Sleep Apnea and Erectile Dysfunction

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In an experiment designed to test this hypothesis, University of Louisville researchers discovered that after seven days of exposure to CIH which resembled that in a man with obstructive sleep apnea, male mice had a fifty per cent reduction in the number of spontaneous daily erections. And after thirty five days of exposure, the time it took male mice to mount a mate had increased by a factor of sixty times.

David Gozal, MD, professor at the University of Louisville, commented that it appeared even relatively short periods of CIH could have a major impact on sexual activity and the male's ability to become erect. The research work looked at the effects on behavior and physiology of mice exposed to CIH for periods ranging from thirty five days to more than twenty weeks. A group of control mice were not exposed to the same stimulation and did not experience CIH. The mice were all examined for changes in sexual behavior, as well as the number of erections they developed and how their mating behavior was affected. A number of physiological parameters such as testosterone and estradiol levels were examined, together with endothelial and neuronal nitric oxide synthase activity. These compounds play an essential role in the mechanism of erection. These compounds are abbreviated to eNOS and nNOS; eNOS is a molecule whose levels are raised by Viagra, and it plays a major part of the male sexual physiology.

After only thirty five days' exposure to CIH, the male mice took sixty times longer to mount their partners during sexual activity, but also experienced an increase in the time between becoming aroused and penetration of about forty fold. The length of time between penetration and ejaculation was also affected, so much so that in five out of seven experimental mice, ejaculation did not take place, while in normal mice it took only a few minutes

Dr Gozal added that the variation in responses between mice mirrors the variation between men, who show very different responses to sleep apnea, and who clearly do not all experience the impact on erectile function to the same degree. There were no significant changes in testosterone and estradiol levels in the experimental mice, although there was a decrease in eNOS expression in the mice which were subjected to CIH for fifty six days.

Even more interesting, after as little as one week's exposure to sleep apnea, and a recovery period of forty two, the mice had only regained about three quarters of their original capacity for erections. This implies there is some permanent effect or that longer recovery time is required. In any even, the impact f sleep apnea on erectile function is severe, and it looks like a major cause of erectile dysfunction in men.

Given enough time, the effects of sleep apnea were reversible. Using a drug commonly prescribed for erectile dysfunction, tadalafil, which works by increasing the availability of nitric oxide through PDE5, the mice were restored to normal sexual and erectile functioning, so that the impact of CIH was almost completely reversed. This applied to all aspects of sexual behavior, including time to mount, penetration and time to ejaculation as well as number of erections and spontaneous erections. The point here being that tadalafil affected both erectile physiology and mating behavior. This could indicate that PDE5 has a role in the central nervous system control of sexual behavior.

Dr Gozal indicates that more research is needed to elucidate the relationship between sexual behavior, sexual physiology and sleep disruption and episodes of hypoxia during sleep. This is incredibly important for men with erectile dysfunction, because CIH is a very common occurrence in OSA. In summary, though, erectile dysfunction appears to be yet another dysfunction associated with - and most likely caused by - obstructive sleep apnea. And even though this work was done on mice, chronic intermittent hypoxia has some very profound impacts on multiple organ systems, which make it extremely likely that the same effects apply to humans. This means that early identification of the condition and application of some effective therapy for OSA is extremely important for regulating erectile dysfunction in men who suffer form both conditions.

This news was originally published in the Thoracic Society's peer-reviewed journal, the American Journal of Respiratory and Critical Care Medicine.
 

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