Dr. David Gozal, a professor of Paediatrics at the University of Louisville, says that the link between the two conditions can be due to the chronic intermittent hypoxia (CIH)-oxygen deprivation-that sleep apnea sufferers often exerience during episodes of obstructed breathing.
He has revealed that mice exposed to CIH, similar to that which a human with PSAS would experience, showed a 55 per cent decline in their daily spontaneous erections when studied after one week.
"Even relatively short periods of CIH...are associated with significant effects on sexual activity and erectile function," says Dr. Gozal.
After five weeks of CIFH exposure, the "latency to mount" period- the average interval between mounting a mate- increased 60-fold, and latency to intromission increased by 40-fold. Latency to ejaculation was also severely affected.
In five out of seven mice tested, ejaculation did not occur at all, but in one mouse and latency to ejaculation was eleven hours, while in control mice the median time to ejaculation was "only a few minutes.
One mouse appeared to be unaffected in this respect.
"The disparity in responses among mice is very similar to the heterogeneity of the magnitude of end-organ morbidity in sleep apnea among patients, and shows that not everyone will be affected to the same extent," said Dr. Gozal.
In another experiment, the researchers treated the mice with tadalafil that increases the availability of nitric oxide through PDE5, and the treatment improved erectile and sexual functioning in CIH-exposed mice to near-normal levels in almost all cases.
"In the present study, tadalafil restored CIH-induced impairments of latencies to mounts, intromissions and ejaculations, significantly improving performance during spontaneous erections and during mating and non-contact activity. The effects of tadalafil were not limited to the erectile tissue but extended to behavioural components, suggesting a possible role for PDE5 in central nervous system mechanisms that control sexual behaviour," wrote Dr. Gozal
"Further studies are needed to explore the effects of sleep disruption and episodic hypoxia during sleep on the central nervous system that mediates sexual drive. Exploration of alternative interventions aiming at preventing and treating this infrequently spoken of, yet extremely frequent complication of OSA, will certainly require improved understanding of the complex mechanisms affecting sexual activity and how it is affected by diseases such as sleep apnea," said Dr. Gozal.
John Heffner, past president of the ATS, said: "These findings add sexual dysfunction to a long list of disorders associated with - and probably caused by - OSA. Although this study was performed in research animals, chronic intermittent hypoxia has profound effects on multiple organ systems and a strong biologic plausibility exists that similar findings will be observed in humans. Early identification and effective therapy of OSA is critically important especially considering the high prevalence of this disorder."
The results have been published in the American Journal of Respiratory and Critical Care Medicine, a publication of the American Thoracic Society.