Time-space clustering among cases of acute leukemia in two Georgia counties.

Statistical analyses were made of the time-space configuration of 406 acute leukemia cases in DeKalb and Fulton Counties, Georgia, over the 13-yr period 1956-1968. Separate analyses were performed for each of three age groups, 0-14 yr, 15-49 yr, and 50 yrplus, cases being assigned to 2and 3-yr time segments and to census tract units according to date of onset and place of residence at diagnosis. Pearson chi-square statistics and Haldane’s moments were used as a measure of homogeneity in case configurations. All calculations took into account agespecific populations for each census tract unit corrected for shifting population density. Evidence of inhomogeneity of time-space configurations, based on case clustering, was found among cases in the 0-14 age group but not at older ages. Clustering was present in both counties whether examined separately or combined, and it was more clearly seen in case distributions in DeKaIb County. Analyses done for various periods of time showed that degree of clustering depended greatly on placement of time boundaries.