A new review of research has examined the key differences in the sleep patterns of women and men, the fluctuations in their body clocks and the impact on their metabolism. The study, published in the journal Sleep Medicine Reviews, highlights the crucial role that gender plays in understanding these factors and suggests that a person’s biological sex should be taken into account when treating sleep, circadian rhythms and metabolic disorders.

Sleep-related Eating Disorder Much More Common in Women, Men More Affected by Obstructive Sleep Apnea

The review found that women rate their sleep quality lower than men and report greater fluctuations in their sleep quality related to changes during the menstrual cycle. Poorer sleep quality is associated with anxiety and depressive disorders, which are twice as common in women as in men. Women are also more likely to be diagnosed with insomnia than men, according to the researchers, although the reasons for this are not entirely clear. Recognizing and understanding gender differences in sleep and circadian rhythms is crucial for tailoring approaches and treatment strategies for sleep disorders and related mental illnesses.

The study authors also found that women are 25 to 50 percent more likely to develop restless legs syndrome and up to four times more likely to have a sleep-related eating disorder, in which sufferers eat repeatedly during the night. Men, on the other hand, are three times more likely to suffer from obstructive sleep apnea (OSA). OSA manifests itself differently in women and men, which could explain this disparity. OSA is associated with an increased risk of heart failure in women, but not in men.

Sleep laboratory studies have shown that women sleep more than men, and spend about 8 minutes longer in non-REM (Rapid Eye Movement) sleep, a time when brain activity is slowed. While the time we spend in NREM sleep decreases with age, this decrease is more pronounced in older men. Women also enter REM sleep, which is characterized by high brain activity and vivid dreams, earlier than men.

Different Circadian Rhythms

The team of female researchers from the University of Southampton in the United Kingdom and Stanford University and Harvard University in the United States found that there are also differences in circadian rhythms between the sexes.

They found that melatonin, a hormone responsible for timing 24-hour rhythms and sleep, is released earlier in women than in men. Core body temperature, which is highest before sleep and lowest a few hours before waking, follows a similar pattern, peaking earlier in women than in men. In line with these findings, other studies suggest that women’s intrinsic circadian periods are about six minutes shorter than men’s.

According to the researchers, this difference may be small, but it is significant. The discrepancy between the central body clock and the sleep-wake cycle is about five times greater in women than in men. Over the course of days, weeks and months, this difference can lead to a noticeable discrepancy between the internal clock and external cues such as light and darkness.

Circadian rhythm disruptions have been linked to various health problems, including sleep disorders, mood swings and impaired cognitive function. Even small differences in circadian periods can have a significant impact on overall health and well-being. Men tend to be later chronotypes and go to bed and wake up later than women. This can lead to social jet lag, where their circadian rhythm does not align with social demands such as work. They also have less consistent rest and activity schedules than women in daily life.

Increased Risk of Type 2 Diabetes in Both Sexes

The research team also investigated whether the global increase in obesity could be partly linked to people not getting enough sleep – in the United States, 30 percent of 30-64 year olds sleep less than six hours a night, and in Europe, a similar number. There were large differences between the brains of women and men who responded to images of food after sleep deprivation. Brain networks associated with cognitive (decision-making) and affective (emotional) processes were twice as active in women as in men. In another study, the limbic region (involved in processing emotions, memory formation and behavior regulation) was found to be 1.5 times more activated in women than in men in response to images of sweet foods. Despite this difference in brain activity, men tend to eat more than women when they are sleep deprived. Another study found that more fragmented sleep, a longer time to fall asleep and a longer time spent in bed trying to fall asleep were only associated with more hunger in men.

Both women and men who work night shifts have a higher risk of developing type 2 diabetes, with this risk being higher in men. Sixty-six percent of night shift workers suffered from emotional eating, and according to another study, they are about 1.5 times more likely to be overweight or obese than women who work the day shift.

More Personalized Health Care

The researchers also found new insights into how women and men respond differently to treatments for sleep and circadian disorders. For example, weight loss was more successful in treating women with OSA than men, while women prescribed zolpidem (a medication for insomnia) may need a lower dose than men to avoid persistent sleepiness the next morning.

Most sleep and circadian interventions are an emerging field with limited research on sex differences. As we learn more about how women and men sleep, the differences in their 24-hour rhythms, and how these affect their metabolism, we can move toward more precise and individualized health care that increases the likelihood of positive outcomes.