Population mixing and risk of childhood acute lymphoblastic leukemia.

摘要

The ultimate causes of childhood acute lymphoblastic leukemia (ALL) are unknown. Leo J. Kinlen has hypothesized that population mixing, especially in isolated, rural areas, spreads an unknown virus, leading to increased rates of childhood ALL. This was examined in three studies.; Study 1 was an ecological analysis of data from 24 US cancer registries on children under age 5 across four urbanization strata. In metropolitan areas, ALL incidence was lower among blacks (RR = 0.38) and Asians/Pacific Islanders (RR = 0.78) than whites. Among white children, incidence decreased across four urbanization strata from most urban to most rural, from 67 to 62 to 65 to 54 cases per million person-years at-risk, contrary to Kinlen's classic scenario. The rural-urban gradient was only significant among males.; Study 2 was an ecological analysis of Surveillance, Epidemiology, and End Results Program and US Census data. Incidence among males was associated with proportion moved 1985-1990 (RRs = 1.3, 1.9, and 1.3 for the second, third, and fourth quartiles) and race (RR = 0.5 for blacks). Incidence among females was associated with household income ≥ {dollar}5,000 (RRs = 1.2, 1.0, and 1.5 for the second, third, and fourth quartiles), race (RR = 0.4 for blacks), and urbanization (RRs = 1.1, 0.6, and 0.5 for small metropolitan, adjacent nonmetropolitan, and nonadjacent nonmetropolitan counties versus large metropolitan counties). The results were consistent with a viral etiology.; Study 3 was a case-control analysis of 470 matched pairs in nine states from 1989-1993. Perinatal relocation was directly associated with ALL under age 5 (OR per move = 1.35), and, analyzed dichotomously, interacted with sex (OR = 2.75 for mobile males versus non-mobile males, 1.83 for non-mobile females, and 1.78 for mobile females). Household income {dollar}40,000 was directly associated with ALL (OR = 2.28) before age 5. Children of non-high school graduate mothers had an increased risk of ALL occurring before age 5 (OR = 2.52). These results support the population-mixing hypothesis.; Overall, a viral etiology is supported, but not the Kinlen hypothesis. Further research is warranted.