Higher sperm counts in Southern Sweden compared with Denmark

Area of Science:

• Reproductive Endocrinology
• Environmental Health
• Andrology

Background:

• Male reproductive function declines with time, evidenced by decreased sperm concentration and increased testicular cancer incidence.
• Geographical variations in testicular cancer incidence and sperm counts exist, with Denmark showing high rates and Finland showing lower rates.
• Sweden has a 50% lower incidence of testicular cancer than Denmark, suggesting potential environmental or genetic influences.

Purpose of the Study:

• To compare semen parameters between military conscripts from Southern Sweden and Denmark, two genetically similar populations.
• To investigate potential environmental or lifestyle factors affecting male reproductive health in geographically proximate populations.

Main Methods:

• A cohort of 305 Swedish military conscripts was recruited.
• Participants underwent identical investigations as a previously studied Danish cohort, including questionnaires, physical examinations, and semen analysis.

Main Results:

• Swedish men demonstrated a 23% higher mean sperm concentration compared to Danish men.
• Mean total sperm count was 31% higher in Swedish men.
• Seminal volume was 14% higher in the Swedish cohort.

Conclusions:

• Significant differences in reproductive parameters were observed between genetically similar Swedish and Danish populations.
• These disparities could not be attributed to known confounders.
• Unknown environmental or lifestyle-related factors are likely responsible for the observed differences in male reproductive health.