Genetic and environmental factors affect the onset of type 1 diabetes mellitus

Background: Type 1 diabetes mellitus (T1DM) is influenced by genetic as well as environmental factors. Its incidence has risen considerably since the 1950s. Objective: This study investigates T1DM time trends from 1989 to 2008 and tries to establish whether breast/bottle feeding, a family history of diabetes, and childhood infectious diseases influence age at onset. Methods: The study used the population-based registry of childhood diabetes of Abruzzo (central Italy), which includes incident cases of patients aged less than 15 yr. The pooled 1989-2008 global ascertainment of the registry was 95%. The trend was estimated using age-period-cohort models Results: Overall standardized incidence rates (SIR) increased by 73.38% from 8.94 (1989-1993) to 15.50 (2004-2008). A rising trend was found in all age groups; annual rises were significant for the overall population (3.40%, p < 0.01) and for 5-9 yr olds (5.48%, p < 0.01). SIR increased in males by 106.26%, from 9.26 in 1989-1993 to 19.10 in 2004-2008. Early T1DM onset was related to mixed feeding (6.80 yr +/- 3.58 vs 8.20 +/- 3.81 yr; p = 0.002), and a family history of T1DM (6.71 +/- 3.96 yr vs. 8.09 +/- 3.77 yr; p = 0.014), whereas multiple infections delayed age at onset (9.71 +/- 2.37 yr vs 7.71 +/- 2.82 yr; p = 0.03). Conclusions: T1DM incidence exhibits a rising time trend that is particularly evident in males and in middle age group; mixed feeding and a family history of diabetes are associated with early onset, multiple bacterial infections contracted before diabetes are associated with a significant delay.