Matthew Walker dropped a brutal fact: Men who sleep only 5 hours a night have significantly smaller testicles than those who get 7 hours.
He also said men sleeping 4–5 hours have testosterone levels equivalent to someone 10 years older. And the same lack of sleep impairs female reproductive health.
A 2011 study published in the Journal of the American Medical Association found that young healthy men who slept only 5 hours per night for one week experienced a 10–15% drop in daytime testosterone levels.
Other research has linked chronic short sleep to reduced testicular size, lower sperm quality, and disrupted female reproductive hormones (including menstrual cycle irregularities and reduced fertility).
Sleep is doing way more heavy lifting for your hormones than most people realize.
How many hours are you actually sleeping most nights?