalink (CPRD). Participants: 369,362 participants aged 2-15 years old at BMI measurements in CPRD between 1994 and 2013. Intervention: None. Main outcome measures: Incident T1D andT2D Results: There were 654 incident cases of T2D and 1318 T1D cases. The incidence of T2D per 100,000 persons per year increased from 6.4 in 1994-8 to 33.2 in 2009-13; that for T1D increased from 38.2 to 52.1 per 100,000 over the same period. The incidence of T2D increased in both overweight (85th-95th percentile for age- and sex-specific BMI; P=0.01) or obese (≥95th percentile; P<0.01) individuals from 1994 to 2013. Obese individuals, who constituted 47.1% of T2D cases, had a markedly higher risk of incident T2D (odds ratio, 3.75[95%CI, 3.07-4.57]) with an incidence rate ratio of 4.33 (95%CI, 3.68-5.08), compared with normal BMI category. There was no positive linear association between obesity (higher BMI) and incident T1D. Conclusion: Increasing obesity is contributing to the rising incidence of T2D, but not T1D, among UK children and young adults, with a four-fold greater risk of developing T2D in those who are obese.