Semen quality of young men in Switzerland: a nationwide cross-sectional population-based study

Abstract

Background: Sperm counts have been steadily decreasing over the past five decades with regional differences in the Western world. The reasons behind these trends are complex, but numerous insights indicate that environmental and lifestyle factors are important players.

Objective: To evaluate semen quality and male reproductive health in Switzerland.

Materials and methods: A nationwide cross-sectional study was conducted on 2523 young men coming from all regions of Switzerland, recruited during military conscription. Semen volume, sperm concentration, motility, and morphology were analyzed. Anatomy of the genital area and testicular volume was recorded. Testicular cancer incidence rates in the general population were retrieved from Swiss regional registries.

Results: Median sperm concentration adjusted for period of sexual abstinence was 48 million/mL. Comparing with the 5th percentile of the WHO reference values for fertile men, 17% of men had sperm concentration below 15 million/mL, 25% had less than 40% motile spermatozoa, and 43% had less than 4% normal forms. Disparities in semen quality among geographic regions, urbanization rates, and linguistic areas were limited. A larger proportion of men with poor semen quality had been exposed in utero to maternal smoking. Furthermore, testicular cancer incidence rates in the Swiss general population increased significantly between 1980 and 2014.

Discussion: For the first time, a systematic sampling among young men has confirmed that semen quality is affected on a national level. The median sperm concentration measured is among the lowest observed in Europe. No specific geographical differences could be identified. Further studies are needed to determine to what extent the fertility of Swiss men is compromised and to evaluate the impact of environmental and lifestyle factors.

Conclusion: A significant proportion of Swiss young men display suboptimal semen quality with only 38% having sperm concentration, motility, and morphology values that met WHO semen reference criteria.

Keywords: geographic variations; lifestyle factors; semen quality; sperm count; testicular cancer; young men.

Figure 1

Frequency distribution of basic semen parameters of Swiss men. (A) 17% of cases have oligozoospermia with sperm concentration below 15 Mio/mL, (B) 17% have less than 39 million spermatozoa in their ejaculate, (C) 25% have asthenozoospermia with less than 40% motile spermatozoa, and (D) 43% have teratozoospermia with less than 4% morphologically normal spermatozoa. (E) Pie chart illustrating the number of men with a combination of parameters below WHO reference values; 62% of men has at least one value below the thresholds set for fertile men. Gray columns indicate the percentage of men with values below the WHO thresholds (A–C: n = 2523; D, E: n = 2319).

Figure 2

Minor geographic variations in semen quality in Switzerland. (A) Stratification of men according to their place of living in the three main geographical regions revealed that there are only slight variations in the proportion of men with sperm concentration <15 Mio/mL (Jura, Plateau, Alps). (B) Attribution to each man to an urbanization category shows that there are no differences between the three sperm concentration groups. (C) Stratification according to the linguistic regions as a proxy for lifestyle factors also indicates no variation in sperm counts in the German‐speaking and French‐Italian‐speaking regions. p‐value for comparison of results between sperm concentration categories was calculated using chi‐square test (significant when p <0.05).

Figure 3

Temporal trend of testicular cancer incidence in Switzerland between 1980 and 2014. Gray dots and caps indicate the observed incidence rates with 95% confidence intervals, whereas the black line represents the modeled linear incidence trend. Over the 35‐year period, incidence rates increase of 1.4% every two years (95% CI: 0.7–2.0; p < 0.001).