Early child-care and preschool experiences and the risk of childhood acutelymphoblastic leukemia

An infectious etiology for childhood acute lymphoblastic leukemia (ALL) has been suggested, yet few studies have focused on the role of early child ca re. Day-care histories were examined in a case-control study of ALL in New York State. Cases (n = 255) were diagnosed at one of four referral centers between 1980 and 1991; controls (n = 760) were randomly selected from liveb irths in the 31 counties served by the referral centers. Self-administered questionnaires were mailed to the parents of cases and controls in 1995. Da y-care histories were censored at the age of diagnosis for cases and at an equivalent date for controls. The odds ratio for children who stayed at hom e compared with those who attended day care for >36 months was 1.32 (95% co nfidence interval (CI): 0.70, 2.52); the odds ratios for 1-18 and 19-36 mon ths of day care were 1.74 (95% CI: 0.89, 3.42) and 1.32 (95% CI: 0.64, 2.71 ), respectively. Elimination of cases with T-cell ALL enhanced the risk, St arting care at an earlier age was not associated with a decreased risk of A LL. These findings do not support the hypothesis that infrequent contact wi th peers during early childhood could delay exposure to infectious diseases and increase the risk of ALL.