Parental and infant characteristics and childhood leukemia in Minnesota

Background: Leukemia is the most common childhood cancer. With the exception of Down syndrome, prenatal radiation exposure, and higher birth weight, particularly for acute lymphoid leukemia (ALL), few risk factors have been firmly established. Translocations present in neonatal blood spots and the young age peak of diagnosis suggest that early-life factors are involved in childhood leukemia etiology. Methods: We investigated the association between birth characteristics and childhood leukemia through linkage of the Minnesota birth and cancer registries using a case-cohort study design. Cases included 560 children with ALL and 87 with acute myeloid leukemia (AML) diagnoses from 28 days to 14 years. The comparison group was comprised of 8,750 individuals selected through random sampling of the birth cohort from 1976-2004. Cox proportional hazards regression specific for case-cohort studies was used to compute hazard ratios (HR) and 95% confidence intervals (CIs). Results: Male sex (HR = 1.41, 95% CI 1.16-1.70), white race (HR = 2.32, 95% CI 1.13-4.76), and maternal birth interval >= 3 years (HR = 1.31, 95% CI 1.01-1.70) increased ALL risk, while maternal age increased AML risk (HR = 1.21/5 year age increase, 95% CI 1.0-1.47). Higher birth weights (>3798 grams) (HRALL = 1.46, 1.08-1.98; HRAML = 1.97, 95% CI 1.07-3.65), and one minute Apgar scores <= 7 (HRALL = 1.30, 95% CI 1.05-1.61; HRAML = 1.62, 95% CI 1.01-2.60) increased risk for both types of leukemia. Sex was not a significant modifier of the association between ALL and other covariates, with the exception of maternal education. Conclusion: We confirmed known risk factors for ALL: male sex, high birth weight, and white race. We have also provided data that supports an increased risk for AML following higher birth weights, and demonstrated an association with low Apgar scores.