Getting a good night’s sleep is essential for maintaining physical and mental health. The American Academy of Sleep Medicine and the Sleep Research Society [1] released a joint consensus recommending a threshold of 7 to 8 hours of sleep daily to promote optimal health.
Sleep is necessary for life and crucial to human health. It plays a vital role in brain functioning, including:
- Safety-related and cognitive performance
- Neurobehavioral performance
- Clearance of brain metabolites
- Memory consolidation
- Mood regulation
In addition, sleep influences physiological functions, including:
- Metabolism
- Immune and hormone function
- Appetite regulation
- Cardiovascular system
Sleep deprivation is associated with cerebrovascular and cardiovascular diseases, obesity, cancer, diabetes, and depression. It is also associated with mortality risk.
However, the guidance on recommended sleep duration is aimed at the general public. The recommended amount of sleep should be individualized, meaning athletes might need longer sleeping time, for example, while those who want to excel academically might need less sleep than athletes [2].
Insufficient sleep
In adolescents, poor sleep may be attributed to extrinsic factors such as lack of physical activity, caffeine use, artificial light, increased communication and information technology availability, and no bedtime rules in the household [3].
Meanwhile in adults, lack of sleep is attributed to lack of physical activity, artificial light at night, poor sleep hygiene, caffeine consumption, work demands, health and affective problems, social commitments and family dynamics.
In older adults, sleep patterns change, with many finding it harder to fall asleep while others have trouble staying asleep.
Most older adults experience a morning chronotype, a circadian shift that results in older adults going to bed early and rising early. Research has shown that sleep duration in adults does not change with age.
However, in older adults, the ability to get the needed amount of sleep changes with age. Decreased ability to sleep in older adults is related to medications or polypharmacy, the aging process and health comorbidities.
How much sleep is generally needed to avoid health conditions associated with lack of sleep?
Cardiovascular disease
A review of several meta-analyses showed that short and long sleep duration was associated with the development of hypertension and cardiovascular diseases.
Sleeping for only 5-6 hours a day or sleeping as much as 9-10 hours a day can wreak havoc on your heart’s health and lead to increased blood pressure, increasing your risk of stroke.
The optimal sleep duration to avoid the risk of heart disease and stroke is 7-8 hours of sleep a day.
Metabolic health
Sleep deprivation is associated with reduced whole body and cellular insulin sensitivity, lowered glucose tolerance and increased release of cortisol in the afternoon and the evening. It should be noted that cortisol is an antagonist of insulin [4].
High levels of cortisol decrease the body’s ability to be sensitive to insulin, which facilitates the transport of glucose into the cells.
If the effects of sleep restriction on insulin sensitivity and glucose tolerance continue for long periods, this can compromise the ability of the pancreas to release insulin and result in type 2 diabetes mellitus.
In addition, sleep deprivation is also linked to the development of obesity and metabolic disorders.
Immunologic health
In a study [5] published in the Archives of Internal Medicine, a total of 153 adults who were aged 21 to 55 years old were recruited to examine the effects of sleep duration and sleep quality on susceptibility to the common cold.
The findings of this study revealed that those who slept for less than 7 hours were almost three times more likely to develop a cold than those who slept for 8 hours or more.
Mental health
Numerous publications have assessed the relationship between lack of sleep and mental health or psychiatric symptoms.
Although these studies varied in their study designs, population samples, and outcomes, the findings consistently showed a negative relationship between lack of sleep and mental health.
Those who slept for less than 7 hours were more likely to develop poor mental health than those with longer sleeping times.
Chronic sleep deprivation, about 4-5 hours of sleep daily, increases the risk of depression and other mental health symptoms.
Human performance
Cognitive performance has been validated to be influenced by sleep duration.
Studies have shown that the shorter the sleep duration, the more likely an individual will experience deficits in cognitive performance. Further, when exposure to sleep restriction is prolonged, this results in more significant cognitive deficits.
