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Sleep- why is it so important? Immune system function, weight loss, blood pressure and more...

Updated: Mar 9, 2021

Recently, I've had a number of patients who've told me they survive on 4/5/6 hours sleep a night when I go through their history or seem to have enough hours sleep but wake up feeling very tired still. This may not only be due to the time they actually go up to bed and wake up for work but also due to how much they wake up throughout the night or the quality of their sleep.

The research into how and why we sleep is growing, with very interesting findings coming out on why sleep is important not only for energy levels but even for optimal immune system function and even weight loss.

Recently, I read a book by a neuroscientist, Matthew Walker ('Why we sleep'). Here's the main take home points...

How do we sleep? Sleep cycles...

The sleep cycle is divided into REM (rapid eye movement) sleep and NREM (non rapid eye movement sleep). The NREM sleep is divided into 4 stages, ranging from lighter to deeper sleep. This happens in cycles between NREM and REM through the night, every 90 minutes, where NREM sleep begins.

In the first half of the night, most of our sleep cycle is made up of deeper NREM sleep, while towards the end it is made up of more REM sleep (which starts at 10 minutes and increases to 1 hour at the end of sleep).

When we are fully awake our brainwaves are fast and erratic. Stages 3 and 4 of NREM sleep are slow wave sleep and are regular. When we are back in REM sleep our waves return to how we are when we are awake. During REM sleep however, our muscles are completely paralyzed with no tone in the voluntary muscles of your body (although our involuntary muscles continue obviously to control breathing and keep us alive). So although our brain waves are very similar in REM sleep and being awake, this paralysis of muscle tone is how scientists differentiate between being awake vs in REM sleep. This paralysis prevents us from acting out of dream experience (although for some people this isn’t always the case). Rapid eye movement is also, obviously, a key distinguishing factor.

Why do we sleep?

Both parts of sleep are very important for us:

NREM sleep is important in weeding out and removing unnecessary neural connections/memories while storing the raw ingredients of new facts and skills.

REM sleep helps us strengthen certain connections, integrating these raw skills with past experience and therefore helping with problem solving and innovative insights. Recent MRI studies have even shown parts of the brain to be 30% more active when we are asleep compared to when we are awake!

Interesting facts:

  • 7-9 hours is optimal.

  • 5 hours of sleep a night can make you 4x more likely to get a cold than getting 8 hours a night.

  • Getting even 6 hours of sleep per night for 1 week can make healthy individual’s blood sugar levels rise. It can cause an increase in the genes responsible for cardiovascular disease, stress and cancer, decrease heart rate variability and negatively impact the gut microbiome.

  • One large study of 1.7 million people showed a 20% increase/decrease in heart attacks when the clocks go forward/back.

  • Even one night of 4 hours sleep can cause a 70% decrease in natural killer cells which are important for our immune system response to fight things like infections and cancer.

  • Deep sleep decreases heart rate, blood pressure and cortisol (which is our stress hormone).

  • When we're sleep deprived there is a 60% increased reactivity of the amygdala, which is in charge of our emotional reactions.

  • Decreased sleep causes decreases in Leptin, a hormone that tells us we’re full, and increases in Ghrelin, a hormone that increases hunger. Studies have shown we consume 200-300 extra calories a day when sleep deprived.

  • Although we often think of alcohol as a good 'night cap' to help us sleep, alcohol actually has been shown to decrease our REM sleep.

  • Caffeine has a half life of around 6 hours and a quarter life of 12 hours, so drinking your last cup after midday could still affect your sleep!

So it's all well and good knowing how important sleep is and why we need enough but what about if we struggle to get off to sleep or wake up frequently in the night? Obviously there can be a lot of causes for this from musculoskeletal pain to overthinking or sometimes we just have no idea why it happens!

If this is the case, the first thing I'd try are these sleep hygiene tips:

  1. Go to bed and wake up at roughly the same time each day. There is some thought that there's such thing as 'social jet lag' which can occur at weekends when we've changed our sleep routine!

  2. Keep the room cool, at around 18 degrees. Having a hot shower/bath or drinking a hot herbal tea before bed can also help with this by physiologically causing our body temperature to drop when we get out of the shower or sweat.

  3. Limit blue light before bed (laptops/phones/ipads/TVs) and decrease bright lights in the house as they can affect melatonin production (the hormone that helps us sleep). Top Tip: Turn on 'Night Shift' mode on your smartphone- under Settings, Display and Brightness and turn down the brightness on your phone. Try not to use a these devices roughly 1 hour before bed. Use candles in the house in the evenings or buy some Blue light blocking glasses.

  4. Avoid caffeine, especially after midday (this can include fizzy drinks like colas, certain teas and chocolate, as well as coffee). As stated above, caffeine can stay in our system for much longer than we'd think. Why not try going to decaf drinks and see if it helps?

  5. If you've been awake for over 20 minutes, or start to feel anxious or worried, get up and try reading a book in another room. Only return to bed when you're sleepy.

  6. Exercise is great and does help sleep, but not if it's too late in the day. Try not to exercise within 2-3 hours of going to bed.

  7. Avoid alcohol before bed.

  8. Nicotine can also cause us to have less deep sleep and wake up early in the morning due to nicotine withdrawal, so stopping smoking could also help your sleep.

  9. Avoid large meals late in the evening as it may cause indigestion. Avoid drinking too much fluid before bed as it may cause you to wake up more to urinate.

  10. Naps can be beneficial but try not to take them after 3pm.

  11. Relax before bed- try reading, listening to music or some mindfulness.

  12. Expose yourself to sunlight for at least 30 minutes each day. Wake up to bright light/sunlight if possible or even just sit out in the garden for 10 minutes in the morning when it's light.

So why not see what tips you could put into practice to help your sleep?

For extra information:

Have a read of Matthew Walker's book 'Why we sleep'.

Listen to the Feel Better Live More podcast he's been on with Dr Rangan Chatterjee.

For parents struggling to get their kids to sleep well...

For a free consultation on whether she may be able to help you with an individual program.

For helps with Insomnia and sleep issues, through the NHS or privately, Sleep Station is a organisation that may be worth looking in to:

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