Divergent long-term trends in semen quality and reproductive hormones across the COVID-19 pandemic era in infertile men: an age-stratified retrospective study

Male reproductive dysfunction has been reported during the acute phase of COVID-19. However, the long-term patterns in semen quality and hormonal parameters across the extended pandemic and post-pandemic periods, and whether these patterns differ by age, remain poorly characterized. This large-scale, retrospective study was conducted to delineate these trajectories in infertile men. Among 90,125 records, normal sperm morphology showed a sustained deficit: the proportion of men with morphology ≥ 4% declined from 88.9% pre-pandemic to 55.1% in Post-Phase 2 (p < 0.001), with nearly half falling below the WHO clinical threshold (4%). Serum testosterone decreased modestly from 4.46 to 4.19 ng/mL (6.1% reduction; (p = 0.006) but remained above the hypogonadism threshold for most men. These alterations persisted two years into the post-pandemic period without returning to pre-pandemic baselines. The COVID-19 pandemic was associated with persistent, clinically meaningful deficits in normal sperm morphology and a moderate, non-hypogonadal testosterone suppression, with distinct age-dependent patterns. These findings underscore the need for age-stratified reproductive health surveillance following major population-level stressors.