The Science of Sleep
Sleep plays a crucial role in your mental and physical health. While you sleep, your body undergoes repair and restoration. Lack of sleep can negatively impact your health and wellbeing, leaving you feeling tired and less able to concentrate.
But did you know that sleep is regulated by a host of biological reactions and affected by many environmental factors?
The chemicals and hormones that regulate sleep
Various chemicals and hormones are involved in the sleep-wake cycle – known as our circadian rhythm. (1) The shift between sleeping and waking up creates changes in thousands of neurons in the brain, causing the body to react in specific ways.
Adenosine:
This chemical is said to play a critical role in the sleep cycle. It slows down the neurons’ activity and builds up when we’re awake, causing us to feel sleepy. On the other hand, caffeine suppresses adenosine, helping you to stay awake.(2)
GABA, acetylcholine, orexin, and serotonin:
These are chemicals that activate and deactivate certain cells, by sending signals to the nervous system. These are more commonly referred to as neurotransmitters.(3)
Melatonin:
This hormone plays a vital role in regulating your sleep cycle. As exposure to light decreases, melatonin is naturally produced, promoting sleep.(2)
Cortisol:
Best known as a hormone secreted by the body in response to stress, cortisol also affects your sleep.
Just like your sleep-wake cycle, cortisol follows a similar circadian rhythm.(1) Cortisol is released in small bursts throughout the day. The body slows down the production of cortisol around midnight and generally peaks an hour before you wake up (around 09:00) (1)
Finally, leptin and ghrelin are hormones that regulate our appetite and may impact our circadian rhythms, while adrenaline and norepinephrine are considered hormones that play a key role in the sleep cycle.(3,4)
Other factors that affect your sleep
Here are a few additional factors to consider: (5,6,7)
Genetics:
Based on genetics and other factors, these chemicals and hormones impact people differently. This is why some people are prone to sleep disorders, as they may run in their families.
Lifestyle:
Lifestyle choices such as your diet and exercise routine are also known to influence the chemicals and hormones responsible for the sleep cycle.
The quality of your sleep:
If your sleep is frequently interrupted, you are not getting quality sleep. The quality of your sleep is just as important as the quantity.
Sleep deprivation:
If you haven't been getting good sleep over a period of time, the number of hours of sleep you need increases.
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Pregnancy:
Changes in hormone levels, as a result of pregnancy, as well as physical discomfort can adversely impact the quality of your sleep.
Age:
While it is recommended that adults (i.e. 18 years and older) get at least 7 hours of sleep per night, as you get older, your sleeping patterns may change. You may find that you do not sleep as deeply, that you wake up many times during the night, or that you take longer to fall asleep.
How much sleep do we need?
The number of hours of sleep we need as part of a healthy and balanced lifestyle depends on a number of factors and varies depending on your age. Below is a guideline for the number of hours of sleep recommended per age group.(8)
Age Group: Hours of Sleep per Day
How poor sleep affects your health
One in three people suffer from poor sleep, with stress, screen time and extended working hours noted as contributing factors.8 But did you know that poor sleep leads to more than mood swings and a lack of focus? In fact, research shows that sleep deprivation and poor quality of sleep may put you at risk of serious health conditions, which may shorten your life expectancy, such as obesity, coronary heart disease, and diabetes. (7)
Tips from a medical professional
"As a nurse, I believe this is such an important topic. When we get enough good sleep, we are better able to maintain a healthy, balanced lifestyle," says Elena Tejedor, Nurse Case Manager at Cigna.
"That means that when we take ill, or are recovering from an illness, getting enough sleep forms part of a good treatment plan. While the use of sleeping tablets is an option, they should only be taken for a short period of time and must be prescribed by a doctor or authorized medical professional."
For more tips on how to sleep and eat well, stay active and manage stress, visit our Body and Mind site.
REFERENCES:
1.How Does Cortisol Affect Your Sleep? Healthline. https://www.healthline.com/health/cortisol-and-sleep#cortisol-and-stress. Accessed December 7, 2021.
2.Sleep/Wake Cycles. Johns Hopkins. https://www.hopkinsmedicine.org/health/conditions-and-diseases/sleepwake-cycles. Accessed December 7, 2021.
3.These Neurotransmitters Are Probably Keeping You Up At Night. Forbes.
https://www.forbes.com/sites/quora/2016/10/05/these-neurotransmitters-are-probably-keeping-you-up-at-night/?sh=5cacd9bc1228. Accessed December 7, 2021.
4. Sleep and Overeating. The Sleep Foundation. https://www.sleepfoundation.org/physical-
health/sleep-and-overeating. Accessed December 7, 2021.
5. Sleep disorders. The Sleep Foundation. https://www.sleepfoundation.org/sleep-disorders. Accessed December 7, 2021.
6. Diet and exercise and sleep. The Sleep Foundation. https://www.sleepfoundation.org/physical-health/diet-exercise-sleep. Accessed December 7, 2021.
7.Why lack of sleep is bad for your health. NHS.https://www.nhs.uk/live-well/sleep-and-tiredness/why-lack-of-sleep-is-bad-for-your-health/. Accessed December 7, 2021.
8. Adult health. Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/how-many-hours-of-sleep-are-enough/faq-20057898. Accessed December 7, 2021.