Why you should always ARGUE over breakfast (but never before bed)
Why you should always ARGUE over breakfast (but never before bed) – Top Oxford professor reveals how to harness your body clock so you can have a happier marriage
- Women tend to get up earlier and experience their best thought processing earlier in the day, and become ready for sleep earlier in the evening than men
- Professor Russell Foster says this sexual difference in body clock type has been linked to the sex hormones
- The thinking is that if you can accommodate the sleeping habits of your partner, you will have enough emotional flexibility to deal with all the other difficulties
Men are from Mars, women are from Venus — or so one well-known book title would have it. Now I’m no relationship guru, but certainly when it comes to the way our body clocks work, men and women are very different — and by appreciating and respecting each other’s differences, the path to true love could be smoothed.
Today, in the third and last part of this series, I am going to show you how to harness your body clock so you can have a happier marriage, improve your chances of conceiving and understand yourself — and your partner — better.
One of the key differences is the fact that our chronotypes — whether we are morning or evening people, ‘larks’ or ‘owls’ — can be greatly influenced by our sex, and that if you are in a relationship, whether or not your chronotypes, and therefore body clocks, ‘match’ may have a bearing on how happy the relationship is.
We know that chronotypes differ between males and females thanks to studies first on rodents, and then humans. One study, by Canadian researchers in 2016, compared the body clocks, or circadian rhythms, in men and women’s body temperature, sleep/wake cycle and alertness — all of these rhythms occurred earlier in women, meaning women tend to get up earlier, experience their best thought processing earlier in the day, and become ready for sleep earlier in the evening than men (a surprise, perhaps, to many women watching their partners snooze on the sofa).
Professor Russell Foster says one study found women tend to get up earlier, experience their best thought processing earlier in the day, and become ready for sleep earlier in the evening than men
Separately, data from the American Time Use Survey (an ongoing study finding out the amount of time people spend doing various activities) showed that men are typically later chronotypes, with the greatest differences observed in teenagers and young adults. After the age of 40, men and women’s chronotypes become slightly more aligned. These findings have also been confirmed in a study in 2020 of 53,000 men and women from the U.S.
This sexual difference in body clock type has been linked, perhaps unsurprisingly, to the sex hormones — oestrogen and testosterone — though quite how and why these hormones influence our clocks is still unclear. But the bottom line is that women will tend to want to get up earlier in the morning than men — so even if we don’t know why, we can look at how it affects a couple’s relationship.
One recent study suggested that women typically report being happier and most relaxed when she and her partner share the same chronotype, going to sleep and waking up together.
However, such relationships are fairly rare, considering most women skew to an earlier chronotype than men. The same study suggested that there was no link between frequency of sexual intercourse and chronotype — interesting, as logic would suggest that different bedtimes might interfere with sex life.
Yet many ‘mismatched’ couples do, of course, remain together. Till Roenneberg, a scientist based in Munich, who has done research in this area, concludes: ‘Many people think that the best relationship is the one where the two chronotypes are the same, but this is wrong.’
The thinking is that if you can accommodate the sleeping habits of your partner, you will have enough emotional flexibility to deal with all the other difficulties that life throws at the partnership. So it reflects perhaps your flexibility and your attitude to work towards being accepting of your partner.
There are also a number of potential advantages to having a different chronotype to your partner — not least that parents with different chronotypes, such as a lark paired with an owl, could certainly find their differences helpful when rearing a child.
WHY JET-SETTERS RISK THEIR FERTILITY
Synchronisation of these complex systems is essential for successful reproduction, which is why disrupted body clocks in women, as seen in night-shift workers or jet-setters, is associated with irregular and longer menstrual cycles, reduced fertility and a higher risk of miscarriage
Even the initial act of conception is a complex business, as anyone who has struggled to start a family will appreciate. It’s more difficult than school sex education lessons would have you believe and is another astonishing example of the importance of getting the correct materials in the right place, in the right amount, at the right time.
I assume that the basic facts of life will be well known to you. So I will skip straight into the glories of precisely when to have sex to maximise your chances of conceiving.
The timing of ovulation (when the ovaries release a mature egg, ripe for fertilisation by a sperm) involves complex interactions between the brain, pituitary gland, ovaries and body clocks in these tissues.
The activity of these peripheral clocks is coordinated by the ‘master clock’ located in the suprachiasmatic nuclei (SCN) area in the brain. (As a reminder, the master clock needs to be reset daily, with regular exposure to light along with regular eating and sleeping patterns.)
Synchronisation of these complex systems is essential for successful reproduction, which is why disrupted body clocks in women, as seen in night-shift workers or jet-setters, is associated with irregular and longer menstrual cycles, reduced fertility and a higher risk of miscarriage.
So it is important to stress that while the effects of shift work on fertility vary greatly between individuals, shift work, jet lag and poor sleep are potential risk factors for fertility in some women.
Many clinical practitioners advise women not to undertake shift work or multiple long-haul flights if undergoing IVF, and if you are trying to conceive naturally, it may be worth considering doing the same.
WE CAN’T RESIST A DEEP VOICE BEFORE OVULATION
We know that heterosexual women experience greater sexual desire and are more attracted to strong male features such as deep voices during their peak fertility in the days before ovulation
Following ovulation, sperm are capable of fertilising an egg, with pregnancy most likely when intercourse occurs around three days before ovulation.
