Sleep loss lowers testosterone in healthy young men

Reduced amounts of sleep drastically lower a healthy young man’s testosterone levels, according to a recent study published as a research letter in JAMA (2011; 305: 2173-4).

Senior author Eve Van Cauter, PhD, of the University of Chicago, found that men who slept less than 5 hours per night for 1 week in a laboratory had significantly lower levels of testosterone than when they had a full night’s sleep.

"Low testosterone levels are associated with reduced well being and vigor, which may also occur as a consequence of sleep loss," Dr. Van Cauter said. "As research progresses, low sleep duration and poor sleep quality are increasingly recognized as endocrine disruptors."

For the study, 10 young men (average age, 24 years) were recruited from around the University of Chicago campus. They passed a rigorous battery of tests to screen for endocrine or psychiatric disorders and sleep problems.

The participants spent 3 nights in the laboratory sleeping for up to 10 hours, followed by 8 nights sleeping less than 5 hours. Their blood was sampled every 15 to 30 minutes for 24 hours during the last day of the 10-hour sleep phase and the last day of the 5-hour sleep phase.

The effects of sleep loss on testosterone levels were apparent after just 1 week of short sleep. Five hours of sleep decreased their testosterone levels by 10% to 15%. The men had the lowest testosterone levels in the afternoons on their sleep-restricted days, between 2 p.m. and 10 p.m. The results indicate that skipping sleep reduces a young man’s testosterone levels by the same amount as aging 10 to 15 years.

The men also reported a decline in their sense of well being as their blood testosterone levels declined. Their mood and vigor fell more every day as the sleep restriction part of the study progressed.