AGE-PERIOD-COHORT ANALYSIS OF 1990-2003 INCIDENCE TIME TRENDS OF CHILDHOOD DIABETES IN ITALY: THE RIDI STUDY
- Graziella Bruno, MD ()1,
- Milena Maule, MD2,
- Franco Merletti, MD2,
- Giulia Novelli, MD1,
- Alberto Falorni, MD3,
- Antonio Iannilli, MD4,
- Lorenzo Iughetti, MD5,
- Emma Altobelli, MD6,
- Giuseppe d'Annunzio, MD7,
- Silvano Piffer, MD8,
- Paolo Pozzilli, MD9,
- Dario Iafusco, MD10,
- Marco Songini, MD11,
- Federico Roncarolo, MD12,
- Sonia Toni, MD13,
- Flavia Carle, MD14,
- Valentino Cherubini, PhD4 and
- RIDI Study Group
- 1Dept. of Internal Medicine, University of Turin, Italy
- 2Cancer Epidemiology Unit, CeRMS and CPO Piemonte, University of Turin, Italy
- 3Dept. of Internal Medicine, University of Perugia, Italy
- 4Dept. of Pediatrics, Polytechnic University of Marche, Ancona, Italy
- 5Dept. of Pediatrics, University of Modena, Italy
- 6Dept. of Epidemiology, University of L'Aquila, Italy
- 7Dept. of Pediatrics, University of Genova, Italy
- 8Unit of Observational Epidemiology, Trento, Italy
- 9Università Campus Bio_Medico, University of Rome, Italy
- 10Dept. of Pediatrics, University of Napoli, Italy
- 11S. Michele Hospital, Cagliari, Italy
- 12Dept. of Preventive Medicine, University of Pavia, Italy
- 13Dept. Of Pediatrics, University of Florence, Italy
- 14Dept. of Epidemiology, Biostatistics and Medical Information Technology, Polytechnic University of Marche, Ancona, Italy
Objective: to investigate age-period-cohort effects on temporal trend of type 1 diabetes in age 0-14 years in Italian registries.
Research Design and Methods: This report is based on 5180 incident cases in the period 1990-2003. Multilevel (random intercept) Poisson regression models have been used to model the effects of sex, age, calendar time and birth cohorts on temporal trends taking into account the registry-level variance component.
Results: The incidence rate was 12.26 per 100,000 person-year, significantly higher in boys (13.13; 95% confidence interval (CI): 12.66-13.62) than in girls (11.35; CI: 10.90-11.82). Large geographical variations in incidence within Italy were evident, being highest in Sardinia, intermediate in Central-Southern Italy, and high in Northern Italy, particularly in the Trento Province, where an incidence rate of 18.67/100,000 was registered. An increasing temporal trend was evident (2.94% per year, CI 2.22-3.67). With respect to the calendar period 1990-92, the incidence rates increased linearly, being 15%, 27%, 35% and 40% higher in the following time periods (p for trend <0.001). With respect to the birth cohort 1987-1993, the incidence rate ratio increased approximately linearly from 0.63 (CI 0.54-0.73) in the cohort 1975-81 to 1.38 (CI 1.06-1.80) in the cohort 1999-2003. The best model, however, was the one with sex, age and a linear time trend (drift).
Conclusions: Large geographical variations and an increasing temporal trend are evident in Italy. Age period-cohort analysis shows that the variation over time has a linear component that cannot be ascribed to either the calendar period or the birth cohort.
- Received January 31, 2010.
- Accepted June 10, 2010.
- Copyright © American Diabetes Association