There are a lot of good reasons to get enough sleep at night (meaning 7-9 hours for adults). Being sleep-deprived impairs daytime alertness and memory; it leads to mood problems such as anxiety or sadness; it impairs the immune system; and promotes obesity and diabetes. Getting a good night’s sleep, in other words, is one of the best things you can do for your health. But here’s a reason that a lot of guys don’t know about: there’s a direct connection between the amount of sleep you get and your testosterone levels.
Most guys don’t realize that testosterone is only produced by the testicles at night. Specifically, testosterone is produced in bursts that seem to coincide with the phase of sleep that comes just before Rapid-Eye Movement (REM) sleep. REM sleep itself comes in bursts, which usually last longer as the night progresses. Testosterone levels gradually build up over the course of the night, which is why testosterone levels are highest in the morning and lowest in the evening.
Research has shown that this nightly testosterone replenishment is most effective (and morning testosterone levels are highest) in men getting 8 or more hours of sleep. Testosterone levels declined significantly when men got only between 4 and 6 hours of sleep and were very significantly reduced in men getting 4 hours or less sleep nightly.
This is an important issue because, as a society, we are chronically sleep-deprived. The average US adult gets less than 7 hours of sleep a night and more than one-third of adults report daytime sleepiness so severe that it interferes with work or social functioning at least a few days each month. Many people also are forced to work during periods that they would normally be sleeping, which can disrupt the natural cycles and phases of sleep.
Research indicates that the key variable in testosterone production is the total amount of sleep you get over the course of a night, even if the sleep is punctuated by awakenings. This suggests that even if a guy is getting up several times in the middle of the night, his testosterone production won’t be harmed as long as he’s able to fall back to sleep quickly, and as long as he still gets between 7-9 hours of sleep.
Bottom line: if you care about your testosterone levels, pay attention to your “sleep hygiene.” If you’re not sleeping well, or sleeping enough, talk to a health-care provider or see if you can make changes (such as cutting back on caffeine) that will let you enjoy all of the benefits of a decent night’s sleep.