sleep.
Researchers at the University of Chicago concluded that the few hours of sleep significantly reduce testosterone levels, thereby falling libido and reproduction of even the young men.
Specifically, five hours of sleep reduces testosterone levels to 10-15%, a rate not insignificant, considering that increasing age at a time deprives hormone levels only 1 to 2% as a result of the aging body.
A week of bad sleep, then, can throw the testosterone a man 25 years to levels exceeding the one in 15 years!
