Introduction and Aim: The Incidence of Type 1 diabetes mellitus (T1DM) varies markedly between populations and over time. Recently a number of high incidence countries, including Ireland, have reported a stabilisation and/or reduction in their T1DM incidence rate (IR) in childhood. Ireland, a high incidence country for T1DM, experienced a dramatic increase in T1DM incidence between 1997 and 2008, a stabilisation in incidence between 2014 and 2018 followed by a minor reduction in incidence in the period 2014 to 2018. This study sought to determine IRs for 2019 to 2021 to clarify if this reduction in IR had continued.
Methods: Using the established mechanism of the Irish Childhood Diabetes National Register (ICDNR), incident cases of T1DM in those aged under 15 years were prospectively recorded in all 19 centres nationally providing care to children and young people with diabetes. Following verification of cases, IRs were calculated. Capture-recapture methodology was employed to provide a measure of ascertainment. Population data derived from census data from the Central Statistics Office was used.
Results: A total of 1,030 cases were reported in the period 2019 to 2021 (age range 0.51 – 14.96 years), with significantly more males (542, 53%) and male to female ratio of 1.11. Standardised IRs for T1DM in the period increased overall, and were: 31.1; 32.4; and 37.8/100,000/year respectively. The incidence increased in both males and females. As in previous years the highest IR was in the 10-14-year-old age category (approximately 50 % of total cases) in 2019 and 2020. However, in 2021 the highest incidence was in the 5-9 year old age category (accounting for 40% of total cases).
Conclusions: The incidence of T1DM in Ireland, a high incidence country has started to rise again. In 2021 the highest incidence has been noted in the 5-9 year old age category for the first time since epidemiological monitoring commenced in this population. This increase in incidence and move to an earlier age at diagnosis may reflect increased environmental pressure, such as viral infection, in this population or the previously recognised periodicity in T1DM incidence. Ongoing epidemiological monitoring of T1DM through national registers is vital to support appropriate healthcare planning, paediatric diabetes management, clinical audit and, research relating to T1DM aetiology.
15 Sep 2022 - 17 Sep 2022