Childhood leukemia and infectious diseases in the first year of life: a register-based case-control study.

In the Netherlands, a nationwide register of children with leukemia formed the basis for a case-control study (1973-1980). Population controls were matched with the cases for the year of birth, sex, and place of residence at the time of diagnosis. The information was collected by mailed questionnaires addressed to the parents. The analyses concerned infectious diseases in the first year of life of children with acute lymphocytic leukemia and their controls. Common colds, periods of fever, and primary childhood infections showed relative risks (RR) of 0.8, 0.9, and 0.8, respectively, after adjustment for birth order, family size, social class, and residential space. Furthermore, fewer cases reported infectious diseases which required hospitalization in their first year of life (RR = 0.6, 95% confidence interval (CI) = 0.4-1.0). The general infection risk profile of children with acute lymphocytic leukemia is compatible with these findings: there were more first-born children among the patients (RR = 1.8; 95% CI = 1.1-2.7), more children from one-child families (RR = 1.4; 95% CI = 0.8-2.3), more children of parents with higher education (RR = 1.2; 95% CI = 0.9-1.5), and more rooms in patient's houses (RR = 1.4; 95% CI = 0.6-2.6).