Not making the kind of gains you want in the gym? Your diet and training maybe flawless but there is one variable that may be missing: sleep. Two studies have recently correlated resting testosterone with the amount of sleep in men1, 2. Researchers have speculated that the use of the internet at night, late night television, and sleeping with your cell phone that goes off all night long can compromise normal sleep rhythms of many young men. Many Americans are sleeping less than the recommended 8 hours per night3; interestingly sleep also decreases with age. Plasma testosterone levels vary in a circadian manner, higher on waking and decreasing to a low point at the end of the day. Superimposed on this are burst‑like increases in testosterone production that occur every 90 min or so7, 8. Plasma testosterone levels begin to rise with the onset of sleep, and in young men peak at the first REM sleep episode and remaining at that level until waking9; the longer the REM sleep latency, the slower the rise in testosterone. More recently it has become apparent that the production of testosterone is dependent on sleep reaching the peak during the first three hours of uninterrupted sleep, and at least in young men at about the time of the first REM episode10. Total fragmentation of normal sleep architecture throughout the night prevents the increase in testosterone11. It has also been shown, at least in young men, that the sleep‑dependent increase in testosterone occurs irrespective of whether the sleep occurs at night or for an equivalent duration during the day. The increase in testosterone with sleep time and a decrease in time awake is stable within an individual, but in turn, there are large individual differences12. Testosterone is not subject to circadian variation, in the same way, that cortisol. There is a sleep‑dependent increase in testosterone that requires 3 hours of slow wave sleep or perhaps a bit longer with increasing age. Testosterone remains elevated for the duration of sleep. The subsequent decrease in testosterone depends on the duration of wakefulness; decreasing more with prolonged wakefulness13. Based on several studies, sleep has more of an impact on testosterone levels than previously thought. Researchers from China collected the blood from 531 Asian males between the ages of 29 and 70. Researchers collected questionnaires and sleep habits of the men as well. The researchers found that many men above age 50 years of age were sleeping less than 6 hours a night compared to men in their 40’s. The researchers found that the less men slept, the lower their serum testosterone tended to be. There was a direct correlation between sleep and testosterone levels; this finding was independent of age, total body fat, and exercise intensity7. It was previously reported that men who slept between 4-6 hours had lower testosterone levels than man who slept more than 8 hours4, 5. In this study, the relationship between sleep loss and testosterone and free testosterone (bioavailable testosterone) were lower in men who slept for between 4 – 6 hours than those who slept more than 6 hours give credence to the suggestion that man who sleep less than 6 hours a night have lower testosterone and free testosterone than those who sleep more than 6 hours. An adequate nightly sleep is a key component of man’s recuperation process following a day’s work. This recuperation process is the engine for the regeneration of alertness required for optimal cognitive and physical functional capacities. The current study mentioned was the observation that total testosterone and bioavailable testosterone were highest in men who slept between 6h to 8h or more gives my support to an earlier study that the optimal sleep duration is about 8h6. Some athletes may only sleep 6 hours a night, but based on the current study men who slept less than 6 hours of sleep had less serum testosterone production than the men who slept 8 hours of sleep a night.
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