The study investigated the role of factors considered related to the early stimulation of the immune system in the aetiology of childhood lymphoma. The national registry-based case-control study, Escale, was carried out in France over the period 2003-2004. Population controls were frequency matched with the cases on age and gender. Data were obtained from structured telephone questionnaires administered to mothers. Odds ratios (ORs) were estimated using unconditional regression models adjusted for potential confounders. Data from 128 cases of Hodgkin's lymphoma (HL) aged 5-14 years, 164 cases of non-Hodgkin's lymphoma (NHL) aged 2-14 years and 1,312 controls were analyzed. Negative associations were observed between HL and day care attendance [OR = 0.5 (0.2-1.2)] and between HL and repeated early common infections among non-breastfed children [OR = 0.3 (.2-0.7), p = 0.003] [OR for breastfed children: 1.0 (.5-2.1)], but not for the other factors investigated. Negative associations were observed between NHL and birth order 3 or more [OR = 0.7 (0.4-1.1)], prolonged breastfeeding [OR = 0.5 (0.3-1.0)], regular contact with farm animals [OR = 0.5 (0.3-1.0)], frequent farm visits in early life [OR = 0.6 (0.4-1.1)] and history of asthma [OR = 0.6 (0.3-1.1)]. In conclusion, the results partly support the hypothesis that an abnormal maturation of the immune system may play a role in childhood HL or NHL, and call for further investigations.
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