Objective: To evaluate childhood cancer in relation to duration of breast-feeding.
Setting: Sweden. Records from Child Healthcare Centres were scrutinised regarding information on breast-feeding and other health-related items.
Subjects: All children aged 0-14 y 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 > or = 1 month increased the risk for non-Hodgkin's lymphoma (NHL) 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 > 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.