Cyclical and seasonal variations in the incidence of type 1 diabetes mellitus between 1985 and 2016 in Bauru, São Paulo, Brazil

T1DM cyclical variations with a 7.5-year cycle were observed, with girls showing a pronounced variation and a distinct 5-year cycle. Seasonal variations were found among girls, particularly in the 5-9.99-year age group. Outbreaks of H1N1 and dengue, along with the lowest temperatures, coincided with higher incidence rates, aligning with the 7.5-year cycles. Targeted health policies are needed to mitigate the impact of these factors, supporting surveillance, early diagnosis, and preventive strategies for T1DM.