Incidence of Type 1 and Type 2 Diabetes in Adults Aged 30–49 Years

• Published in: Diabetes care Vol. 28; no. 11; pp. 2613 - 2619
• Main Authors: Bruno, Graziella, Runzo, Cristina, Cavallo-Perin, Paolo, Merletti, Franco, Rivetti, Marina, Pinach, Silvia, Novelli, Giulia, Trovati, Mariella, Cerutti, Franco, Pagano, Gianfranco
• Format: Journal Article
• Language: English
• Published: American Diabetes Association 01.11.2005
• ISSN: 0149-5992; 1935-5548; 1935-5548
• DOI: 10.2337/diacare.28.11.2613

Incidence of Type 1 and Type 2 Diabetes in Adults Aged 30–49 Years The population-based registry in the province of Turin, Italy Graziella Bruno , MD 1 , Cristina Runzo , MD 1 , Paolo Cavallo-Perin , MD 1 , Franco Merletti , MD 2 , Marina Rivetti , MD 1 , Silvia Pinach , PHD 1 , Giulia Novelli , MD 1 , Mariella Trovati , MD 3 , Franco Cerutti , MD 4 , Gianfranco Pagano , MD 1 and for the Piedmont Study Group for Diabetes Epidemiology * 1 Department of Internal Medicine, University of Turin, Turin, Italy 2 Unit of Cancer Epidemiology, CERMS and Center for Oncologic Prevention, University of Turin, Turin, Italy 3 Department of Clinical and Biological Sciences, Diabetes Unit, University of Turin, Turin, Italy 4 Department of Pediatrics, University of Turin, Turin, Italy Address correspondence and reprint requests to Dr. Graziella Bruno, Department of Internal Medicine, University of Turin; corso Dogliotti 14, I-10126 Turin, Italy. E-mail: graziella.bruno{at}katamail.com Abstract OBJECTIVE —Incidence of type 1 diabetes is considered to be low in adults, but no study has been performed in Mediterranean countries. RESEARCH DESIGN AND METHODS —We extended the study base of the registry of the province of Turin, Italy, to subjects aged 30–49 years in the period 1999–2001 to estimate the incidences of type 1 and type 2 diabetes. Diagnosis of type 1 diabetes was based on permanent insulin treatment or a fasting C-peptide level ≤0.20 nmol/l or islet cell (ICA) or GAD (GADA) antibody positivities. RESULTS —We identified 1,135 case subjects with high completeness of ascertainment (99%), giving an incidence rate of 58.0 per 100,000 person-years (95% CI 54.7–61.5). The incidence of type 1 diabetes was 7.3 per 100,000 person-years (6.2–8.6), comparable with the rates in subjects aged 0–14 and 15–29 years (10.3 [9.5–11.2] and 6.8 [6.3–7.4]). Male subjects had a higher risk than female subjects for both type 1 (rate ratio [RR] 1.70 [95% CI 1.21–2.38]) and type 2 (2.10 [1.84–2.40]) diabetes. ICA and/or GADA positivities were found in 16% of the cohort. In logistic regression, variables independently associated with autoimmune diabetes were age 30–39 years (odds ratio [OR] 2.39 [95% CI 1.40–4.07]), fasting C-peptide <0.60 nmol/l (3.09 [1.74–5.5]), and BMI <26 kg/m 2 (2.17 [1.22–3.85]). CONCLUSIONS —Risk of type 1 diabetes between age 30 and 49 years is similar to that found in the same area between age 15 and 29 years. Further studies are required to allow geographical comparisons of risks of both childhood and adulthood autoimmune diabetes, the latter being probably higher than previously believed. GADA, GAD antibody ICA, islet cell antibody Footnotes * ↵ * Members of the Piedmont Study Group for Diabetes Epidemiology can be found in the appendix . A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. Accepted July 30, 2005. Received March 13, 2005. DIABETES CARE