A poor night's sleep causes greater psychological distress and more elevated health risks in women than men, a new study from the United States suggests.

A researcher from the Duke University Medical Center, in North Carolina, found that when he compared women and men with similar poor sleep patterns, women showed dramatically higher levels of distress and of biomarkers associated with the risk of heart disease and Type 2 diabetes.

"The study suggests that poor sleep — measured by the total amount of sleep, the degree of awakening during the night and, most importantly, how long it takes to get to sleep — may have more serious health consequences for women than for men," said author Edward Suarez, an associate professor at the university's department of psychiatry and behavioural sciences, in a release.

"In women but not men, poor sleep and sleep-related symptoms are associated by a mosaic of plasma biomarkers and psychosocial distress associated with increased risk of Type 2 diabetes, CVD [cardiovascular disease] and other chronic medical conditions," he wrote in the study, published last week in the online edition of the journal Brain, Behavior and Immunity. 

The study compares the responses of 210 healthy, middle-aged men and women on their quality of sleep during one month and on the levels of biomarkers associated with increased risk of heart disease and diabetes — such as insulin and glucose — in their blood samples.

Roughly 40 per cent of the participants, both men and women, were classified as poor sleepers, that is, they had problems falling asleep, took 30 minutes or more to fall asleep or woke frequently during the night.

But, Suarez found, despite similar sleep profiles, the women had dramatically higher risk profiles.

"We found that for women, poor sleep is strongly associated with high levels of psychological distress, and greater feelings of hostility, depression and anger. In contrast, these feelings were not associated with the same degree of sleep disruption in men," he said.

Additionally, he found that women who slept badly had higher levels of biomarkers for health risks. For example, 33 per cent of women considered poor sleepers had high levels of C-reactive protein, a measure of inflammation associated with increased heart disease risk. No such increase was measured among the men.

"This is the first empirical evidence that supports what we have observed about the role of gender and its effects upon sleep and health," Suarez said. 

Time spent on the way to dreamland more important than quality

The study also found that the length of time it took the volunteers to fall asleep was tied more closely to the elevated health risks than overall quality of sleep.

"Women who reported taking half an hour or more to fall asleep showed the worst risk profile," Suarez said.

Suarez said he's planning further studies into the relationship between gender differences, sleep and health risks.

He said the gender differences may be due to a variation on some substances that occur naturally in the body, such as the amino acid tryptophan, the neurotransmitter serotonin and the neurohormone melatonin.

"Good sleep is related to good health," Suarez said. "More research needs to be done to define gender-linked responses to poor sleep, including the role that sex hormones play over a lifetime and how sleep needs and responses change from childhood to maturity."