Childhood acute leukemia and type 1 diabetes in children: A nationwide case-control study.

Etiology of childhood acute leukemia is largely unknown, though environmental factors and infection-related immune responses may contribute. Type 1 diabetes mellitus (T1DM), an autoimmune disease also with onset primarily in childhood, shares risk factors with leukemia, including childhood infection patterns. Epidemiological evidence suggests a link between T1DM and leukemia, but the extent of this association remains unclear. We identified 1626 leukemia cases diagnosed under 18 years of age (1990-2019) from the Finnish Cancer Registry, with three age- and sex-matched controls per case. Participants with Down syndrome or pancreatitis were excluded. Conditional logistic regression, adjusted for maternal smoking and large for gestational age, was used in the data analysis. Patients with T1DM, regardless of whether they were diagnosed before or after leukemia, demonstrated increased risk of acute leukemia, with an odds ratio (OR) of 2.0 (95% CI 1.1-3.5). The association was attenuated after adjustments (OR = 1.7, 95% CI 0.9-3.0). In the univariate analysis, a clear association was observed for acute lymphoblastic leukemia (ALL) (OR = 1.9, 95% CI 1.04-3.4) and an imprecise association of similar magnitude for acute myeloid leukemia (AML). For ALL diagnosed at ages 10-17 years, an OR of 5.4 (95% CI 1.8-16.1) was observed. The order of disease onset did not significantly impact the association. Our findings show an association between T1DM and acute leukemia, particularly ALL in older children, and treatment-related pancreatitis does not fully explain this co-occurrence. Further investigation is warranted to explore potential common etiological factors, such as infectious diseases.