Women smoking and testicular cancer: one epidemic causing another?

In many countries the incidence of testicular cancer has increased epidemically, but the aetiology remains obscure. Maternal smoking during pregnancy has been suggested to be a cause, but a satisfactorily valid assessment of the hypothesis is still lacking. To evaluate the epidemiological relevance, we assessed the ecological correlation between female smoking habits and testicular cancer incidence in the Nordic countries. Data on smoking prevalence among women in 5-year birth cohorts 1910-1940, at 25-29 years of age, were obtained through past studies of smoking habits in Sweden, Denmark, Norway and Finland. Testicular cancer incidence in the presumed offspring birth cohorts 1938-1968, was calculated using data from the respective cancer registries. For comparison, a similar analysis of male smoking and testicular cancer in the presumed offspring cohorts was carried out. The Pearson correlation coefficient between female smoking prevalence and testicular cancer incidence in the generation of the presumed offspring was 0.9 (p<0.0001) for all countries combined. With the exception of Finland, the country-specific correlations were of the same magnitude. In multivariate analysis, there was no correlation with male smoking. The strong geographical and temporal correlations between female smoking and testicular cancer indicate that if smoking during pregnancy is a cause of testicular cancer in the offspring, part of the increasing trends could be explained, and more importantly: avoided, by primary prevention.