Deep sleep is the portion of a nights rest when the body repairs itself and the brain organizes information acquired during the day. It is, in other words, one of the most important segments of sleep for daily rejuvenation. Young men devote about 10 to 20 percent of their sleep to deep sleep, but after age 50, deep sleep falls to five to seven percent of total sleep. Men over the age of 60 can even have no deep sleep at all. The reason? A University of Montreal researcher believes decreasing testosterone levels may be the culprit.
While the link is still tenuous, Zoran Sekerovic, a graduate student from the universitys department of psychology, has found a connection between testosterone levels and sleep quality. That may be because testosterone influences brain circuitry. "With age, there is neuronal loss and the synchronization of cerebral activity isn't as good, which is why there is a loss of deep sleep. Because deep sleep requires great synchronization," says Sekerovic. "Low levels of testosterone intensify the lack of synchronization and can explain 20 percent of men's inability to experience deep sleep."
Other researchers have concluded the reverse, that lack of deep sleep impacts testosterone levels, but Sekerovic notes that previous studies looked at fluctuations in testosterone, which is higher in the morning. If, as he believes, its the other way around and testosterone impacts deep sleep, it may open the door to a debate about hormone therapy. "The loss of deep sleep is a serious problem that could be treated with testosterone. That would be tremendous progress," says Sekerovic. "But hormone therapy can have secondary effects. Therefore, it will be essential to better understand the mechanisms leading to the loss of deep sleep."
