November 9, 2026, 5:01 pm | Read time: 6 minutes
Obstructive sleep apnea (OSA) is a sleep-related disorder known for causing nighttime breathing interruptions. Daytime fatigue is one of the accompanying symptoms of this breathing disorder. Additionally, it can have other, sometimes serious, health consequences, including an increased risk of cardiovascular diseases for those affected. A new study now shows potential impacts in another area: In affected men, sperm motility and semen volume may be reduced. Researchers also found elevated inflammation levels directly in the seminal fluid. What might these results mean? FITBOOK spoke with experts.
Sleep and Sperm–a Known Connection
A connection between sleep and sperm quality has often been the subject of research. FITBOOK has reported on studies that provided evidence suggesting that chronically poor or irregular sleep is associated with lower sperm quality. To clarify: The studies examined different aspects, from sleep duration to frequent sleep interruptions–“poor sleep” is not simply equated with sleep deprivation.
Among other things, lower sperm concentrations, reduced sperm motility, and decreased semen volume were observed.1, 2 A meta-analysis from 2022 confirmed this connection.3 However, the exact biological mechanisms behind this are not yet fully understood. This is where the new study comes in, focusing on obstructive sleep apnea (OSA), referred to simply as sleep apnea hereafter.4
Study on Sleep Apnea and Sperm Quality
In people with sleep apnea, the upper airways can repeatedly narrow or close during sleep. This leads to the typical breathing interruptions, which can cause sleep disruptions and temporary oxygen deprivation in the brain of those affected. FITBOOK delves deeper into the possible causes, symptoms, and consequences of sleep apnea in this article.
It is known that these stresses can promote inflammatory processes in the body and, in turn, cardiovascular diseases. However, the potential impacts on male fertility are less researched. Existing studies on the topic have primarily focused on erectile dysfunction and changes in testosterone levels.5
The authors of the current study examined the relationship between sleep apnea, various parameters of sperm quality, erectile function, and inflammatory markers in the blood and seminal fluid. They were particularly interested in the potential role of inflammatory mediators, known as cytokines. These are signaling molecules involved in regulating immune responses and inflammatory processes.
Details of the Study
For the study, researchers followed participants over an extended period. They first examined the differences between men with and without sleep apnea. They then observed how the values of sleep apnea patients developed during CPAP treatment. CPAP is a common therapy for sleep apnea that involves wearing a breathing mask at night. Through the associated device, patients are continuously supplied with air under slight pressure, keeping the airways open.
The study was conducted between October 2022 and December 2024 at the Sleep Medicine Center of the University of Hong Kong-Shenzhen Hospital. A total of 94 men of reproductive age participated. They were divided into two groups based on the results of a sleep analysis: 72 men with obstructive sleep apnea and 22 men without the condition.
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Data Collection on Sperm Quality and Erectile Function
Various semen parameters were recorded, including semen volume and the total and progressive motility of sperm. Progressive motility describes the direction and quality of sperm cell movement.
Erectile function was also considered in the analysis. For this purpose, participants completed the standardized IIEF-5 questionnaire, which helps identify potential impairments in erectile ability. Additionally, researchers examined both blood serum and seminal fluid of study participants for inflammatory mediators.
Sleep quality and any breathing interruptions were examined for group classification at the beginning. During the subsequent CPAP treatment, researchers tracked the development of semen quality and other measured values. Whether participants regularly used their breathing mask and how well the treatment worked can be checked in the data stored on the device. This includes the so-called apnea-hypopnea index (AHI), which indicates how many breathing interruptions and phases with significantly reduced airflow occur per hour.
Results
Several differences in semen quality were observed between the 72 men in the sleep apnea group and the control group. Their total and progressive sperm motility were significantly lower, and their semen volume was also reduced.
The authors describe the observed differences in inflammatory markers as particularly noteworthy. They found elevated concentrations of four cytokines (IL-1β, IL-6, IL-10, and IL-17A) in the seminal fluid of those with sleep apnea. Interestingly, no corresponding changes were found in the examined blood serum. Similarly, there were no significant differences in erectile function between the two groups.
An important finding emerged during the CPAP treatment. In men who consistently wore their breathing mask, progressive sperm motility improved quite quickly–sometimes as early as one month after starting treatment.
Also notable: The more disrupted the REM sleep was, the poorer the semen quality. REM stands for “Rapid Eye Movement”–this sleep phase is known for rapid eye movements that can be visible even through closed eyelids. Additionally, independently of this, elevated levels of the inflammatory mediators IL-1β and IL-6 in the seminal fluid were associated with lower sperm quality.
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Significance of the Results
The results suggest a connection between sleep disorders, local inflammatory processes, and reduced sperm motility. This study expands the current understanding of the potential health consequences of obstructive sleep apnea.
Particularly interesting is the indication of possible local inflammatory reactions in the male reproductive tract, as these occurred independently of inflammatory processes in the rest of the body. This may have potential for therapeutic practice. In the future, sleep-related breathing disorders could be more strongly considered as a possible cause of unexplained abnormalities in sperm analysis.
It was also interesting that in men who consistently used their CPAP therapy, progressive sperm motility improved so quickly. Researchers interpret this as a possible positive effect of sleep apnea treatment on reproductive function. However, it is not yet proven that CPAP increases fertility or even the chances of becoming a father. Only semen parameters were examined.
Limitations
Despite the promising results, certain limitations should be considered when interpreting the study. Among other things, the number of participants was relatively small, with a total of 94 men, and in an unequal ratio–only 22 of them did not suffer from sleep apnea. Furthermore, sleep measurement was only conducted at the beginning of the study, so changes in sleep quality during CPAP treatment could not be captured.
Additionally, the study was not conducted under randomized, controlled conditions. Therefore, the observations do not prove that CPAP treatment alone was responsible for the improvements in sperm motility. It also cannot be definitively stated whether the elevated inflammation levels actually caused the poorer semen quality. Initially, the study can only show correlations, not established cause-and-effect relationships.