Markers of infection, breast-feeding and childhood acute lymphoblastic leukaemia

Infections are suspected to play a role in the aetiology of childhood leuka emia. In 1989-95, we evaluated the relation between childhood acute lymphob lastic leukaemia and pre- and postnatal markers of exposure to infection, a s well as breast-feeding. A population-based case-control study was carried out in certain regions of Quebec, Canada, in 1989-95 including 491 inciden t cases diagnosed between 1980 and 1993 and aged between 0 and 9 years. An identical number of healthy controls matched for age, sex and region of res idence at the date of diagnosis was included. Having older siblings, mother 's use of antibiotics during pregnancy, and being born second or later were all associated with increased risk of leukaemia while early day-care atten dance (odds ratio (OR) = 0.49; 95% CI 0.31-0.77), and breast feeding (OR = 0.68; 95% CI 0.49-0.95) were significantly protective. A marker of populati on mixing was not a risk factor. When including all variables defining fami ly structure in a model, having older siblings at time of diagnosis was a r isk factor among children diagnosed before 4 years of age (OR = 4.54; 95% C I 2.27-9.07) whereas having older siblings in the first year of life was pr otective among children diagnosed at 4 years of age or later (OR = 0.46; 95 % CI 0.22-0.97). (C) 2000 Cancer Research Campaign http://www.bjcancer.com.