Lack of sleep reduces testosterone in men

CHICAGO, May 31 (UPI) -- Men sleeping less than 5 hours a night for one week had significantly lower levels of testosterone than if they had a full night's sleep, U.S. researchers say.

Eve Van Cauter of the University of Chicago says low testosterone has a host of negative consequences for young men and not just in sexual behavior and reproduction -- is it associated with low energy, reduced libido, poor concentration and fatigue -- but in building strength and muscle mass and bone density.

The 10 young men -- average age 24 -- in the study passed a rigorous battery of tests to screen for endocrine or psychiatric disorders and sleep problems, who were lean and in good health.

The men spent three nights in the laboratory sleeping for up to 10 hours, and then eight 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 five-hour sleep phase.

The men with the lower levels of testosterone reported a decline in their sense of well-being and their mood and vigor fell more every day as the sleep restriction part of the study progressed, Cauter says.

The findings are scheduled to be published in the Journal of the American Medical Association.