Peer-reviewed Article
Cancer incidences in Europe related to mortalities, and ethnohistoric, genetic, and geographic distances
Abstract
We have previously shown that geographic differences in cancer mortalities in Europe are related to (in order of importance): geographic distances (reflecting environmental differences), ethnohistoric distances (encompassing cultural and genetic attributes), and genetic distances of the populations in the areas studied. In this study, we analyzed the relations of the same three factors to European incidences of 45 male and 47 female cancers. Differences in cancer incidences are correlated moderately, first with geographic distances, and then with genetic distances, but not at all with ethnohistoric distances. Comparing these findings to the earlier ones for cancer mortalities, we note the reversal in the importance of ethnohistory and genetics, and the generally lower correlations of incidence differences with the three putatively causal distance matrices. A path diagram combining both studies demonstrates the lack of cultural carcinogenic effects, but suggests cultural influences on procedures such as the registration of deaths in different political entities. Additionally, the relatively large correlation between ethnohistoric distances and mortality differences is caused by common factors behind the correlation of ethnohistoric and geographic distances. Geographic proximity results in similar ethnohistories. The direct effects of genetic distances are negligible and only their common effects with geographic distances play a role, accounting for the weak to negligible influence of genetics on incidence and mortality differences. Apparently, the genetic systems available to us do not substantially affect cancer incidence or mortality. We present indirect evidence that international differences in the quality of cancer rate data are greater in mortalities than in incidences.
In an earlier study (1), we showed that differences in cancer mortalities of local populations in Europe are correlated more with their ethnohistoric distances than their genetic distances. We chose to study cancer mortalities before incidences because they were available in cancer atlases yielding balanced data matrices. The present study on cancer incidences required compilation of data from several volumes (2–5) in which the number of population samples and cancers recorded varied, resulting in unbalanced data matrices. Here we analyze cancer incidence rates as we had earlier analyzed mortalities and compare our incidence findings to those for mortality.
Differences in cancer rates between populations are affected in part by their geographic distances and ethnic differences (6, 7). Epidemiologists ascribe differences in cancer rates to genetic and environmental factors. Although some of the loci used in this study have been associated with cancer (7, 8), the majority of the genetic factors we used provides only an estimate of overall genetic distances between populations. Environmental factors known to affect cancer rates include cultural factors such as dietary habits, sexual practices, occupational practices, etc. Some other environmental components representing the physical environment are present in the geographic distances we used. Still others, such as pollution, are not well described by our covariates. The ethnohistoric differences estimated in our study comprise both genetic and cultural components. We attempt to disentangle the effects of these factors by means of partial matrix correlations as detailed below.
Full Citation
Sokal, R.R., N.L. Oden, M.S. Rosenberg, and B.A. Thomson (2000) Cancer incidences in Europe related to mortalities, and ethnohistoric, genetic, and geographic distances. Proceedings of the National Academy of Sciences USA 97(11):6067–6072.
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PMID: 10823950
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