AGE-PERIOD-COHORT ANALYSIS OF 1990-2003 INCIDENCE TIME TRENDS OF CHILDHOOD DIABETES IN ITALY: THE RIDI STUDY

  1. RIDI Study Group
  1. 1Dept. of Internal Medicine, University of Turin, Italy
  2. 2Cancer Epidemiology Unit, CeRMS and CPO Piemonte, University of Turin, Italy
  3. 3Dept. of Internal Medicine, University of Perugia, Italy
  4. 4Dept. of Pediatrics, Polytechnic University of Marche, Ancona, Italy
  5. 5Dept. of Pediatrics, University of Modena, Italy
  6. 6Dept. of Epidemiology, University of L'Aquila, Italy
  7. 7Dept. of Pediatrics, University of Genova, Italy
  8. 8Unit of Observational Epidemiology, Trento, Italy
  9. 9Università Campus Bio_Medico, University of Rome, Italy
  10. 10Dept. of Pediatrics, University of Napoli, Italy
  11. 11S. Michele Hospital, Cagliari, Italy
  12. 12Dept. of Preventive Medicine, University of Pavia, Italy
  13. 13Dept. Of Pediatrics, University of Florence, Italy
  14. 14Dept. of Epidemiology, Biostatistics and Medical Information Technology, Polytechnic University of Marche, Ancona, Italy

Abstract

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.

Footnotes

    • Received January 31, 2010.
    • Accepted June 10, 2010.

    This Article

    1. Diabetes
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