Residential mobility and the risk of childhood leukemia.

Purpose: An infective origin of childhood leukemia has been postulated, with leukemia developing as a rare response to an infection. Population mixing can result in increased contacts between infected and susceptible individuals and may increase the risk of leukemia. The objective of this study was to investigate the association between residential mobility as an indicator of population mixing at individual level and the risk of leukemia in children (<15 years).

Methods: We conducted a population-based case-control study using Finnish register data. Cases (n = 1,093) were all children diagnosed with leukemia (M9800-M9948 in ICD-O-3) at <15 years of age in Finland in 1990-2011. We chose randomly three controls per case (n = 3,279), free of cancer and alive in the end of the index year (diagnosis of the case). Controls were matched by sex and age. A comprehensive history of residential mobility was constructed from the population registry including overall migration, moving to a larger municipality (more inhabitants), and moving to a municipality with low, intermediate, or high migration intensity. The association between residential mobility and the risk of childhood leukemia was evaluated using conditional logistic regression.

Results: We did not observe consistently increased or decreased risks of childhood leukemia associated with different migration patterns. Overall, residential mobility showed odds ratios nonsignificantly below unity, and no elevated risks were found.

Conclusion: Our results do not indicate that higher residential mobility or moving to municipalities with more inhabitants is associated with risk of childhood leukemia.