Why mothers more quickly get up early?

In each family, usually the mother or daughter woke up earlier than his father or son. Why is that?

There are many differences between the male body and female. And a recent study found that women tend to have shorter sleep cycles than men.

This makes women usually went to bed early and wake up in the morning too early. This is also causing more and more women are experiencing insomnia and seasonal depression.

"This has implications for how easily they (women) could fall asleep and how well (quality) they can sleep. It can change and contribute to differences between individuals to go to bed and wake up in the morning," said Harvard researcher Jeanne Duffy Medical School, as reported by LiveScience.

The researchers found that on average in the 24-hour sleep-wake cycle of women (called a circadian rhythm), approximately six minutes shorter than men, but in reality this is actually sleep and wake up early is tantamount to about 30 minutes early.

"These findings could be related to differences in levels of estrogen," said Duffy.

This could mean that the hormone levels can alter circadian rhythms, although the evidence on female pre-and post-menopausal showed that the sleep cycle associated with hormone exposure during development (hormones), not because the level of maturity.

"Finding out what that control our biological clock is one of the most important question in the chronology of human research now," said Alfred Lewy, Oregon Health and Science University in Portland, who was not involved in this research.

In this study, the research team led by Duffy and advisor to Charles Czeisler, studying the sleep cycles of 52 women and 105 men for two to six weeks in the laboratory.

They examined two indicators of circadian rhythms, the core body temperature of participants and level of the hormone melatonin (which plays a role in regulating sleep-wake cycle). Meanwhile, participants follow an extreme schedule (after a sleep cycle, activities are spread 20 or 28 hours a day, not the normal 24 hours) in the dim room.

The environment allows researchers to measure the natural circadian rhythm of the individual, which typically reset every day by exposure to natural light.

Without external cues, the body back in a natural cycle that is sometimes longer or shorter than 24 hours.

The result, in this study about 35 percent of women have a shorter circadian rhythms of 24 hours, compared with 14 percent of men.

This distinction is important for people with seasonal depression, treated with light therapy to reset the circadian rhythm. If you have a cycle shorter than 24 hours, people need to light the night to sync up, and if it is more than 24 hours, people need a light in the morning.

This research was published online on May 2 in the journal Proceedings of the National Academy of Sciences.