Socioeconomic Status and Childhood Leukaemia

Abstract

P-398 Introduction: Some epidemiological studies have found a relationship between socio-economic status (SES) and some childhood cancers, such as lymphoma or leukaemia. In the present study an attempt was made to assess socio-economical class in a case-control study investigating childhood leukaemia risk factors, by using a deprivation index calculated at a municipality level. Methods: Leukaemia cases (age <15) were from a population cancer registry over an incidence period of twenty years (1978–1997); four controls per case, matched by gender and date of birth, were randomly sampled from population files. For each subject exposure to power lines electromagnetic field and to traffic road air pollution were estimated. A deprivation index was also assigned to each child according to its municipality of residence. This index is built by considering 5 socio-economic indicators: low education, unemployment, rented occupier housing, lone parents with children, no indoor bathroom. Conditional logistic regression was performed to estimate relative risks (RR) for categories of increasing deprivation level. Results: Two-hundred and eighty-five (285) subjects (60 cases and 225 controls) were classified in the reference category (low deprivation level), 159 (33 cases and 126 controls) in the middle group, while 156 subjects (27 cases and 129 controls) were considered as highly deprived. A protection effect for leukaemia appeared for increasing deprivation level, though not statistically significant: a RR of 0.98 (95% confidence interval [CI] = 0.61–1.59) for the middle group and a RR of 0.78 (95% CI = 0.47–1.29) for the more deprived group, both compared to the reference category. Furthermore, no confounding effect for environmental factors investigated in this same case-control study (electromagnetic fields or traffic air pollution) was found analysing correlations between deprivation index and both environmental exposures. Conclusions: Even though the index used was probably too rough (children residing in the same municipality were classified in the same category), a possible confirmation of the association between SES and childhood leukaemia is found. Moreover, the results obtained with the same study group for electromagnetic fields exposure or traffic exposure as risk factors for leukaemia, seem not to be confounded by SES.