Ethnic Difference in Daycare Attendance, Early Infections, and Risk of Childhood Acute Lymphoblastic Leukemia

Abstract

A role for infectious agents has been proposed in the etiology of childhood acute lymphoblastic leukemia (ALL), particularly for common ALL (c-ALL; ALL diagnosed in children ages 2-5 years and expressing CD10 and CD19 surface antigens). We evaluated the possible etiologic role of daycare attendance (a proxy measure for exposure to infectious agents) and infections during infancy in the Northern California Childhood Leukemia Study. A total of 294 incident ALL cases (ages 1-14 years) and 376 individually matched controls were included in this analysis. In non-Hispanic White children, daycare attendance measured by child-hours was associated with a significantly reduced risk of ALL. Compared with children who did not attend any daycare, the odds ratio (OR) for those who had >5,000 child-hours during infancy was 0.42 [95% confidence interval (95% CI), 0.18-0.99] for ALL and 0.33 (95% CI, 0.11-1.01) for c-ALL. Test for trend is also significant, which supports a dose-response relationship. The magnitude of effect associated with the same number of child-hours was stronger for daycare attendance during infancy than for daycare attendance before diagnosis. In addition, self-reported ear infection during infancy was associated with a significantly reduced risk of c-ALL (OR, 0.32; 95% CI, 0.14-0.74) in non-Hispanic White children. In Hispanic children, no association was observed among daycare attendance, early infections, and risk of childhood ALL or c-ALL. These results offer indirect yet strong support for the infectious disease hypothesis in the etiology of ALL in non-Hispanic White children and highlight an important ethnic difference.( Cancer Epidemiol Biomarkers Prev 2005;14(8):1928 -34)

Infections in early life and childhood leukaemia risk: a UK case–control study of general practitioner records

“…Other recent studies have ascertained infections primarily from parental recall. The majority of these studies have observed slight inverse associations between infections or specific types of infections in early life and leukaemia risk (Neglia et al, 2000;Perrillat et al, 2002;Jourdan-Da Silva et al, 2004;Ma et al, 2005), but some studies have demonstrated little evidence of an association (Schuz et al, 1999;Macarthur et al, 2008), whereas others have shown an increased risk of leukaemia after infection (Dockerty et al, 1999;Chan et al, 2002). However, parental recall of infections is open to disease-dependent recall bias and has been shown to be an unreliable measure of both the timing and occurrence of infections (McKinney et al, 1991).…”

“…In support of this theory, various studies have demonstrated associations with various proxy measures of exposure to infection, such as day care attendance (Perrillat et al, 2002;Jourdan-Da Silva et al, 2004;Ma et al, 2005) and breastfeeding (UK Childhood Cancer Study Investigators, 2001). However, only one study has previously reported on ALL in relation to routinely recorded infections in early life .…”

“…However, only one study has previously reported on ALL in relation to routinely recorded infections in early life . Other investigations of leukaemia and infections in early life (Dockerty et al, 1999;Chan et al, 2002;Perrillat et al, 2002;Jourdan-Da Silva et al, 2004;Ma et al, 2005;Macarthur et al, 2008) have primarily ascertained infection from parental recall, but this has been reported to be an inaccurate method for collecting data on childhood infections (McKinney et al, 1991). Furthermore, the parental recall of infections is open to disease-dependent bias as demonstrated by a recent study, which observed that the degree of underreporting of infections that were recorded in GP records differed in parents of children with leukaemia compared to parents of healthy children .…”

Parental social contact in the work place and the risk of childhood acute lymphoblastic leukaemia

“…Since adjusting for parental educational level did not change risk estimates by more than 10%, these two variables were not included in the final statistical models. Although different associations were previously reported between daycare attendance and childhood leukaemia for Hispanic and non-Hispanic white children (Ma et al, 2005), statistical testing for interaction between Hispanic status and parental contact months indicated that the association with childhood ALL (P ¼ 0.81) or c-ALL (P ¼ 0.47) did not differ by Hispanic status; subjects of all race/ethnicity were therefore combined for these analyses.…”

“…Studies have examined the association between childhood leukaemia and different proxy measures of child's risk of infection, including the daycare attendance (Ma et al, 2005) and birth order (Greaves, 2001). Seven childhood leukaemia studies have examined paternal occupational social contact as another proxy measure of child's risk of infection and the results have been inconsistent (Roman et al, 1994;Kinlen, 1997;Fear et al, 1999Fear et al, , 2005Kinlen and Bramald, 2001;Kinlen et al, 2002;Pearce et al, 2004).…”