Higher sperm counts in Southern Sweden compared with Denmark

Abstract

Background: A common aetiology behind time-related deterioration of male reproductive function, including decline of sperm concentration and rising incidence of testicular cancer and cryptorchidism, has been suggested. Accordingly, a high incidence of testicular cancer and low sperm counts have been observed in Denmark, while in Finland opposite figures were found. This may be due to genetic factors. The incidence of testicular cancer is 50% lower in Sweden than in Denmark. Data on sperm counts in a population of Danish military conscripts have been published and we wished therefore to compare them with semen parameters in a corresponding cohort from Southern Sweden, geographically and genetically very closely related to Denmark. Methods: A total of 305 military conscripts was recruited and investigated in an identical way as those in the Danish study including a questionnaire, physical examination and semen analysis. Results: Men born and raised in Sweden had a 23% higher mean sperm concentration, a 31% higher mean total sperm count and a 14% higher seminal volume compared with their Danish counterparts. Conclusions: The differences in reproductive parameters between the two genetically very similar populations could not be explained by possible confounders and may be due to unknown environmental or lifestyle-related factors.