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

Context Little is 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 types 1 and 2 diabetes in relation to a high body mass index (BMI) in UK children and young adults. Design Cohort and nested case-control. Setting A total of 375 general practices that contribute to the UK Clinical Practice Research Datalink (CPRD). Participants A total of 369,362 participants aged 2 to 15 years at BMI measurement in CPRD from 1994 to 2013. Intervention None. Main outcome measures Incident type 1 diabetes (T1D) and type 2 diabetes (T2D) diagnoses up to age 25 years. Results A total of 654 incident cases of T2D and 1318 T1D cases were found. The incidence of T2D per 100,000 persons annually increased from 6.4 in 1994 to 1998 to 33.2 in 2009 to 2013; and that for T1D increased from 38.2 to 52.1 per 100,000 persons during the same period. The incidence of T2D increased in both overweight (85th to 95th percentile for age- and sex-specific BMI; P = 0.01) and obese (≥95th percentile; P < 0.01) individuals from 1994 to 2013. Obese individuals, who constituted 47.1% of T2D cases, had a markedly greater risk of incident T2D [odds ratio, 3.75; 95% confidence interval (CI), 3.07 to 4.57], with an incidence rate ratio of 4.33 (95% CI, 3.68 to 5.08) compared with the normal BMI category. No positive linear association was found between obesity (greater BMI) and incident T1D cases. Conclusions Increasing obesity has contributed to the increasing incidence of T2D but not T1D among UK children and young adults, with a fourfold greater risk of developing T2D in obese individuals.