University of Louisville researchers found that, in a study of mice, one week of chronic intermittent hypoxia (CIH) -- the lack of oxygen suffered during obstructive sleep apnea syndrome (OSAS) -- resulted in a 55 percent decline in their daily spontaneous erections. After five weeks, the length of time between mice attempts at mating increased on average by 60-fold.

The findings, published in the second September issue of the American Journal of Respiratory and Critical Care Medicine, showed that when the mice went back on standard oxygen levels for six weeks, they recovered 74 percent of their original erectile function.

A second treatment using tadalafil, which is generic Cialis and increases the availability of nitric oxide, improved erectile and sexual functioning of almost all the mice to near-normal levels.

"Even relatively short periods of CIH ... are associated with significant effects on sexual activity and erectile function," Dr. David Gozal, professor of pediatrics at the University of Louisville, wrote in the article.

Researchers found no differences in levels of testosterone or other indicators related to erectile function in mice exposed to CIH for eight weeks.

"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," said John Heffner, past president of the American Thoracic Society, "Early identification and effective therapy of OSA is critically important, especially considering the high prevalence of this disorder."

More information

The American Sleep Apnea Association has more about symptoms and treatment of sleep apnea .