Smoking followed with a 2.36-fold increased risk, while men who combined multiple habits—smoking/chewing tobacco and alcohol—were 2.84 times more likely to exhibit damaged sperm.
Published Oct 16, 2025 | 7:00 AM ⚊ Updated Oct 16, 2025 | 7:00 AM
Synopsis: A new study from Karnataka has found that Indian men who chew tobacco face more than four times the risk of sperm damage and impaired fertility compared with non-users. Published in Oncoscience, the research linked tobacco use, along with alcohol consumption, excess body weight, and occupational heat exposure, to reduced sperm count, motility, and DNA integrity. The authors emphasised that the findings indicate correlation rather than causation and called for a comprehensive approach to assessing male infertility.
Men who chew tobacco face more than four times the risk of impaired fertility compared to those who do not have the habit, according to a recently published cross-sectional study that examined 278 men at an infertility clinic in Karnataka.
The study, titled Lifestyle and hormonal factors affecting semen quality and sperm DNA integrity, appeared in the September 2025 issue of Oncoscience.
Conducted by researchers at the KLE Academy of Higher Education and Research in Belagavi, Karnataka, the study found that tobacco chewing showed the strongest association with altered semen parameters, increasing the odds by 4.22 times.
Smoking followed with a 2.36-fold increased risk, while men who combined multiple habits—smoking/chewing tobacco and alcohol—were 2.84 times more likely to exhibit damaged sperm.
The research shows that male infertility in this population stems largely from preventable and modifiable risk factors, underscoring the need for lifestyle changes among individuals facing fertility challenges.
The data showed marked differences between tobacco users and non-users. Men in the altered semen parameter group who consumed tobacco had a mean sperm concentration of 31.94 million per millilitre, compared to 98.47 million per millilitre in the normal group. Sperm motility dropped to 45.03 percent versus 77.2 percent in healthy participants, indicating that tobacco exposure affects several aspects of sperm function.
Alcohol consumption presented a similar pattern. Men with altered semen profiles recorded sperm concentrations of 28.63 million per millilitre compared with 91.06 million per millilitre in the normal group. Motility and progressive motility both declined, while sperm DNA fragmentation rose among alcohol consumers with altered profiles.
The combination of habits compounded the damage. Men who reported smoking, drinking alcohol, and chewing tobacco simultaneously showed lower sperm concentration, total count, and motility across all parameters. Head defects occurred more frequently, while sperm DNA fragmentation trended toward significance.
“Tobacco use was associated with reductions in sperm concentration, motility, morphology, and total sperm count, consistent with the findings of Henriques et al. (2023), who attributed these effects to tobacco-induced oxidative stress,” the authors wrote.
Age emerged as another factor affecting fertility, though in unexpected ways. The study found that advancing male age correlated with higher sperm DNA fragmentation, even though traditional semen parameters such as concentration, motility, and shape did not vary across age groups. Men over 40 years showed markedly higher DNA fragmentation, while younger men aged 21 to 30 years had lower fragmentation levels.
Participants aged 31 to 40 years formed the largest group in both normal and altered semen profile categories, accounting for 65.5 percent and 61.65 percent respectively. The data showed that age alone did not affect conventional semen quality metrics but impaired the genetic quality crucial for conception and embryo development.
“A significant association was observed between advanced paternal age and elevated sperm DNA fragmentation, despite preserved conventional semen parameters,” the authors noted.
“This aligns with the meta-analysis by Szabó et al. (2023), who identified paternal age greater than 50 years as a contributor to increased sperm DNA fragmentation. These findings indicate that while semen concentration, motility, and morphology may remain within reference limits, genomic integrity declines with advancing age.”
Body weight played a role as well. The study found that 59.7 percent of participants had a normal body mass index, while 29.9 percent were overweight and 9.7 percent were underweight. Both overweight and underweight men showed poorer semen profiles than those with normal body mass index.
Men with altered body mass index showed reduced sperm concentration at 70.21 million per millilitre versus 95.34 million per millilitre, total sperm count at 150.76 million versus 210.45 million, motility at 61.33 percent versus 78.12 percent, and progressive motility at 38.64 percent versus 52.34 percent. Sperm DNA fragmentation was higher in the altered body mass index group at 0.49 versus 0.38, reinforcing the link between metabolic imbalance and impaired sperm production.
Occupational heat exposure also affected sperm DNA integrity. Among men with documented heat exposure, 61.9 percent had elevated sperm DNA fragmentation compared to 46.9 percent among those without exposure. Physical activity did not show a relationship with semen parameters or DNA fragmentation.
