Use of a density equalizing map projection in analysing childhood cancer in four California counties

In this study, 401 cases of childhood cancer in four California counties in 1980–1988 were analysed with the innovative methodology of density equalizing map projections. The data were originally collected and analysed by the California State Department of Health Services (DHS). In addition to the n...

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Bibliographic Details
Published in:Statistics in medicine 2001-05, Vol.20 (9-10), p.1499-1513
Main Author: Merrill, Deane W.
Format: Article
Language:English
Subjects:
Adolescent
Biological and medical sciences
California - epidemiology
Child
Child, Preschool
Cluster Analysis
Female
General aspects
Humans
Infant
Infant, Newborn
Leukemia - epidemiology
Male
Maps as Topic
Medical sciences
Neoplasms - epidemiology
Population Density
Tumors
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Summary:In this study, 401 cases of childhood cancer in four California counties in 1980–1988 were analysed with the innovative methodology of density equalizing map projections. The data were originally collected and analysed by the California State Department of Health Services (DHS). In addition to the new analytic technique, the present analysis used population data more detailed and more accurate than those in the DHS analysis. The geographic boundaries of the 259 census tracts in the study area were adjusted according to population at risk so as to make population density everywhere constant; then the 401 case locations were plotted on the density equalized map. If risk is everywhere equal, the resulting distribution of cases should be uniform except for statistical variation. The metric used was a measure of the variability of the density of cases on the density equalized map. The same metric was calculated for independent samples of artificial cases, generated under the null hypothesis of equal risk. The slight geographic non‐uniformity observed among the real cases is well within the limits of variation observed in the samples of artificial cases. In agreement with results published by DHS, we conclude that there is no evidence for geographic variation of risk among the cases studied. Subsets of the data, selected by age, sex, race, time period and cancer site, yielded similar negative results. Copyright © 2001 John Wiley & Sons, Ltd.
ISSN:0277-6715
1097-0258
DOI:10.1002/sim.686