Incidence of type 1 diabetes mellitus in Navarre stabilized in the last eight years

Incidence of type 1 diabetes mellitus raises a number of controversies. Our study aim was to contribute to answer the following questions: Is incidence of T1DM increasing? Is age at onset of type 1 diabetes mellitus decreasing? Which are the sex differences? Which are the characteristics in adults?

A cross-sectional descriptive study using data from a primary source and 3 secondary sources from Navarre collected between 01/01/2009 and 12/31/2016. Annual incidence rates and incidence rate expressed as 100,000 person-years were estimated in the study period by age and sex group. The comparison of the sex and age incidence was made estimating the incidence rate using Poisson's regression methods. The completeness of the register was 96.08%.

During the 8 years analyzed, 428 new cases of type 1 diabetes mellitus were reported (incidence: 8.4/100,000 person-years, 95% CI: 7.6-9.2). Incidence has remained stable and is higher in the group under 15 years old (21.5) than in adults (5.9). Males aged 10-14 years and females aged 5-9 years were the groups with the highest incidence. Incidence then decreased with increasing age. Type 1 diabetes mellitus predominates in males aged 10-45 years, and no changes were seen in age at onset when analized by four-year periods.

Navarre shows a very high incidence of type 1 diabetes mellitus in childhood and a low incidence in adulthood. Peak incidence is seen earlier in girls, but the disease predominates in males. Neither incidence nor age at onset have changed.