Impact of Smokeless Tobacco on Semen Quality: A Systematic Review and Meta-Analysis

Smokeless tobacco products are widely regarded as a safer alternative to smoking. However, a growing body of evidence points to harmful effects on male reproductive health. The aim of this systematic review and meta-analysis was to assess the association between smokeless tobacco use and the principal indicators of male infertility.

This review was conducted in accordance with PRISMA 2020 guidelines and registered with PROSPERO (CRD420251056391). A systematic search of PubMed, Medline, Web of Science, and Google Scholar was performed from January 1993 to December 2025. Observational and interventional studies that examined smokeless tobacco exposure in adult men were eligible. Risk of bias was assessed with ROBINS-I and the certainty of evidence with GRADE.

Sixteen studies with a total of 3401 participants met the inclusion criteria. Smokeless tobacco use was associated with lower sperm motility (mean difference, MD: -9.56; 95% confidence interval, CI: -14.85 to -4.28), lower sperm concentration (MD: -14.90; 95% CI: -21.43 to -8.37), lower sperm vitality (MD: -12.86; 95% CI: -19.86 to -5.86), and a higher proportion of abnormally shaped sperm (MD: +3.58; 95% CI: 0.34 to 6.82). Semen pH was slightly but significantly lower in users (MD: -0.03; 95% CI: -0.04 to -0.02). Semen volume was also lower, but the difference did not reach statistical significance (MD: -0.36; 95% CI: -0.76 to 0.04; p = 0.078). Heterogeneity was high for several outcomes (I² > 90%), but sensitivity analyses did not change the direction of effect. The GRADE certainty of evidence was moderate for all pooled outcomes except semen volume, for which it was low.

Smokeless tobacco use was associated with poorer semen quality, particularly in sperm motility, concentration, vitality, and morphology. These findings are consistent with smokeless tobacco being an important and frequently overlooked risk factor for male infertility, although the evidence is observational and derived largely from South Asian populations. Clinicians should consider asking about smokeless tobacco use during infertility evaluations, and targeted public health measures appear warranted to address its reproductive effects.