Sleeplessness: Different for Men and Women

Sure, a bad night’s sleep can make you miserable. But over the long haul, too little sleep can have consequences that go way beyond nodding off at a meeting or snapping at your spouse.

Studies have shown that people who don’t get enough sleep are up to 60 percent more likely to have hypertension, and women may be at a higher risk.

“We wondered why sleep-deprived women were more prone to develop high blood pressure,” said Huan Yang, a PhD student in biological sciences with a focus on kinesiology. So she and her advisor, Jason Carter, chair of kinesiology and integrative physiology, designed an experiment to find out why.

They reasoned that the sympathetic nervous system might be involved, since it is triggered by the body’s stress response. They also identified a few prime suspects linked to gender differences: reproductive hormones, especially testosterone.

The team had thirty healthy student volunteers, fifteen men and fifteen women, stay up for twenty-four hours, tested them, and compared the results to their readings after a good night’s sleep.

Both groups showed a rise in blood pressure after being up all night, but that’s where the similarities stopped. “We found that there’s a significant difference between women and men when you look at the sympathetic nervous system,” said Yang.

Specifically, sleep deprivation lowered the men’s sympathetic nerve activity, while the women’s remained steady. This may involve gender-related differences in the body’s baroreflex, a natural response to high blood pressure that causes the heart rate to drop, Yang said. In addition, men’s testosterone levels dropped significantly, while women’s testosterone levels were relatively constant. (Yes, women have testosterone, but much less than men.)

“Men’s drop in testosterone correlated with the drop in sympathetic nerve activity,” Yang said. “This may explain why more women have higher blood pressure” when they don’t get enough sleep. In chronically sleep-deprived men, testosterone may have a dampening effect on the sympathetic nervous system, mitigating hypertension.

Yang is excited about this discovery—“This is really cool stuff!”—and she is equally proud to have addressed a lingering shortfall in medical research.

“Ours is the first study to look at the differences in sympathetic nerve activity between men and women in response to sleep deprivation,” she said. “If you don’t take sex differences into account, you may not be getting the whole story.”

Michigan Technological University is a public research university founded in 1885 in Houghton, Michigan, and is home to more than 7,000 students from 55 countries around the world. Consistently ranked among the best universities in the country for return on investment, Michigan’s flagship technological university offers more than 120 undergraduate and graduate degree programs in science and technology, engineering, computing, forestry, business and economics, health professions, humanities, mathematics, social sciences, and the arts. The rural campus is situated just miles from Lake Superior in Michigan's Upper Peninsula, offering year-round opportunities for outdoor adventure.