Men and Women: Different When it Comes to Sleep
This article in the Wall Street Journal caught my eye recently—it's a great roundup of recent research on the differences between the way men and women sleep. Gender differences in sleep are a fascinating and important area of study. We all know that men and women have different sleep tendencies—think of all those early bird/night owl partnerships out there—but we're now beginning to understand more about why gender matters when it comes to sleep.
I was particularly interested in a couple of the most recent studies, which show evidence of some fundamental biological differences between men's and women's sleep. One suggests that there are marked differences in the circadian rhythms of men and women. In this study, researchers observed the circadian cycles of 157 men and women between the ages of 18 to 74, measuring melatonin levels and body temperature in order to track the 24-hour sleep-wake cycle. Over the course of a month-long inpatient sleep period, researchers found significant differences between men and women in both the timing of their circadian clocks—which help govern sleep times and wake times—and the duration of the circadian clock itself. Among those differences:
- Women's circadian clocks are set to an earlier hour than men's, making them more inclined to fall asleep earlier and also to wake earlier. Women showed a stronger inclination for activity earlier in the day than men.
- Circadian cycles were actually shorter for women than for men, by six minutes. Even a slight difference can have significant impact on nightly sleep and on energy levels during the day. Think about a clock that runs a handful of minutes behind every day. Over time, those minutes really add up!
- Not only did women's circadian clocks generally run earlier and shorter than men's, but also many more women had internal clocks that ran a full cycle in under 24 hours.
Another recent study found that women tend to perform better than men when low on sleep, and also can rebound more quickly from mild sleep deprivation when they get restorative sleep. I was really interested in this one because it looks at the question of making up for work-week sleep deprivation with extra rest over the weekend. Women and men were asked to sleep for only six hours per night, over six consecutive nights, to approximate the typical sleep deprivation that many of us experience during a busy work week. The participants then spent two nights "catching up" on their rest with extended overnight sleep. Researchers found that women scored higher on performance tests during the period of low sleep, and that their performance improved more than men's after two nights of extended sleep. (Take note: Neither men nor women in the study were able to truly "catch up" on their sleep over the two nights. Both fell short, but women simply came closer than men.) We know that women spend more time than men do in deep, slow-wave sleep stages over the course of a night. Time spent in deep sleep is restorative and memory boosting, which likely explains the advantage women have in performing under low-sleep conditions.
Women may reap real benefits from deeper sleep, but there is also evidence that they are in other ways more vulnerable than men to sleep disorders, and to the health risks associated with lack of sleep.
The biological phases of a woman's life—menstruation, pregnancy, menopause—and the hormonal shifts that accompany them make women more likely to experience disruptions to their sleep. Women in general are more susceptible than men to sleep disorders such as insomnia. Because of their propensity for deep sleep during the first part of their lives, women may receive protective benefits early on. But particularly after the age of 40, women's sleep often deteriorates.
- Research suggests women have a different relationship with sleep when it comes to illness. One study showed that women who got less than 8 hours of sleep demonstrated an elevated risk for heart problems. Men in the study who got the same amount of sleep also saw increased risk, but the increase was not as significant as it was for women. The results of a recent study on cancer and sleep found that women were significantly more likely than men to suffer from insomnia while undergoing cancer treatment.
I'd like to see even more research that sets out to explore differences in the ways men and women experience sleep. The more we understand about how gender influences sleep, the better we'll be able to develop targeted, effective remedies for sleep problems for both men and women.
Michael J. Breus, PhD
The Sleep DoctorTM
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