Not getting enough sleep is correlated with an increased risk of depression, anxiety, weight gain, diabetes, heart disease, stroke and a number of other conditions. Alongside diet and exercise, sleep has a crucial role to play in making us happier, healthier, fitter and smarter.
Since the pandemic began, researchers around the world have been documenting a surge in sleep disorders, fuelled by stress, anxiety and lockdowns, that’s been referred to as “coronasomnia” and just last week yet another study revealed the impact of not getting enough sleep. Researchers at the University of Chicago found that going to bed 75 minutes earlier every night helps you consume 270 fewer calories each day.
Why is sleep so important?
Sleep is when our brain sorts stuff out. It gets rid of any unwanted substances (like toxic proteins that build up during the day), it files and processes new information, it helps produce our immune system and it also helps produce the hormones our body needs. Hormones control a large number of processes in the body and they are finely tuned to our internal biological clocks, with the levels of hormones released in a timed fashion on a daily, monthly, or lifetime basis.
If our sleep is out of sync with what our hormones are doing, we end up with everything out of sync. If you think about how you feel when you’re jet-lagged – all of the body’s processes, from cognitive function to digestion, just don’t seem to be working properly. And not getting enough good-quality sleep is like being in a permanent state of jet lag.
The right amount of sleep
The vast majority – 97 percent of the population – need between six and nine hours of sleep a night. Roughly every 90 to 110 minutes, you’ll go through a full sleep cycle that includes light sleep, deep sleep and dreaming or REM sleep. Almost all of us wake between these cycles, but if you’re not awake long enough to register that, you’ll assume you’ve had unbroken sleep, but it’s quite normal to wake a few times in the night, and not a sign of poor-quality sleep.
How lack of sleep affects you
Digestion and weight
Poor sleep impacts the brain areas responsible for choosing food. Sleep helps to balance out levels of ghrelin, the hormone which controls hunger, and the satiety hormone, leptin. When we are well-rested we can manage our hunger better, and we feel full at the right point.
Stress and cortisol levels
Lack of sleep boosts levels of the stress hormone, cortisol. Cortisol also has an impact on your body composition. Not only is there evidence that high levels of cortisol can cause us to build up abdominal fat, but it can break down muscle tissue – and the less muscle you have, the fewer calories you burn, meaning you’re more likely to put on weight.
Even partial sleep deprivation over one night increases insulin resistance, which can, in turn, increase blood sugar levels. As a result, a lack of sleep has been associated with diabetes, a blood-sugar disorder.
Cortisol plays a part here. Typically it starts rising in the morning to wake us up and is lowest at night when we’re going to sleep, but if you’re not sleeping as your body expects, your cortisol levels can stay high. elevated cortisol levels can have an effect on the brain, causing changes in neurotransmitters that lead to imbalances in serotonin – the happy hormone, which is partly why your mood also suffers.
People tend to experience an increase in negative feelings and a decrease in positive feelings too. Your brain gets excessively emotionally reactive if sleep-deprived, so you can end up irritable and snappy. As a result, lack of sleep is linked to mood disorders such as depression and anxiety.”
Symptoms of depression and anxiety can be linked to disordered sleep. If you treat insomnia, the depression will improve, and if you treat the depression, insomnia will improve.
When you’re rundown, you’re more likely to pick up every bug going – and it’s true. Sleep is crucial to maintaining the body’s immune system. Just a single night of poor sleep leads to a dramatic decrease in natural killer cells – our first-line defense against viruses and potentially cancerous cells. People who sleep six hours a night or fewer are four times more likely to catch a cold when exposed to the virus, compared with those who spend more than seven hours a night asleep.
It’s also why we’re encouraged to rest when we’re ill – and why our clever body makes us feel tired when we’re ill – so that we can sleep more and allow our immune system to respond as efficiently as possible.