Study Finds Possible Link Between Male Infertility and Cancer

A new study from Sweden suggests a potential link between male infertility and an increased risk of certain cancers, including thyroid and colorectal cancer, prompting renewed attention to infertility as a possible early warning sign of broader health concerns.

The research, published in the journal Human Reproduction, analyzed data from over 20,000 Swedish men diagnosed with infertility between 1994 and 2014. Compared to the general male population, these men showed a modest but statistically significant elevation in cancer incidence over an average follow-up period of nearly 12 years.

Specifically, infertile men had a 20% higher risk of developing thyroid cancer and a 15% increased risk of colorectal cancer. No significant associations were found with prostate or testicular cancer in this cohort. The findings remained after adjusting for age, education level, and socioeconomic status, suggesting the link is not solely explained by differences in healthcare access or lifestyle factors.

Dr. Yahia Al-Jebari, lead author of the study and researcher at Lund University, emphasized that while the observed associations are meaningful at the population level, they do not imply causation. “Infertility itself is unlikely to directly cause cancer,” he stated. “Instead, it may reflect underlying biological vulnerabilities — such as genetic predispositions, hormonal imbalances, or environmental exposures — that contribute to both conditions.”

This perspective aligns with growing evidence that reproductive health can serve as a biomarker for systemic health. Previous studies have linked male infertility to increased risks of cardiovascular disease, metabolic disorders, and certain autoimmune conditions. The current study adds cancer to this evolving list of potential long-term health implications.

Experts caution against overinterpreting the results. Dr. Eleanor Smith, an endocrinologist at Karolinska Institutet not involved in the research, noted that the absolute risk increase remains small. “For an individual man, the likelihood of developing thyroid or colorectal cancer is still low,” she explained. “But from a public health standpoint, these findings reinforce the importance of viewing infertility not just as a reproductive issue, but as a potential signal warranting broader health evaluation.”

The study did not investigate whether fertility treatments influence cancer risk. Researchers acknowledged this as a limitation, noting that assisted reproductive technologies (ART) were used by a subset of the cohort, but data on specific treatment types and durations were insufficient for analysis. Ongoing research is needed to determine whether any observed associations are influenced by infertility treatments or represent intrinsic factors related to the infertility diagnosis itself.

In Sweden, where national health registries enable long-term population-based studies, researchers have unique advantages for tracking health outcomes across decades. Similar investigations in other countries with linked medical databases could help validate these findings across more diverse populations.

For clinicians, the study supports considering a comprehensive health assessment for men presenting with infertility, particularly when planning for assisted reproduction. While routine cancer screening is not currently recommended based solely on infertility status, clinicians may use the opportunity to evaluate modifiable risk factors such as weight, smoking, alcohol use, and occupational exposures.

The research was funded by the Swedish Research Council and Lund University. No conflicts of interest were reported by the authors. As with all observational studies, the findings indicate association, not causation, and should be interpreted within the context of ongoing scientific inquiry into the interplay between reproductive and systemic health.