Spatial and space-time clustering of childhood acute leukaemia in France from 1990 to 2000:: a nationwide study

This study aimed to investigate the spatial and space-time distributions of cases of childhood acute leukaemia ( CL) during 1990 2000 over the whole French territory. A global spatial heterogeneity and a spatial autocorrelation were first considered using the methods proposed by Potthoff and Whittinghill, Moran and Rogerson methods. The presence of space-time interaction between the places of residence and the dates of diagnosis was investigated with the Knox's test. Finally, the Kulldorff's statistic permitted to scan the whole territory in search for localised clusters. Two time periods were considered ( 1990 - 1994, 1995 - 2000). Overall, a statistically significant spatial heterogeneity of a very small magnitude was observed in the incidence of CL over 1990 - 1994, but neither over 1995 - 2000 nor over the whole time period. Moreover, a significant overdispersion of 5.5% was evidenced for 0 - 4 year children living in isolated areas with more than 50 inhabitants per km(2). Cases older than 10 years living in the same area at diagnosis also tended to cluster within 6 months.