Male patients who suffer from obstructive sleep apnea (OSA) -- the inability to breathe properly during sleep -- produce lower levels of testosterone, resulting in decreased libido and sexual activity, according to researchers at the Technion-Israel Institute of Technology. Previous studies had indicated that male sleep apnea patients had reported decreased libidos but the studies were unable to establish a scientific link. The current study, reported in the July issue of The Journal of Clinical Endocrinology & Metabolism, found that nearly half the subjects who suffered from severe sleep apnea also secreted abnormally low levels of testosterone throughout the night.

Sleep apnea is a respiratory disorder that affects 4%-9% of adult males. Its most common manifestation is loud snoring and it may occur several hundred times throughout the night, resulting in sleep fragmentation and excessive daytime sleepiness. For many years sleep apnea sufferers have complained of decreased libidos, yet previous studies reported that patients' testosterone levels, although low, were within the normal adult male range.

The current study adopted a different methodology. Earlier studies had only measured participants' testosterone levels once after awakening. In this study, subjects were admitted to the Technion Sleep Center for an entire night and were fitted with electrodes and catheters. They were monitored between 7 p.m. and 7 a.m. with blood samples collected every 20 minutes. At 10 p.m., lights were turned off and the participants retired to sleep. Two groups -- one of sleep apnea patients and another of normal controls of similar body weight and age -- were investigated.

The study found that nearly half the sleep apnea patients secreted abnormally low testosterone levels throughout the night.

The Technion-Israel Institute of Technology is Israel's leading scientific and technological center for applied research and education. It commands a worldwide reputation for its pioneering work in computer science, biotechnology, water-resource management, materials engineering, aerospace and medicine. The majority of the founders and managers of Israel's high-tech companies are alumni.