Table 3. External paternal factors and fertility.
| Citation | Study design | Subject | Exposure | Reproductive outcome | OR (95% CI), p-value, overall trend | Key finding | |
|---|---|---|---|---|---|---|---|
| Tang et al (2019) [41] | Cohort | 1,631 males | Smoking | Semen quality, semen volume, oligospermia, sperm motility | p<0.001 | Cigarette smoking (≥10 packs/y) is associated with lower semen volume and total sperm count but increased motility. | |
| p<0.05 | |||||||
| p<0.05 | |||||||
| Rehman et al (2019) [42] | Cross-sectional | 165 infertile vs. 211 fertile males | Smoking | T and SHBG levels, semen quality | p<0.05 | Reduced sexual hormone levels which alters sperm total count and morphology but do not impact their motility. | |
| Gaur et al (2010) [43] | Cohort | 100 cases vs. 100 controls | Smoking | Asthenozoospermia | p<0.0001 | Positive correlation between quantity of cigarettes smoked or amount of alcohol intake and altered sperm parameters but alterations are observed even at low degrees of alcohol/tobacco addiction. | |
| Teratozoospermia | p<0.05 | ||||||
| 100 cases vs. 100 controls | Alcohol | Oligozoospermia | p<0.05 | ||||
| Teratozoospermia | p<0.001 | ||||||
| Borges et al (2018) [44] | Cohort | 965 males | Smoking | Semen quality, fertilization and blastocyst formation rate | p<0.05 | Cigarette smoking and alcohol consumption reduce semen quality, in terms of total sperm count, fertilization rates, and blastocyst formation rates. | |
| Alcohol | DNA fragmentation | p<0.01 | |||||
| Sperm concentration, fertilization and blastocyst formation rate | p<0.05 | ||||||
| Kasman et al (2018) [46] | Cohort | 758 males and 1,076 females | Marijuana | TTP | TR 1.08 (0.79–1.47) | No significant impact of marijuana use on TR. | |
| Wise et al (2017) [47] | Cohort | 1,125 couples | Marijuana use | Fecundability | FRs 0.87 (0.66–1.15) | FRs indicate no association between marijuana use and fecundability. | |
| <1 time/wk | FRs 1.24 (0.90–1.70) | ||||||
| ≥1 time/wk | |||||||
| Nassan et al (2019) [48] | Cohort | 662 sub-fertile males | Marijuana use current/past never | Semen quality, concentration and motility | p<0.001 | After adjusting for potential confounders, marijuana users have significantly higher sperm concentration and motility than never users. | |
| Gundersen et al (2015) [100] | Cohort | 1,215 males | Marijuana | Sperm concentration | 1.07 (0.62–1.87) | After adjustment for confounders, regular marijuana smoking was not associated with lower sperm concentration nor total sperm count. | |
| Sperm total count | 1.14 (0.69–1.89) | ||||||
| Pichini et al (2012) [45] | Cohort | 164 couples and 24 individuals | Cannabinoids and cocaine users vs. non-users | Urinary T | p<0.05 | Male drug consumption was associated with significantly lower urinary T concentrations (mean 105.5±21.1 SD vs. 124.5±46.5 mg/24 h). | |
| Tielemans et al (2000) [51] | Cohort | 726 couples | Organic solvents | IVF implantation rate | OR 0.24 (0.06–0.91) | Couples with male partner exposed to organic solvents have reduced IVF implantation rates. Level of exposure matters. | |
| Pesticides | OR 1.57 (0.33–7.44) | ||||||
| Metal dust and fumes | OR 1.44 (0.57–3.61) | No reduction found after exposure to pesticides, metal dust and fumes or welding fumes. | |||||
| Welding fumes | OR 1.20 (0.31–4.68) | ||||||
| Dodge et al (2015) [52] | Cohort | 218 couples | Methyl paraben | Live birth rate after IUI | aOR 0.19 (0.04–0.82) | Paternal professional exposure to methyl paraben at a specific concentration (10.5~29.0 ng/mL) is associated with decreased odds of live birth following IUI. | |
| Campagna et al (2015) [53] | Cohort | 1,223 couples | DDT | Early fecundity | FR 1.22 (0.84–1.77) | Among the spouses of DDT workers (the antimalaria environmental agent), fecundability did not vary during DDT handling nor in the following decade. | |
| Fecundity 10 years after exposure | FR 1.01 (0.67–1.50) | ||||||
| Buck Louis et al (2016) [50] | Cohort | 501 couples | Heavy metals/non-persistent chemicals | Fecundability and specific exposure | OR 0.83 (0.70–0.98) | Specific exposure within persistent metals/chemicals and non-persistent chemicals is associated with a significant reduction in couples' fecundability. | |
| OR 0.69 (0.49–0.97) | |||||||
| Lead benzophenone-2, mBz-phthalate, mM-phthalate | OR 0.80 (0.67–0.97) | ||||||
| OR 0.81 (0.70–0.94) | |||||||
OR: odds ratio, CI: confidence interval, T: testosterone, SHBG: sex hormone binding globulin, TTP: time to pregnancy, TR: TTP ratio, FR: fecundability ratio, SD: standard deviation, IVF: in-vitro fertilization, aOR: adjusted odds ratio, IUI: intra-uterine insemination, DDT: dichloro-diphenyl-trichloroethane.