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How sleep loss affects your health? What happens inside a sleep-deprived body? Seek no more, we have some answers.

Despite countless benefits of sleep, sadly, a lot of us regularly experience sleep-related problems.

“22% of people in the UK struggle to fall asleep every single night. A further 15% struggle to fall asleep at least once a week”^[1]

Whether you suffer from insomnia or not, you probably experienced a sleepless night at some point in your life. If you wonder how sleep loss affects your health, seek no more.
To understand what happens inside a sleep-deprived body, we’ll first take a look at what occurs during sleep and why this process is essential to your health.

Sleep is a physiological process that is crucial for maintaining body homeostasis. It’s the time when body cells regenerate, allowing tissue growth and muscle repair. During sleep, the body removes toxic by-products, releases vital hormones and proteins, restores the energy, and allows the formation of long-term memory. What we usually perceive as a time of being the least efficient, for the brain and body sleep is truly the exact opposite- it is a time of hard work.
But what happens when the body is deprived of such an important process?

Understand the impact of sleep loss:

1. Rise of cortisol levels.

A study^[2] performed on a group of young men concluded that sleep loss could distort the body’s stress response and thus, might increase cortisol levels. Cortisol, also known as the stress hormone, is the chemical produced by the adrenal glands and it’s responsible for self-preservation during threatening situations. It becomes activated whenever a potential threat is perceived, preparing one for fight-flight-or freeze response. In this regard, cortisol secretion is extremely important. However, the last thing you want to happen is for your body to flood with cortisol for no particular reason. It has been suggested that, since the body preserves and recharges our energy during sleep, high levels of cortisol following a sleepless night are associated with the body’s effort to produce enough energy to stay awake.
“Studies have shown that insomnia and other forms of sleep deprivation cause your body to secrete more cortisol during the day, perhaps in an effort to stimulate alertness.”^[3] The long term stress exposure may contribute to a vast amount of health problems, amongst others: heart disease, digestive issues, weight gain, depression and anxiety.

2. Elevated blood pressure.

“A bad night’s sleep may result in a spike in blood pressure that night and the following day, according to new research led by the University of Arizona.”^[4]

Sleep helps the body regulate hormones thus, over time, inadequate sleep or bad sleep quality may cause shifts in those hormones, resulting in high blood pressure. That, unfortunately, poses a risk to one’s cardiovascular health. Following a study^[5] on 300 women and men with no pre-existing heart conditions, researchers from The University of Arizona found that even one, or a few nights of bad sleep can cause spikes in blood pressure. Hypertension increases the risk of a stroke, heart attack and even death. Sleep experts recommend between 6 and 8 hours of sleep each night to reduce one’s risk of cardiovascular disease.

3. Disrupted body heat regulation.

Thermoregulation is the ability to regulate (or maintain) one’s own core body temperature through a vast number of internal body processes. Our core body temperature plays a key role in sleep. Working in perfect harmony with a circadian rhythm^[6], it fluctuates up and down throughout a 24-hour cycle. It drops around bedtime, which signals to the body that it is time to prepare for sleep. Naturally, during sleep, it drops about 1°C, allowing rest and energy preservation. It has been observed that sleep deprivation alters this natural rhythm of thermoregulation^[7] One study^[8]involving six healthy, young women, found that in the long term, sleep loss causes individuals to be more vulnerable to heat loss and reduces their ability to warm, even in thermally comfortable environments. Therefore, researchers believe that sleep deprivation disrupts natural body heat regulation.

4. Lower response of the immune system.

We need sleep in order to keep our immune system healthy. Lack of it, or reduced quality of sleep, could make us more prone to catching infectious diseases and might decrease our ability to fight them. Lack of sleep suppresses the immune system due to deficiency of the disease-fighting substances that are normally released during sleep. Research^[9] has shown that persistent sleep loss and the body’s natural stress response that goes with it, not only weakens the immune system but also causes low-grade inflammation in the body. During sleep, there is an increased production of cytokines, which are pro-inflammatory proteins that help the body recover if a person is sick or injured. Experts believe that this happens in an effort to strengthen adaptive immunity. However, normally, this low-grade inflammation goes back to normal before a person wakes but it continues with people who don’t sleep enough.^[10]

5. Risk of obesity and type2 diabetes.

Good night’s sleep plays a significant role in appetite regulation and maintaining a healthy weight. Poor sleep quality, however, affects metabolic processes in the body, particularly the regulation of hormones responsible for healthy eating patterns. The two primary hormones associated with appetite are ghrelin and leptin. Ghrelin increases appetite by sending hunger signals to the brain, whilst leptin, an appetite suppressor, sends signals of being full. Poor sleep decreases levels of leptin and elevates ghrelin levels, which correlate with increased appetite, particularly for energy-dense foods. This, eventually, may lead to obesity and, due to the impaired glucose metabolism^[11], type 2 diabetes.

5. Emotional instability.

Sleep restriction has been linked to higher emotional reactivity and impaired emotion processing. Even one night of bad sleep may cause you to react more impulsively to a negative stimulus than you normally would. Irritability, anger and exhaustion go hand in hand and can really make your day more difficult than it needs to be. The part of the brain responsible for emotional response, the amygdala, is more reactive when an individual is sleep-deprived. Researchers speculate that it could be due to hindered communication between the amygdala and the prefrontal cortex, part of the brain responsible for cognitive functions, like focusing one’s attention and impulse control. That’s why individuals who don’t sleep well are more likely to experience low moods and have a more negative outlook on life. Sleep deprivation that persists over a long period of time may induce certain mood disorders, like depression, anxiety or seasonal affective disorder (SAD).

5. Decrease in cognitive functions.

Researchers^[12]support the thesis that sleep deprivation harms attention and working memory. It has been suggested that this occurs due to the vulnerability of the prefrontal cortex, which, amongst its other functions, allows decision-making, problem-solving and planning. When lack( or bad quality) of sleep comes into play, those processes become more difficult to execute. Drowsiness and a slowed reaction time are another, and probably the most dangerous, downfalls of sleep loss. Driving a vehicle after a sleepless night has been compared to driving after alcohol.

“[…] Going over 24 hours without sleep is equivalent to having a blood alcohol content level of 0.10%”^[13]

Accidents caused by sleep-deprived drivers are unfortunately very common. It is best to avoid driving if you haven’t slept well and are feeling drowsy.

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Research references

1. https://www.linenbundle.com/blogs/news/insomnia-statistics
2. https://pubmed.ncbi.nlm.nih.gov/9415946/
3. https://www.healthline.com/health/cortisol-and-sleep
4. https://www.sciencedaily.com/releases/2019/06/190604131159.htm
5. https://www.sciencedaily.com/releases/2019/06/190604131159.htm
6. https://nigms.nih.gov/education/fact-sheets/Pages/Circadian-Rhythms.aspx
7. https://pubmed.ncbi.nlm.nih.gov/19002705/
8. https://pubmed.ncbi.nlm.nih.gov/9485537/
9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256323/
10. https://www.sleepfoundation.org/physical-health/how-sleep-affects-immunity
11. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2929498/
12. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2656292/
13. https://www.sleepfoundation.org/sleep-deprivation/how-to-function-after-sleepless-nights