A study of the geographical pattern of cancer mortality for selected sites by means of factor analysis

Abstract

The spatial distribution of cancer mortality and morbidity has been studied by many authors, and its characteristic pattern as to the various cancer sites was the object of the research of many epidemiologists.

It has been generally recognized that any of the specific factors do not contribute independently but interdependently to the etiology in chronic diseases. With this in mind, it is natural to assume that there exist multiple factors which collaborate with each other in the pathogenesis of cancer of various sites.

To test interdependence of variables, we set out to analyse the pattern of the geographical distributions of the cancer deaths in Japan, using the method of factor analysis which has been characterized as a useful method for analyzing the correlated variables.

Five independent factors are extracted from the mutual correlations among the site-specific mortality rates on various cancers and that these factors were commonly found in both sexes, although slight discordance was noticed in some factors. Among the factors extracted, the first one attracted us the most, since the fact that bone, bladder, skin and buccal cancers clustered in one group suggest a possible relationship of these cancers to atmospheric temperature. An alternative fact that interests us is the conspicuous variability in the geographical distribution of lung cancer. Finally, we add that consistently high correlations were obtained for the mortality rates between any two of the different three time periods.