Rates of childhood cancer are often reported to be lower in low-income countries, a pattern that has long been attributed to underdiagnosis or incomplete cancer registration. A new study from Uppsala and Stockholm universities in Sweden offers an opportunity to examine that assumption in a setting with universal healthcare and high-quality registry data. Using linked national registers, the researchers followed more than 3 million Swedish-born children and investigated childhood cancer incidence according to migrant background.
Overall, childhood cancer incidence was broadly similar across migrant generations. However, clearer differences emerged when the researchers considered parental country of origin. Children whose parents—particularly mothers—came from low-income countries had lower incidence of leukemia and central nervous system tumors than children with Swedish background. In contrast, lymphoma incidence was somewhat higher in some second-generation groups.
A particularly notable finding was that these patterns did not vary clearly according to how long parents had lived in Sweden before the child’s birth. This weakens a simple explanation based only on time spent in the host environment. Because all children in the study were born and diagnosed within the same healthcare system, the findings also challenge the idea that international differences in childhood cancer are explained solely by underdiagnosis or incomplete registration in lower-resource settings.
Instead, the results suggest that at least part of the global variation in childhood leukemia and central nervous system tumor incidence may reflect real underlying differences, potentially linked to inherited or early-life factors carried across populations. Although the study cannot pinpoint the precise mechanisms, it adds an important piece to the puzzle and highlights how migrant studies can help disentangle the roles of biology, environment, and healthcare access in childhood cancer research.
Citation:
Article Title: Childhood cancer incidence by migrant background in Sweden (1991-2021): a nationwide cohort study
Authors: Genevieve Allen, Elena Extrand, Siddartha Aradhya, Hanna Mogensen, Hannah L Brooke.
Published In: Lancet Reg Health Eur. 2026 Feb 20;64:101621. doi: 10.1016/j.lanepe.2026.101621. PMID: 41767890; PMCID: PMC12936785.