Increasing incidence of type 1 diabetes between 1986 and 2015 in Bauru, Brazil.

Aims: To assess temporal trends in the incidence of type 1 diabetes in Bauru, São Paulo State, Brazil from 1986 to 2015.
Research Design and Methods: The yearly incidence of type 1 diabetes (per 100,000/yr) from 1986 to 2015 was determined in children ≤14yr of age, using individual case notification and the capture and recapture method.
Results: During thirty years (1986-2015), 302 cases were diagnosed in our population. The overall incidence was of 12.8/100,000 (95% CI: 11.2-14.4), ranging from 2.8/100,000 in 1987 to 25.6/100,000 in 2013 with a 9.1-fold variation. It was non-significantly higher in girls [13.7 (95% CI: 11.4-16.1)] than in boys [12.0 (95% CI: 9.8-14.2)] (p=0.48) and significantly higher in the 5-9yr [14.6 (95% CI: 11.8-17.4)] and 10-14yr [15.8 (95% CI: 12.7-18.8)] age ranges compared to the 0-4yr [8.1 (95% CI: 6.0-10.2)] age range (p<0.001). The majority of diagnoses were made in colder months. The patterns of incidence were very high and high in 80.0% of the study-years.
Conclusions: The incidence of type1 diabetes in children ≤14yr has increased in Bauru, Brazil, in the last thirty years, in approximately 3.1% annually, with an absolute crude increase of 2.5-fold. These findings pose Brazil as a country with high incidence of type 1 diabetes. All Brazilian regions should be enrolled in future studies to determine the factors that contribute to the predisposition to type 1 diabetes in our population and to the steep rise in its incidence.
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