Increasing Incidence of Pediatric Type 1 Diabetes Mellitus in Southeastern Wisconsin: Relationship with Body Weight at Diagnosis Jennifer Evertsen 1,2 *, Ramin Alemzadeh 3 , Xujing Wang 1 1 Departments of Epidemiology & Biostatistics Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America, 2 University of Wisconsin-Madison, Center for Urban Population Health, Milwaukee, Wisconsin, United States of America, 3 Department of Pediatrics, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America Abstract Introduction: Several studies have confirmed the increasing rate of type 1 diabetes mellitus (T1DM) in children and the link with increasing BMI at diagnosis termed the ‘accelerator hypothesis’. Our objective was to assess whether changing incidence of type 1 diabetes in a group of children and adolescent from the Midwest United States was associated with changes in BMI. Methods: Data from 1618 (52.1% M/47.9% F) newly-diagnosed children and adolescents (,19 years) with T1DM, admitted to Children’s Hospital of Wisconsin (CHW) between January 1995 and December 2004, was analyzed in relationship to body mass index (BMI) standard deviation score (SDS). Results: An overall, 10-year cumulative incidence of 27.92 per 100,000 (19.12 to 41.72/100,000) was observed, with an average yearly cumulative incidence of 2.39%. The increase was largest in the younger age groups, 0–4, 5–9, and 10–14 having an average yearly increase of 2.4, 2.3, and 3.0%, respectively, corresponding to a relative 10-year increase of 25.3, 33.8, and 38.0%, respectively. Age at diagnosis was inversely correlated with BMI SDS (p,0.001) and remained significant for both males and females. Conclusions: Annual incidence of T1DM increased two-fold at CHW over the 10-year study period. The majority of the increase was observed in the youngest age groups, which also appeared to be the heaviest. This research adds to the growing literature supporting the hypothesis that excess weight gain during childhood may be a risk factor for early manifestation of T1DM. Citation: Evertsen J, Alemzadeh R, Wang X (2009) Increasing Incidence of Pediatric Type 1 Diabetes Mellitus in Southeastern Wisconsin: Relationship with Body Weight at Diagnosis. PLoS ONE 4(9): e6873. doi:10.1371/journal.pone.0006873 Editor: Adrian Vella, Mayo Clinic College of Medicine, United States of America Received May 28, 2009; Accepted July 20, 2009; Published September 3, 2009 Copyright: ß 2009 Evertsen et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors have no support or funding to report. Competing Interests: The authors have declared that no competing interests exist. * E-mail: Jennifer.evertsen@aurora.org Introduction Type 1A diabetes mellitus (T1DM), an autoimmune disorder, accounts for 10% of diabetes diagnoses, affecting approximately 1.4 million people in the United States (US) and 10–20 million worldwide [1–3]. In the United States, 30,000 new cases occur annually and 40% of patients diagnosed are under the age of 20 [2–4]. Recently, studies suggest that the incidence of T1DM may be on the rise and increasing incidence in younger children is of the greatest concern. Incidence rates of pediatric T1DM vary widely throughout the world. Onkamo et al., (1999) reviewed pooled data from 37 studies (from 1960 to 1996), and observed an overall 2.8% to 3.0% per year global increase in incidence of T1DM [5]. However, only one study, by Kostraba et al., (1992) suggested a slightly negative, but not significant, trend in T1DM incidence in children and adolescents [6]. The World Health Organization’s DIAMOND study reported incidence rates from over 100 Centers ranging from 0.1/100,000 per year in China and Venezuela to 37.8/ 100,000 per year in Sardinia and 42.9/100,000 per year in Finland [2]. A large number of studies have been published supporting the rising incidence of T1DM, especially in the younger age groups [7–19]. One of the most notable and recent, in the United States, includes a population-based study of incidence rates of T1DM from 10 study locations by The SEARCH for Diabetes in Youth Study. The Search Group found an overall incidence of T1DM in children 0–19 of 24.3 per 100,000 person years with the highest rates observed among the 5–9 and 10–14 age groups with rates of 22.9 and 33.9 per 100,000 respectively [14]. There is still some speculation as to whether there is also an increase in incidence in the older adolescent groups. While the autoimmune nature of T1DM continues to be under investigation [20,21], the underlying mechanisms responsible for the rise of T1DM, especially in the younger age groups, remain unknown. However, the ‘‘accelerator hypothesis’’ proposed by Wilkin, is one of the more compelling theories [22–24]. This investigator suggested that increasing body weight in younger PLoS ONE | www.plosone.org 1 September 2009 | Volume 4 | Issue 9 | e6873