Association of early life factors and acute lymphoblastic leukaemia in childhood: historical cohort study

In a historical cohort study of all singleton live births in Northern Ireland from 1971-86 (n=434933) associations between early life factors and childhood acute lymphoblastic leukaemia were investigated. Multivariable analyses showed a positive association between high paternal age (greater than or equal to 35 years) and acute lymphoblastic leukaemia (relative risk=1.49: 95% confidence interval (CI)=0.96-2.31) but no association with maternal age. High birth weight (greater than or equal to 3500 g) was positively associated with acute lymphoblastic leukaemia (relative risk=1.66; 95% CI=1.18-2.33). Children of mothers with a previous miscarriage or increased gestation (greater than or equal to40 weeks) had reduced risks of ALL (respective relative risks=0.49; 95% CI=0.29-0.80, and 0.67; 95% CI=048-0.94). Children born into more crowded households (greater than or equal to 1 person per room) had substantially lower risks than children born into less crowded homes with also some evidence of a lower risk for children born into homes with three adults (relative risks=0.56; 95% CI=0.35-0.91 and 0,58: 95% CI=0.21-1.61 respectively). These findings indicate that several early life factors, including living conditions in childhood and maternal miscarriage history, influence risk of acute lymphoblastic leukaemia in childhood.