Healthcare (Commonwealth Union) – Health conditions that limit oxygen supply to the testes, such as sleep apnea, could be contributing to the decline in male fertility observed over the past five decades, according to a new study.
Appearing in the journal Nature Reviews Urology, the review examines how factors like sleep apnea, varicocele, and exposure to high altitudes affect sperm quality and male reproductive health.
The research was led by Dr. Tessa Lord, a reproductive biologist and Senior Lecturer at the University of Newcastle, who is also part of HMRI’s Infertility and Reproduction Research Program.
Dr. Lord indicated that conditions such as varicocele and sleep apnea lower the amount of oxygen-rich blood reaching the testes, a state known as testis hypoxia.
She further pointed out that previous studies have shown that testis hypoxia can harm sperm count and quality by interfering with hormone production and gene expression.
The review analyzed data from multiple studies to comprehensively understand the causes and consequences of testicular hypoxia in different contexts.
Dr. Lord explained that when oxygen deprivation in the testes results from chronic health conditions—such as sleep apnea or varicocele—it poses a persistent risk to reproductive function.
Dr. Lord stated that varicocele, a condition involving enlarged veins in the scrotum, is a frequent abnormality and is identified as the cause of infertility in up to 45 percent of men experiencing difficulties conceiving.
She also pointed out that obstructive sleep apnea is the most prevalent sleep-related breathing disorder, affecting between 13 percent and 30 percent of men. Its prevalence is rising, largely due to the increasing rates of obesity, a major risk factor.
Several studies have linked sleep apnea to male infertility, but Dr. Lord emphasized the urgent need for further research to determine its direct impact on sperm production and quality.
Dr. Lord also noted that while high-altitude activities like hiking can lead to reduced oxygen levels in the testes (hypoxia), the effects on fertility are typically temporary.
Dr. Lord emphasized that the positive news for hikers is that any fertility issues caused by high-altitude conditions are usually reversible once normal oxygen levels are restored in the body.
She indicated however, that this recovery can take several months after returning to lower altitudes.
Dr. Lord is advocating for increased awareness—both among the public and within the medical community—about the reproductive risks linked to prolonged testicular hypoxia.
She pointed out that effectively managing conditions such as varicocele and sleep apnea in a timely manner could help reduce associated fertility risks.
She went on to indicate that there is encouraging evidence suggesting that fertility issues caused by hypoxia may be reversible if the root cause is properly treated.
Researchers of the study pointed out that male infertility is defined as the inability to conceive after 12 months or more of consistent, unprotected sex, while sub-fertility refers to a milder form of reproductive impairment that can still decrease the chances of conception.
The increasing prevalence of conditions like sleep apnea, along with potential intergenerational effects, highlights testicular hypoxia as a key factor in understanding trends in male fertility.
“We know male fertility has declined significantly over the past 50 years,” says Dr. Lord.
“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.”
Despite advancements in comprehending the connection between low oxygen levels and reproductive capabilities, Dr. Lord emphasized that substantial gaps in scientific knowledge still exist.
“We don’t yet have all the answers, particularly around the impact on sperm quality when there is a lack of oxygen in the testis,” added Dr. Lord further indicating that more research is needed to know the full extent of the generational impact.
