Sperm quality parameters of Swiss army recruits pre- and peri-COVID-19: a cross-sectional, comparative analysis.

Background: This study evaluates sperm quality among young Swiss military recruits in 2021 and compares the findings with data collected between 2005 and 2017, in the context of the reported global decline in sperm quality. Methods: This cross-sectional study compares two cohorts of Swiss men aged 18 to 30 years. Group 1 (Rahban) included 2523 participants examined between 2005 and 2017, and Group 2 (LoCoMo) comprised 194 recruits assessed in 2021. Semen analyses were performed according to WHO guidelines. In Group 2, reproductive hormones (FSH, LH, testosterone) were additionally measured. Comparisons between cohorts were conducted, and geographic variation within Group 2 was assessed by language region and settlement type. Results: Based on WHO reference criteria, 17% of soldiers of Group 2 (LoCoMo in the peri-COVID period) had oligozoospermia, 35% had asthenozoospermia, and 14% teratozoospermia. Compared to Group 1 (Rahban), sperm concentration, total sperm count, progressive sperm motility and sperm morphology remained similar. Evidence for differences in LH and FSH levels of Group 2 were found in three different sperm concentration groups, while no evidence of differences were shown in testosterone levels. No evidence of differences in distribution of sperm concentration groups were found between language regions (Latin vs. Non-Latin) and settlement types ((Sub)urban vs. Rural). Conclusions: Sperm quality remained stable in 2021 apart from those with recent COVID-19 infections compared to the period from 2005 to 2017. Larger studies are required to explore spatial correlation of sperm parameters and other influencing factors.