Fertility, Sleep and Your Body Clock

We all need our sleep to be able to function well the next day and there is growing awareness of the importance of sleep for general health. What you may not know is that how well and how long we sleep can affect male fertility, female fertility and overall reproductive health. You can learn more in The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

In this section we look at:

• The body clock and routine
• How the body clock works
• Sleep and reproductive health
• Sleep and male fertility
• Sleep, routine and eating habits
• Sleep and polycystic ovary syndrome (PCOS)
• Sleep and Diet
• Establish a good sleep routine
• Take-home message

The body clock and routine

It’s easy to underestimate how important sleep is for wellbeing but getting enough good quality sleep is crucial for us to stay healthy. Our metabolic health is significantly affected by sleep – that is the body’s ability to process the energy from food into a form of energy cells can use and to control levels of blood sugar efficiently. This is important for the general functioning of the whole body, including reproductive health and fertility. It isn’t only sleep quality that is necessary for our wellbeing, though. Our daily routine – including mealtimes and timing of exercise – controls all biological processes via what is known as the circadian clock. The circadian or body clock is in turn controlled in the brain via a set of genes and hormones that respond to environmental cues such as light, eating and temperature. Our behaviours and the responses of our brains and bodies to these cues are known as circadian rhythms.

Your body clock is designed to help you to stay awake and meet your energy requirements for living during the day and to help you sleep at night to rest and restore your body. This pattern is one example of a circadian rhythm. Individual cells also have their own circadian rhythms. The daily repair of our bodies needed to replace worn out cells also follows circadian rhythms with most tissue and cellular renewal taking place as we sleep. Studies show that wound healing is enhanced overnight, for instance, and how active genes are depends on the time of day.

How the body clock works

The circadian clock is driven by the body’s ability to respond to changes in our environment, and these changes trigger a hormonal response that then controls biological function throughout the body in a fairly logical way. Melatonin is the hormone that sends you to sleep and keeps you asleep and cortisol is the hormone that wakes us up. Melatonin production increases as daylight fades, temperature drops and energy intake stops. Our deepest sleep and lowest body temperature coincide with peak melatonin levels. As daylight breaks and temperature increases, melatonin secretion stops and cortisol production increases, and you should experience a cortisol awakening response that means you are alert when you wake up. Drowsiness or lethargy in the morning is a sign that hormone balance and circadian rhythms may be impaired and there are things you can do to improve this. The body always give us clues if we know what to look for.

Essentially, the body loves routine and this includes having a set bedtime and waking time, and eating meals at regular times each day, including snack times if healthy snacks are a usual part of your day. Having a good bedtime routine to promote sleep hygiene is also important and will help to improve any problems with the body clock.

Sleep and reproductive health

Our daily routine including mealtimes and timing of exercise can impact how our body works via the circadian clock, and vice versa. This has an impact on fertility and reproductive health. Poor-quality sleep can lead to bad eating habits, which can affect general health and fertility. Shift work, irregular sleep patterns, irregular mealtimes and disrupted sleep will all impact your circadian clock. There is growing evidence to show the circadian clock is involved in regulation of nearly every part of the female reproductive pathway including areas of the brain involved in hormone balance, the menstrual cycle and pregnancy. Disordered circadian rhythms may contribute to altered menstrual cycles, worsened period pain and, some scientists believe, changes to the follicular phase of the menstrual cycle, changes in hormone levels and increased miscarriage rates.

Sleep and male fertility

Sleep is important for male general health and fertility. Testosterone levels are affected by sleep, which in turn affects semen production. Shift work is a known risk factor for male factor infertility and studies have shown that men falling asleep after midnight have higher sperm antibodies than men who slept earlier. Poor-quality and insufficient sleep have been shown to affect sperm quality and reduce testicle size. A Danish study found that men who had late nights, woke frequently in the night or struggled to get off to sleep had a 25 per cent lower sperm count than men who experienced good-quality sleep. Shift work is also associated with poorer sperm quality.

Sleep, routine and eating habits

If you want to maintain a healthy weight, sleep and routine are key. Having enough sleep is important as short sleep duration is associated with increased risk of type 2 diabetes. Studies indicate seven to eight hours is best, and fewer than six may be harmful for overall health and fertility. However, some people do have a genetic predisposition to needing less sleep without it having an adverse effect on health or cognitive function. If you know you feel good the next day after only (say) five hours, it may be fine for you to continue like this. Be aware though that this shouldn’t mean you are overly dependent on stimulants such as coffee. If you sleep for five hours and need five cups of coffee to function throughout the day, this may not be so good for you. It’s important to be aware of your body and how you feel so you can judge what is right for you. Popular advice on waking very early with 5am starts kicking off with gym sessions or an imperative to be at your desk before dawn in order to reach your goals may sound sensible in terms of achieving things but this is no good if it damages your health. Another important personal aspect of sleep is whether you are an early bird or night owl – in other words are you naturally included to get to bed and get up early, or late – these traits are genetically determined and working against your natural body type can be damaging. So advice to get up at 5am if you are a night owl is particularly unhelpful.

