From a meta-analysis, researchers from the University of Pennsylvania have found that men and women tend to have different circadian rhythms- the internal process that regulates the sleep-wake cycle.
While the body is regulated by many rhythms, the circadian rhythm is perhaps the most well known as it affects our lives on an observable day-to-day basis. Involved in metabolism, it is responsible for why we get tired at certain hours and not others- as well as when we fall asleep and when we awaken.
In the current study, the researchers analyzed papers on investigating the circadian rhythm involving over 53,000 people. As such, they found some key differences in these rhythms according to gender. In particular, they noticed that women tend to be morning people, whereas men are more likely to be 'night' people.
They noted that women also tend to be more resilient to disruptions in their sleep-wake cycle, more active in the day, and less energetic at night- a pattern that matches that of children. Women also tend to spend more time sleeping than men, including more time in slow-wave deep sleep.
On the other hand, men tend to be more alert than women while sleeping, and also tend to take more naps in the afternoon.
While the researchers do not know exactly what may account for these variations, they say that the women's maternal role may play a part given traditional settings involving child-rearing. In this scenario, they say it may have made more sense for women to have a circadian rhythm more in tune with their offspring.
The researchers also noted previous work drawing a link between circadian rhythm in women and their estrous cycles. They, however, made no mention as to what may influence men's' circadian rhythms to skew more towards night hours.