Questions about nicotine and male fertility usually arrive in one of two forms. Some men ask whether smoking affects sperm, and others ask whether switching to a vape changes the picture. The research gives partial answers to both.
What studies of smoking show
A 2019 systematic review and meta-analysis in BMC Public Health, led by Pravesh Kumar Bundhun, pooled 16 studies covering 10,823 infertile men, of whom 5,257 were smokers and 5,566 non-smokers. The findings:
| Measure | Result in smokers |
| Low sperm count (oligozoospermia) | Higher risk (RR 1.29, 95% CI 1.05 to 1.59) |
| Abnormal sperm shape | Higher (mean difference 2.44, 95% CI 0.99 to 3.89) |
| Motility | No significant difference (RR 1.42, 95% CI 0.97 to 2.09) |
The authors found head, neck and tail defects were each more common among smokers. Motility did not reach statistical significance in this analysis.
A limit on what this tells us
The review studied men already seeking treatment for infertility, and it examined tobacco smoking, which contains thousands of compounds. A cigarette’s effect on sperm can’t be assigned to nicotine alone. Studies that isolate nicotine are harder to run in humans, which is why most evidence comes from smoking or from vaping.
Vaping versus smoking
A 2025 study in Scientific Reports from researchers at CHA University in South Korea compared 151 conventional cigarette smokers with 145 e-cigarette users. All their female partners were non-smokers, and the data came from IVF and ICSI cycles between May 2022 and January 2024.
The results were mixed:
- Sperm motility was higher in the e-cigarette group
- Sperm concentration was higher in the conventional cigarette group
- Clinical miscarriage was 36% in the cigarette group and 12% in the e-cigarette group
- Live birth was 56% in the e-cigarette group and 41% in the cigarette group
The study had no non-smoking comparison group, and the authors said further research is needed to compare vaping against non-smokers. Men with significant medical histories or prior abnormal semen analyses were excluded. So the study compares vaping with smoking and leaves open whether vaping is harmless.
What the studies leave open
Several questions remain:
- How much nicotine on its own contributes, apart from other compounds in smoke
- Whether the differences seen with vaping persist in larger or non-clinic populations
- How quickly sperm quality recovers after stopping
- Whether other nicotine products, such as pouches, behave the same way
Reading the numbers
A relative risk of 1.29 means smokers in the pooled studies had about 29% higher risk of low sperm count than non-smokers. That’s an average across studies and says nothing certain about any one man. A man with a normal semen analysis who smokes still has a normal result, and a non-smoker can have a low count for unrelated reasons.
The confidence interval of 1.05 to 1.59 shows the estimate is imprecise. The lower bound sits close to 1, which would mean almost no difference.
Practical steps for a couple trying to conceive
Men who smoke or vape and are trying to start a family can raise it with a doctor early. A semen analysis measures concentration, motility and shape, giving a baseline. Where results are low, a doctor may suggest repeat testing and lifestyle changes before further investigation.
Those asking does nicotine affect sperm will find the evidence points in one direction for smoking: the meta-analysis links it to a higher risk of low count and abnormal shape. For vaping the evidence is thinner and the comparison group is smokers.
What the vaping study can and can’t support
The South Korean study drew its data from couples already in IVF or ICSI treatment, and it excluded couples with other infertility factors. Results from that group may not apply to men conceiving without treatment. The miscarriage gap, 36% against 12%, is large but comes from a small sample of 296 men, so the authors call for more research.
Readers weighing the two habits should treat the study as one data point. It suggests vaping may carry a lower risk than smoking for some outcomes, and it can’t say vaping is safe for fertility.
Other factors that go with it
Smoking rarely travels alone. Alcohol use, sleep, weight and heat exposure also affect semen, and a couple’s fertility depends on both partners. A fertility specialist usually checks all of these rather than one in isolation.
If a man decides to stop, the sensible next step is to book a semen analysis before stopping and another afterward, so the change can be compared against a baseline.