“Occupational heat exposure was strongly associated with elevated sperm DNA fragmentation, supporting the evidence that thermal stress induces oxidative damage and chromatin instability in spermatozoa,” the researchers explained.
The hormonal analysis revealed associations between testosterone, prolactin, and anti-Müllerian hormone and semen quality. Low testosterone concentrations were linked to abnormal semen profiles, while high prolactin levels correlated with altered diagnostic status.
Anti-Müllerian hormone levels showed a distinctive pattern: low levels were associated with elevated sperm DNA fragmentation, indicating that Sertoli cell function may help maintain sperm chromatin stability.
“Anti-Müllerian hormone has emerged as a novel biomarker for sperm DNA integrity, with low levels being more prevalent in men with DNA fragmentation,” the authors stated. “This finding suggests that Sertoli cell dysfunction, as reflected by anti-Müllerian hormone production, may play a role in maintaining chromatin stability during spermiogenesis.”
Other hormones, including follicle-stimulating hormone, luteinising hormone, oestradiol, inhibin B, and thyroid-stimulating hormone, did not show associations with semen parameters or DNA fragmentation. The findings suggest that targeted hormonal evaluation focusing on testosterone, prolactin, and anti-Müllerian hormone may offer better insight into male reproductive potential.
The dietary analysis showed that most participants consumed tea daily, with one-third consuming dairy products daily and about 40 percent consuming fruits or vegetables four to six times a week.
Nearly 80 percent of participants drank tea every day, over 40 percent ate vegetables four to six times weekly, and nearly 40 percent consumed fruits daily. The study also noted frequent consumption of smoked or grilled foods, which may expose individuals to polycyclic aromatic hydrocarbons associated with oxidative stress.
The study enrolled 293 male patients initially and excluded 15 with azoospermia. Of the remaining 278 participants, 145 (52.2 percent) had normal semen parameters, while 133 (47.8 percent) had altered parameters.
The research followed World Health Organisation (WHO) sixth edition guidelines for semen analysis, evaluating parameters such as sperm count, motility, and shape.
The findings were based on data collected between March 2023 and March 2024 at a tertiary care infertility clinic, where researchers analysed semen samples from men aged 21 to 50 years.
The team assessed conventional measures such as sperm count, motility, and shape, along with sperm DNA fragmentation, a molecular indicator of genetic damage linked to reduced fertility outcomes.
“This study aimed to comprehensively explore the associations between lifestyle factors, hormonal levels, and male reproductive outcomes, specifically focusing on conventional semen parameters and sperm DNA fragmentation in an Indian population sample,” the authors stated.
“Our findings provide insights into the limited data available on this demographic and highlight both modifiable and intrinsic risk factors affecting fertility in men.”
The researchers emphasised that semen parameters can appear normal even when sperm DNA integrity is compromised. The Sperm Chromatin Dispersion test used in the study provided quantitative evidence of DNA damage linked to age, lifestyle, and hormonal status.
“Considering the comprehensive results and analyses, this study provides clinical evidence linking modifiable lifestyle factors, hormonal imbalances, and advanced paternal age with impaired semen quality and elevated sperm DNA fragmentation,” the authors concluded. “The application of the WHO sixth edition semen analysis criteria enhances the relevance of these findings to current diagnostic standards.”
The research team noted that their findings demonstrate correlations rather than causation. Confounders such as genetic predisposition, unmeasured environmental exposures, or concurrent subclinical conditions may play roles. They acknowledged that causality cannot be confirmed without longitudinal or interventional studies.
“These results support the need for an integrative approach to male infertility assessment, including routine lifestyle evaluation, hormonal profiling, and sperm DNA fragmentation testing,” the authors stated. “Such a multidimensional strategy can improve diagnostic accuracy, inform personalised treatment plans, and enhance the success rates of assisted reproductive technologies.”
The biological mechanisms underlying these associations involve multiple factors. Tobacco and alcohol consumption induce oxidative stress, mitochondrial dysfunction, and DNA strand breakage. Heat exposure and body mass index dysregulation increase reactive oxygen species production and impair sperm production.
Hormonal imbalances, particularly low testosterone and anti-Müllerian hormone levels combined with elevated prolactin, indicate disruption of the hypothalamic-pituitary-gonadal axis and Sertoli cell dysfunction, which compromise chromatin packaging and DNA stability.
(Edited by Dese Gowda)
