Less Sleep, More Bathroom Trips Aug. 8, 2007 -- Lying awake at night increases urine production -- meaning more trips to the bathroom, especially for men, Danish researchers find.

At night, urine production slows -- one of evolution's contributions to a good night's sleep.

But what happens if you can't get to sleep? To find out, Birgitte Mahler, MD, and colleagues at Aarhus University Hospital, Denmark, studied 20 healthy, young adults, 10 male and 10 female.

After standardized food and beverage intakes, each study participant spent two days and nights in the lab. On one randomly assigned night, each study participant was allowed to sleep. On the other night, they were kept awake.

On the sleepless nights, both men and women produced more urine than they did on the nights they slept. But this effect was more pronounced in the men than in the women.

Mahler and colleagues reported the findings at the American Physiological Society conference "Sex and Gender in Cardiovascular-Renal Physiology and Pathophysiology" held in Austin, Texas.

• Guys, how many nighttime bathroom breaks do you take? Tell us about it on the Men’s Health: Man-to-Man message board.