It is thought this gives the sperm enough time to travel from the cervix to the fallopian tube, where it meets the newly released egg (the egg, unfertilised, only has a lifespan of 12 to 24 hours). Now you can see how incredibly narrow the window for fertilisation really is.
A lot of biological effort has gone into producing a nicely-timed ovulation, and so the question arises: ‘Is sex similarly timed to maximise fertilisation?’ With such a tiny window for success, it would be surprising if our biology did not, in some way, prepare us for action.
DID YOU KNOW?
Men take longer to adjust to jet lag than women, and it’s testosterone that’s key: it has been linked to a reduced sensitivity to light for resetting the body clock. In studies on mice, females adapted to a new ‘time zone’ after six days, while males took ten. If we are like mice (we usually are), this means men should get plenty of natural light in the new time zone.
Indeed, there is good evidence that human sexual behaviour does change around the time of peak fertility. The most obvious body clock cycle that’s holding sway being the (roughly) 28- day menstrual cycle. We know that heterosexual women experience greater sexual desire and are more attracted to strong male features such as deep voices during their peak fertility in the days before ovulation.
Heterosexual men, for their part, can even ‘sense’ a woman’s fertility in the days leading up to her releasing an egg. They seem to be affected by odorants secreted by women called ‘copulins’. Copulins increase in concentration during the phase of the menstrual cycle leading up to ovulation, and decrease in concentration after an egg is released. Studies show that men exposed to copulins produce more testosterone, become less discriminating about a woman’s looks and behave more assertively.
The effects are not large but they are significant. Together with whatever methods to improve your chances you may already be using — such as home testing for ovulation — it is worth bearing in mind the importance of sex in the days before your hormonal peak shows up on such tests.
HAVE SEX FIRST THING IN THE MORNING
The thinking is that if you can accommodate the sleeping habits of your partner, you will have enough emotional flexibility to deal with all the other difficulties that life throws at the partnership
There is a circadian rhythm of testosterone release from the testes of men, rising from about midnight and peaking in the morning before they wake, with levels of testosterone in young men about 25 to 50 per cent higher at this time than for the rest of the day. In addition, a study examining more than 12,000 semen samples from 7,068 men found that those collected before 7.30am showed the highest levels in sperm concentration and healthy sperm motility, size and shape.
While it’s unclear why sperm production should peak in the early morning, these findings suggest that men may increase their chances of fertilising an egg by having sex first thing in the morning when their sperm is at its most top-notch.
WHY BABIES ARE BORN IN THE EARLY HOURS
The hormone melatonin is released by the pineal gland at night and could drive a nocturnal signal for the production of other hormones that increase the contractions of the uterus, such as oxytocin
Around the world, the peak hours for natural childbirth fall between 1am and 7am, peaking at around 4am to 5am.
Clearly, babies can be born at any time of the day or night, but this clustering of births in the early morning strongly implicates some level of circadian rhythm is involved.
So what might be the evolutionary advantage of this timing? Suggestions include that birth overnight would have been useful for mothers in a hunter gatherer society, because the group would be reunited at night, providing protection and social support, which would not be available during the day when the group was dispersed to forage. In addition, there would also be reduced predator activity and reduced heat in the middle of the night.
So the peak in human births during the early-morning hours could be a vestige of our evolutionary history, when survival was increased if birth occurred at this time. These evolutionary explanations have been coupled to key changes in hormone levels. The hormone melatonin is released by the pineal gland at night and could drive a nocturnal signal for the production of other hormones that increase the contractions of the uterus, such as oxytocin.
Support for this idea comes from studies which show melatonin levels are higher in late pregnancy and that melatonin may increase the sensitivity of the uterus to oxytocin, which in turn stimulates powerful contractions that move the baby down and out of the birth canal.
HOW TO DIVORCE PROOF YOUR MARRIAGE
Multiple studies have shown that divorce rates are higher for night-shift workers. One U.S. study found that among men working night shifts who had children, separation or divorce was six times more likely in the first five years of marriage than if they were day workers.
The same kind of trouble these couples face can also be faced in couples where each partner is of an extremely different chronotype.
But whether you are a lark and an owl heading to bed several hours apart, or whether one of you works nights and the other is on day shifts, my key bit of advice is to avoid talking about problems late at night when you are in bed. Discuss tough topics after breakfast, not dinner.
I appreciate that the evening may be the only time to talk to your partner about pressing matters — but it is reallyimportant to avoid any stressful topics immediately before bed.
That’s partly because you will both be be rattier — our mood begins to elevate in the morning, peaks during the late morning and early afternoon and plummets towards bedtime. Lots of hormones rise in the morning anticipating activity, but which are responsible for these mood changes remains uncertain.
We know that the stress hormones cortisol and adrenaline are released in response to an angsty conversation. Higher levels of these hormones before bed will increase alertness and this will act to delay sleep. Note that tiredness drives irritability, impulsivity and a lack of empathy.
Part of the reason for this is again because of the stress hormones. When tired and fighting the urge to sleep, cortisol and adrenaline are released. They keep us awake but make us more irritable, impulsive and less understanding of others. Knowing this, think carefully before speaking unless you are both fully rested.
- Adapted from Life Time: The New Science Of The Body Clock And How It Can Revolutionise Your Sleep And Health by Russell Foster is published by Penguin Life on May 19 at £16.99. © Russell Foster 2022. To order a copy for £15.29 (offer valid until May 21, 2022; UK P&P free on orders over £20), visit mailshop.co.uk/books or call 020 3176 2937.
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