Research also shows various adverse effects on metabolism following disturbed sleep. If you sleep badly, your metabolic response to a meal is impaired the next day. This can be made worse by poor food choices to compensate for the energy slump, in the same way you might eat unhealthy ‘hangover food’ following a night of heavy drinking. As a general rule, eating more calories earlier in the day helps your body use energy better and your body clock work better. Similarly, try not to eat your main meal too late – aim to eat by 7pm. Eating meals late into the evening tends to lead to a tendency to higher body weights and may also disrupt sleep, as reduced energy intake is one of the environmental cues that makes us sleepy. For many, therefore, the old maxim ‘breakfast like a king, lunch like a prince and dine like a pauper’, may be helpful. Routine for mealtimes generally is good for our body clocks, so try to have a set time for breakfast, lunch and dinner as much as possible.

Sleep and polycystic ovary syndrome (PCOS)

When it comes to fertility and weight management, sleep becomes especially important if you have PCOS (a common condition causing hormonal disturbances). Emerging evidence suggests that women with PCOS have disrupted circadian rhythms, and poor-quality sleep that is likely to exacerbate both the fertility and metabolic issues associated with the condition. A recent study in teenage girls showed a mismatch in the rhythm between melatonin and wakefulness, in other words participants with either obesity or PCOS were awake during the biological night when they should have been asleep according to a normal body clock and this led to higher testosterone levels and worsened insulin sensitivity in both groups.

Sleep and diet

A healthy diet generally supports good sleep quality but having enough protein may be particularly important. There is one particular amino acid (a sub-unit of protein) that may help with sleep – tryptophan – though more research is needed. Tryptophan is a precursor to serotonin and melatonin, both of which promote good quality sleep. The best sources of tryptophan are foods such as chicken, eggs, yoghurt, milk, oats, dates and bananas. Eating tryptophan-rich foods with carbohydrates may help them be more effective in improving sleep, so having potatoes with your chicken for dinner or rice pudding with banana before bed could be worth a try if you’re struggling with your sleep. Though the jury is still out, it is thought a glass of warm milk may be helpful for sleep but avoid adding chocolate as this acts as a stimulant. The effect of particular foods on sleep is likely to have less of an impact than overall sleep and eating routine, so focus on the fundamentals first, which we cover in detail in our Fertility and Preconception Care course.

Establish a good sleep routine

Having a sleep routine and ensuring good sleep “hygiene” can make a big difference to the quality of your sleep. This helps to optimise the production of melatonin in your body and ensure you sleep more deeply and stay asleep rather than waking in the night.

In order to develop a good sleep routine, try the following:

• Aim for eight hours’ sleep – though some have genes that make them need less.
• Have a set bedtime and waking time.
• Try to get natural daylight exposure early in the day.
• Reduce activity and mental stimulation in the two hours before bed.
• Avoid screen time that delivers high-frequency light at the blue end of the spectrum that stimulates the waking part of the brain.
• A warm bath can relax you, but beware of overheating in excessively hot baths, as this can work against melatonin (the ‘sleep hormone’) production.
• A cool, dark room is important to maximise melatonin production and allows you to fall asleep easily and stay asleep. Blackout blinds to minimise light pollution and a room at 17˚C optimise the ambient conditions for deep sleep.
• You may also want to try a daylight lamp that slowly increases light emission as an alarm to further support your circadian clock.
• Avoid caffeine after midday.
• Minimise alcohol intake and have alcohol-free days: alcohol may help you fall asleep more quickly but reduces sleep quality and increases the chances of waking in the night.
• Minimising partner disturbances such as snoring are other strategies if you know that sleep and routine are problematic for you.

You can learn more about how to optimise your sleep and understand what is right for you in our Fertility and Preconception Care course and The Fertility Book: Your Definitive Guide to Achieving a Healthy Pregnancy.

Take-home message

Getting a good night’s sleep may sound a simple thing to do but prioritising sleep can make a profound difference to your health if you’re experiencing problems. This is especially important when trying to conceive and through pregnancy. Learning to understand your body and what is right for you alongside good knowledge of the scientific evidence can help empower you to optimise your long-term health and fertility.

References

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