Is your wife 'too tired' for sex? Don't worry - it's probably just her faster circadian rhythm
Last updated at 9:13 AM on 6th May 2011
It turns out women who say they are just too tired for sex may not be making excuses after all.
According to a Harvard study, they run on a different biological sleep clock to men - and need to go to bed earlier because of it.
Women's circadian rhythms run six minutes faster than men's, making them much more likely to be early birds rather than night owls.
Frustrated: Women may be too tired for sex in the evenings because their circadian rhythms are faster than men's, so they need to go to sleep earlier
They report insomnia around 50 per cent more frequently than their male counterparts, especially the early morning kind, where they wake up and cannot get back to sleep.
It helps explain why women are often up with the lark, while their partners stay slumbering long into the morning.
But women can end up being chronically sleep-deprived because they try to fight against their faster sleep cycles and fit too much into the evenings, before being woken up too early by the light.
According to the study, for many women their natural instinct is to go to bed early - so sex can be the last thing on their minds in the evening.
Mismatched rhythms: According to the study, women have a faster sleep clock than men, so often wake up much earlier - making them tired later
The findings were released by researchers at the Harvard-affiliated Brigham and Women's Hospital.
It's based on results produced by 157 people who spent eight weeks in a windowless sleep lab in Boston.
They were isolated from all cues about the time in the outside world, allowing their body clocks to go back to natural circadian rhythms.
Jeanne Duffy, one of the study's authors, told NPR: 'What we found was that the cycle length of the biological clock in women was shorter on average than it was in men.
'The average difference was about six minutes.'
New findings: Dr Jeanne Duffy, left, wrote the study with Charles Czeisler, right
Although she acknowledged it didn't seem like much, she compared it a watch running too fast.
WHAT ARE CIRCADIAN RHYTHMS?
Circadian rhythms describe regular changes in mental and physical characteristics which occur throughout the day.
They are controlled by the body's biological clock, known as the suprachiasmatic nucleus (SCN).
This is controlled by light which hits the retina and then travels along the optic nerve to the SCN.
The SCN then sends signals to other parts of the brain, including the pineal gland, which controls the production of melatonin.
When darkness falls, a signal travels to the pineal gland so it produces more melatonin, making you feel sleepy.
If deprived of external cues, most people's biological clocks work on a 25-hour clock.
But sunlight resets the SCN, so we follow its 24-hour cycle instead.
Flying from one time zone to another disrupts circadian rhythms, causing jet lag because your body clock takes several sleep cycles to get used to the new time.
Shift workers can experience similar symptoms to jet lag, because their schedules are so different to powerful sleep-regulating cues like sunlight.
Many people who are blind have life-long sleep problems because their circadian rhythms follow an innate cycle, as their retinas cannot detect light.
Without resetting it, it would get more and more out-of-sync with the 24-hour clock we live by, because we follow the sun rather than our innate 25-hour cycle.
That six-minute variation can be further amplified by factors such as when light first hits the eye.
Some women - more than one in three - have inner clocks which run particularly fast, so they can complete a daily cycle in less than 24 hours.
It is particularly important for these women to reset their internal clocks.
Dr Duffy said: 'If your cycle length is shorter than 24 hours, you need evening light to keep you synchronised.'
She suggested wearing sleep masks or installing blackout shades to keep morning light to a minimum.
Men who tend to wake up later should avoid lots of evening light, and make sure they get plenty of bright light in the morning.
According to Charles Czeisler, a professor of sleep medicine and a physician at Harvard Medical School, millions of women are fighting against their faster circadian rhythms every day.
He told NPR: 'I definitely think that's happening out there. I think many women are chronically sleep-deprived because of their work obligations.
But he added many women don't see their early bird tendencies as a problem.
He said: 'There are many women who really enjoy the fact that they can get up at 4 or 5 o'clock in the morning.
'They have peace and quiet. Before the rest of the world wakes up, they can get an extraordinary amount done - and they wouldn't trade it for the world.'
Read more: http://www.dailymail.co.uk
No comments:
Post a Comment