Have you ever had a tough decision to make and someone told you to sleep on it?

Well, they may have been on to something.

To understand the benefits of sleep, you just have to experience not getting enough. Inadequate sleep can mean your work performance is poor, your physical health struggles, you’re more likely to catch a cold, and you become overwhelmed at just about anything (including what to have for dinner). There’s a reason we’re meant to spend a third of our lives asleep.

Why do we need sleep?

Sleep gives our brains and bodies the chance to recover and rebalance each day.

When we’re awake, our nerve impulses and neural connections work hard to keep up with our daily demands^[1]. During the day, the synapses in our brain – the junction between nerve cells – are under constant stimulation, which is essential for our memory and learning^[3]. Sleep allows our neural networks to slow down and go back to a baseline, so our brains don’t get overloaded^[3]. This process, known as potentiation, stops our minds from getting overwhelmed and enables us to wake up feeling refreshed and ready for the day ahead^[3]. Microscopic image of our synapses have shown that they expand during daytime stimulation and shrink with sleep, resetting the brain for the next day^[3].

How does sleep benefit the body

Pretty much every part of the body is affected by getting enough sleep – or not enough. Sleep impacts growth and stress hormones, our immune systems, appetites, breathing, blood pressure and cardiovascular health^[4]. Research shows that long term lack of sleep increases the risk of obesity, heart disease and infections^[4]. Sleep also has a profound effect on brain function and emotional wellbeing.

Memory, learning and the importance of sleep

Improvements in learning are associated with a good night’s sleep, with quality long-term sleep enhancing our memories exponentially^[3]. Good-quality sleep increases the function of our cognitive load during our previous time awake and allows us to store memories and learnings^[3].

How does sleep benefit mental health?

Your brain, like your body, needs time to rest and reset at night. Sleep and mental health are closely linked because the brain needs enough sleep – particularly deep, REM sleep - to process information and evaluate thoughts and memories^[5]. It’s believed that a lack of sleep means the brain is not able to consolidate enough positive emotional content, which then negatively impacts mood and mental wellbeing^[5].

Sleep and mood

Research suggests that sleep and our emotions interact, with nearly all psychiatric and neurological disorders expressing sleep disruption, displaying corresponding symptoms of imbalance and suggesting that sleep disruption and mood disorders may be casually related rather than co-occurring^[2]. Data indicates that when we’re sleep-deprived, our brains have an amplified response to negative emotional stimuli, as sleep helps us govern appropriate behavioural responses^[2]. A good night’s sleep is critical for maintaining the functional integrity of the brain, and, possibly, the functional integrity of your relationships.

Metabolism

It’s no surprise that sleep and the body have a very co-dependent relationship. For example, sleep can have a profound impact on our metabolism and hunger cues. One minute you’re tired, and the next you’re standing in front of the fridge with sweat furrowed between your brows, stuffing down the last piece of banana bread. Sleep assists in the regulation of our appetite hormones, leptin and ghrelin. Sleep helps suppress ghrelin (the hormone that increases your appetite) and stimulates leptin (the hormone that signals you’re full)^[6].

How much sleep do we need?

On average, adults need seven to eight hours of sleep per night, young children need at least 10 hours of sleep, while teenagers need at least nine hours. Babies typically sleep about 16 hours a day^[4]. During sleep, the brain goes through four or five cycles, which consist of different stages of sleep[4]. If someone isn’t able to get enough sleep over a period of time, they experience what’s known as ‘sleep deprivation’, which negatively impacts the body  in a number of ways.

Sleep deprivation

Sleep deprivation can impair a range of functions, including the regulation of our metabolism, cognition and immune system^[2]. Prolonged time spent awake weakens the strength of our synapses and overloads our neural networks, inhibiting our ability to perform at our best and take on challenges throughout the day^[3].

How to improve sleep

Some simple tips to help you get better quality sleep – and enjoy all the associated health benefits – are^[7]:

1. Exercise daily, but not too close to bedtime.
2. Make sure your bedroom is quiet, dark and a comfortable temperature (17-19 degrees Celsius is recommended^[8]).
3. Avoid alcohol and caffeine before bed (unfortunately this includes chocolate).
4. Give yourself time to relax and wind down before bed, including switching off devices at least an hour before bed.
5. Create a sleep ritual and stick to it (such as having a relaxing bath or shower and reading before bed), so your body learns to recognise when it’s time to bring on the shut-eye.

The next time someone tells you to sleep on a decision, listen with both ears!

References:

1. De Vivo, L. Bellesi, M., Marshall, W., Bushong, EA., Ellisman, MH., Tononi, G., Cirelli, C. (2017). Ultrastructural evidence for synaptic scaling across the sleep/wake cycle [online]: Science.
2. Yoo, S., Gujar, N., Hu, P., Jolesz, F., Walker, M. (2007). The human emotional brain without sleep – a prefrontal amygdala disconnect [online]: Current Biology.
3. Griffith, L., Robash, M. (2008). Sleep: hitting the reset button [online]: Nature Neuroscience.
4. National Institutes of Health. US Department of Health and Human Services. News In Health: The Benefits Of Slumber. https://newsinhealth.nih.gov/2013/04/benefits-slumber. Published April 2013
5. Sleep Foundation. Mental Health and Sleep. https://www.sleepfoundation.org/mental-health Sourced 22 July 2023.
6. Sharma, S., Kavuru, M. (2010). Sleep and Metabolism: An Overview [online]: International Journal of Endocrinology.
7. Harvard Medical School. 8 secrets to a good night's sleep. https://www.health.harvard.edu/newsletter_article/8-secrets-to-a-good-nights-sleep Published 30 September 2021.
8. Sleep Health Foundation. Hot nights – how to help sleep. https://www.sleephealthfoundation.org.au/hot-nights-how-to-help-sleep Sourced 26 July 2023