Breast-feeding duration and the risk of malignant diseases in childhood in Sweden

Objective: To evaluate childhood cancer in relation to duration of breast-feeding. Setting: Sweden. Records from Child Healthcare Centres were scrutinised regarding information on breastfeeding and other health-related items. Subjects: All children aged 0-14y with a malignant disease (benign brain tumours included) during the time period 1988-91 (n=962) were identified from the Swedish Cancer Register. An equal number of controls matched for sex and age were selected from the Swedish Birth Register. Results: Information was obtained for 835 cases and 860 controls. Overall, duration of breast-feeding did not influence the risk for a malignant disease in this age group. However, breast-feeding greater than or equal to 1 month increased the risk for non-Hodgkin's lymphoma (NI-IL) yielding an odds ratio (OR) 5.5 with 95% confidence interval (CI) 1.2-25. Breast-feeding 1-<6 months gave OR 5.1, CI 1.1-24 and <greater than or equal to>6 months gave OR 7.0, CI 1.3-37 with a significant trend (P=0.04). Adjustment for maternal and birth-related co-variates gave similar results. For other malignancies no significant changes of the risk were obtained. Conclusions: Overall, no association between duration of breast-feeding and childhood malignancies was found except for a significantly increased risk for NHL, but this was based on low numbers of cases and needs to be confirmed in other investigations.