Women and men have different sleeping patterns and report different sleep problems. The science behind these differences could go a long way toward explaining gender differences in quality of sleep and overall health.
We all know that getting enough sleep, and the quality of that sleep, greatly affects our wellbeing. But the differences between the sexes in how we sleep may surprise you. On average, women fall asleep faster and sleep longer than men, and they also have more deep sleep and fewer interruptions.
Yet women are 50 percent more likely to have insomnia than men, and life changes such as pregnancy and menopause create huge disruptions in sleep cycles. More men report being satisfied with the amount and quality of their sleep. So how do these differences all break down, and what does it mean for overall health?
Different Body Clocks
Men and women have different circadian rhythms, new research has found. Jeanne Duffy, associate professor of medicine at Harvard Medical School, looked at 157 healthy people, mixed between genders, over a 10-year period. The average circadian period for a man was 24 hours and 11 minutes - six minutes longer than the average woman's circadian period.
While six minutes may not sound like a lot, Duffy says the difference is significant. The longer body clock for men means that they are predisposed to want to go to bed later and get up later. Twice as many women had a body clock shorter than 24 hours, and tended to prefer going to bed earlier and getting up earlier, and a greater preference for morning activities. Past research shows that women sleep 19 minutes longer than men, on average.
As Duffy's study suggests, these different sleeping patterns could cause problems in male/female living partnerships. Most people regularly sleep with a partner, and gender differences in body clock could cause insomnia for one person whose sleep may disrupt the other. Duffy adds that getting more sleep may give women the advantage in better health and longer life spans.
Daniel J. Buysse, a professor at the University of Pittsburgh's Sleep Medicine Institute, conducted a study in 2010 that looked at the effect that marriage and cohabitation had on sleep. He found that in women particularly, those who were partnered had better sleep quality than those who were not.
Sleep Apnea: Not Just a Male Problem
Perhaps one reason that men are more satisfied with their sleep quality than women is due to the fact that women are consistently under-diagnosed for obstructive sleep apnea, a potentially dangerous condition where sleep is constantly interrupted due to abnormal breathing pauses.
According to the National Institutes of Health (NIH), 75% of all sleep research is done on men. These findings are typically presented as "normal" even though there are important sleep-related physiological differences in women.
Doctors' preconceived ideas of the typical sleep apnea patient, namely middle-aged overweight men, likely influence the oversight of women, said Grace W. Pien, MD, in an NIH interview with Dr. Barbara Phillips. Pien is an assistant professor at the University of Pennsylvania School of Medicine. "They may not think of this diagnosis when the patient is female. Second, women may present with slightly different symptoms than the 'classic' symptoms…instead, women may present with fatigue, insomnia, morning headaches, mood disturbances or other symptoms," Pien said.
Sleep apnea is a significant risk factor for cardiovascular disease; there is a prevalence of about 30-70 percent of hypertension in sleep apnea patients. This prevalence is similar in men and women, until you take the body mass index into consideration. Then, gender differences emerge - men who are obese have twice the risk of hypertension than obese women.
Women's Reproductive Changes Affect Sleep
A woman's risk for sleep apnea increases when she goes through menopause, Pien says. "Post-menopausal women are up to three times more likely to have OSA compared to premenopausal women." Sleep disorders are also more common during pregnancy.
According to the National Sleep Foundation's 1998 Women and Sleep poll, 78% of women report more disturbed sleep during pregnancy than at other times. Changing hormone levels are one reason for this, as well as nausea and other pregnancy-related discomforts, and the possible anxiety that comes from impending childbirth and motherhood. The National Sleep Foundation also reports that several sleep disorders can be caused or made worse by pregnancy.
In a study of over 600 pregnant women, more than one-fourth reported symptoms of restless legs syndrome, and 30-50 percent experienced heartburn. Frequent nighttime urination also keeps pregnant women up at night. The NIH even questions the effects of the regular menstrual cycle on sleep.
Quality vs. Quantity
Researchers are a bit puzzled by the reasons why women complain more about the quality of their sleep, even though they get more sleep on average than men. Buysse thinks that this is due to interrupted sleep; fragmented sleep is less restful than solid deep sleep, even if the amount is greater. Buysse adds that women are more likely to suffer from depression, which can lead to sleep disorders.
Research at the University of Michigan showed that working mothers are two-and-a-half times more likely to interrupt their sleep to take care of others. In the first national study of its kind to look at the gender differences in parents getting up at night to tend their children, such interruptions averaged 44 minutes for mothers, but only 30 minutes for dads.
Sarah Burgard led the study, analyzing time diaries from about 20,000 working parents between 2003 and 2007. She found that the gender gap in sleep interruption was greatest during child bearing and rearing years, and that interrupted sleep is a burden disproportionately borne by women.
The differences were greatest among dual-career couples with a child under one year old. In those cases, 32 percent of women reported getting up at night to care for the baby, compared to only 11 percent of men. The disproportion declined as the age of children increased.
As Burgard points out, getting a few minutes more total sleep per night may not compensate for the greater sleep interruptions that women deal with. "Sleep interruption may represent an under-recognized 'motherhood penalty' that influences life chances and well-being," she says.