Interestingly, it is observed that splitting sleep schedules throughout the day to reach a total of at least 8 hours of sleep a day still results in better cognitive performance. This means that sleeping for 8 hours or splitting the sleeping schedule throughout the day would still yield the same results in improving mental performance.
Hence, you can choose to sleep straight for 8 hours or split this into 6 hours in the evening and 2 hours of napping in the day.
Cancer
A study [6] published in the British Journal of Cancer revealed that long and extremely short sleep durations were associated with an increased risk of colorectal cancer in women in postmenopausal.
In addition, short sleep duration was associated with ovarian, breast and general cancer diagnoses.
Pain
Pain symptoms appear to increase with shorter sleep duration. Evidence from literature [7] has suggested that shorter sleep duration increases the risk of pain symptoms and distress.
Sleep duration of less than five to six hours a night was associated with increased pain symptoms, while sleep duration of 7-8 hours was linked with reduced pain symptoms.
Findings from studies provide additional evidence of the importance of appropriate sleep duration in managing bodily pain.
What is the recommended amount of sleep per night?
National Health Service (NHS) guidelines [8] recommend at least 7-9 hours of sleep each day to prevent illnesses and susceptibility to the common colds and reduce the risk of all-cause mortality.
What are the physical changes after a whole week of sleep deprivation?
A digital example [9] that showed the effects of week-long sleep deprivation were shocking.
Using the anime Sam and Sally, the digital creators of the project showed that well-rested characters would look happy and have clear and healthy skin when sleeping for at least 8 hours a day.
The same digital images showed that 24 hours of sleep deprivation would reveal dark circles under the eye, tremors and puffy eyes. People experiencing this amount of sleep deprivation exhibited fatigue, drowsiness, increased risk of making mistakes and decreased alertness.
Seventy-two hours of sleep deprivation would result in microsleeps during the day that lasts up to 30 seconds without the person being aware of it. The project’s creators stated that these could severely affect cognitive performance.
Individuals who have been sleeping deprived for three days would begin to show the following:
- Compromised immune systems
- Increased inflammation
- Extreme fatigue
- Slow reaction time
- Poor memory
- Impaired decision-making
Sleep deprivation for four days would result in hallucinations and difficulty staying awake.
Others at this stage would experience depersonalization, which is a feeling that your surroundings are not real. In addition, you would experience increased stress, fatigue, anxiety and irritability.
Five days of being sleep deprived would worsen hallucinations and all the other symptoms experienced when sleep deprived for four days. Apart from disordered thinking, you begin to have more frequent microsleeps.
Six days of being sleep-deprived results in severe distortion and perception of reality. The urge to sleep becomes unbearable. You can also have psychosis, which is the inability to perceive and process information accurately.
Warning signs that you are sleep deprived
Here are some warning signs that you are sleep deprived:
- Pale and sallow skin
- Red and puffy eyes with dark circles underneath the eyes
- Low mood
- Putting on weight
- Recurring common colds
Take home message
Getting the appropriate amount of sleep daily is critical in improving cognitive performance, preventing obesity and type 2 diabetes mellitus, improving overall mental health and memory, and boosting immunity against the common cold.
Ensure that you are sleeping well to avoid the consequences of sleep deprivation. Sleeping well translates to better emotional and physical health.
Consider reducing caffeine intake to improve sleep. You can also exercise during the day for better sleep at night. Turn off artificial lights at night to ensure better sleep.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4507722/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267703/
[3] https://pubmed.ncbi.nlm.nih.gov/27027988/
[4] https://pubmed.ncbi.nlm.nih.gov/20585000/
[5] https://pubmed.ncbi.nlm.nih.gov/19139325/
[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3553538/
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2527580/
[8] Insomnia – NHS
[9] https://www.happybeds.co.uk/blog/sleep-deprived-sally-the-physical-effects-of-poor-sleep
