Oxygen deprivation may contribute to male infertility

Medical conditions that deprive the testes of oxygen, such as sleep apnoea, may be contributing to the decline in male fertility observed over the past 50 years, according to a new study.

Published in Nature Review Urology, the literary review examined findings from multiple studies to holistically capture the causes and effects of testicular hypoxia in various scenarios. The review was led by reproductive biologist Dr Tessa Lord, from the University of Newcastle and the Hunter Medical Research Institute (HMRI).

Lord explained that a lack of oxygen in the testes can negatively impact sperm count and quality by disrupting hormone production and gene expression. When testis hypoxia is caused by chronic medical conditions — such as sleep apnoea or varicocele — there is a sustained threat to reproductive health.

Varicocele, or enlarged veins in the scrotum, is a common abnormality which is diagnosed as the cause of infertility in up to 45% of men who are struggling to conceive, while obstructive sleep apnoea affects 13–30% of the male population. Several studies have shown correlation between sleep apnoea and infertility in males, but Lord said we urgently need further research to understand the direct effects on sperm production and quality.

Lord added that high-altitude activities such as hiking can cause lack of oxygen in the testis, although any impaired fertility is generally reversible once more oxygen is restored in the body. This can take a few months to resolve, she noted.

Lord is now calling for greater public and clinical awareness of the reproductive risks associated with sustained testicular hypoxia, stating that the timely management of conditions like varicocele and sleep apnoea could help mitigate and even reverse the associated fertility risks. She added that the rise in prevalence of conditions such as sleep apnoea, combined with potential intergenerational effects, makes testicular hypoxia a critical issue in understanding male fertility trends.

“We know male fertility has declined significantly over the past 50 years,” Lord said.

“Emerging evidence suggests that testis hypoxia in fathers could result in embryos with developmental issues, and those children could grow up to experience fertility issues themselves.”

Lord conceded that significant knowledge gaps in science remain, stating that further research is needed to fully grasp the broader implications of these findings and to develop effective interventions.

“We need to improve fertility outcomes today and also help safeguard the reproductive health of generations to come,” she said.

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