Effects of cigarette smoking on semen quality, reproductive hormone levels, metabolic profile, zinc and sperm DNA fragmentation in men: results from a population-based study.

Plain-language summary

This study set out to examine how cigarette smoking affects semen quality, hormone levels, metabolic health, zinc levels, and sperm DNA damage in young Russian men. It compared 450 smokers (split into moderate and heavy smokers) to 772 non-smokers across different ethnic groups, measuring semen parameters, blood markers, and zinc levels. The study found that heavy smoking was linked to worse semen quality, higher sperm DNA damage, lower zinc levels, and poorer metabolic health, with the strongest effects seen in Slavic men. It concluded that smoking's impact on male fertility may vary by ethnicity, possibly due to differences in antioxidant defenses.

Key findings

• Heavy smoking (>10 cigarettes/day) was linked to lower semen volume, total sperm count, sperm concentration, and motility.
• Heavy smokers had higher sperm DNA fragmentation (breaks in the genetic material inside sperm, more breaks mean a lower chance of conception and live birth, so lower is better) and more abnormally shaped sperm.
• Smokers had lower zinc levels in both blood and semen, and worse metabolic health markers.
• Ethnic differences were seen, with Slavic smokers showing the strongest negative effects on semen quality and zinc levels, while Yakuts had a slight drop in testosterone and rise in triglycerides.
• Smoking showed no relationship with LH, FSH (follicle-stimulating hormone, the pituitary signal that drives sperm production), inhibin B (a hormone made by the testicles that reflects sperm-producing capacity, a low level points to weaker sperm production), testosterone or estradiol.