Despite the fact we spend 26 years of our lives asleep, until recently we knew surprisingly little about the importance of sleep for health and wellbeing. Read on to learn more about sleep and find out what happens when we don't get enough of it!
How much sleep do we need?
For optimum health, the average adult needs between 7 and 9 hours of sleep every night, while teens should be getting nearer to 9 or 10 hours. Naturally, there will be individual differences when it comes to necessary sleep duration, however, these individual differences should still exist within this range.
Despite the importance of sleep, you will often hear people say that they 'don't need sleep' or they 'only need 4 hours a night', but - to quote Matthew Walker - this is only really true for 0% of the population when rounded to the nearest whole number, and even those few individuals have a specific genetic difference. Everyone else is likely to be so sleep deprived, or so used to being sleep deprived, that they no longer notice the effects or provide accurate reports.
In reality, short sleepers (even famous ones like Churchill and Thatcher) are likely to suffer from sleep-related health problems in later life, including cardiovascular diseases, stroke and dementia.
Despite the need to sleep 7-9 hours per night, it is currently estimated that over a third of adults in the United Kingdom and United States get 6 hours or less, leading some researchers to declare sleep-loss a modern epidemic.
While many of us try to pay off our sleep debt and reclaim lost hours over the weekend, the health costs of a sleep-deprived week are not so easily repaid.
Why aren't people getting enough sleep?
A lot of the time, societal factors outside of our control such as busy work schedules, night shifts and early school start times, mean sleep deprivation has become the norm.
If we want to socialise or take time for ourselves after a long day at work, it is our sleep time that often takes the hit (you can read more about 'revenge bedtime procrastination' in a future post). In fact, humans are one of the only species that deprive themselves of sleep for reasons other than ill-health and food gathering.
It is also worth noting that early school start times are completely incompatible with teenage circadian rhythms, which are naturally shifted towards staying up late and sleeping in (you can read more about teen sleep in a future post).
Coinciding with societal factors, mental health and stress can also play a significant role in sleep loss. Often, we do not have time to wind down properly before going to bed, meaning our minds are still bustling with the day's activities and our levels of cognitive arousal are too high for sleep. At other times, sleep loss can be the result of a more serious problem such as anxiety, depression and insomnia (you can read more about the links between mental health and sleep in a future post).
Why is it so important to get a good night's sleep?
The best way to understand why sleep is so important, is to know what happens if we don't get enough of it.
Compared to individuals who get the recommended 7-9 hours of sleep per night, those who regularly get less than 6 hours per night experience:
Poorer cardiovascular health and increased risk of stroke
Higher levels of inflammation and disease
Lower levels of immunity (including poorer response to vaccines)
Increased cancer risk and speed of tumour growth
Slower rate of healing and skin cell regeneration
Reduced longevity
Decreased fertility and libido (and even attractiveness)
Higher rates of obesity and diabetes
Increased risk of Alzheimer's Disease and other dementias
Poorer cognitive capacity (including attention and memory function)
Poorer impulse control and decision making skills
Increased levels of anxiety, stress and depression
Increased susceptibility to mental illness and suicidal ideation
Poorer social and emotional functioning
Poorer dietary choices and lower levels of exercise
Increased aggression, irritability and negative mood
Poorer academic achievement and work-related performance
Increased risk of car accidents and other injury
For a more in-depth consolidation of the above, I highly recommend Matthew Walker's book 'Why We Sleep', for an interesting and accessible read (you can read my 5 sleep and dreaming book recommendations here).
If you have access to a library/online journals through an academic institution, I also recommend Michael Grandner's book 'Sleep and Health' for an extensive overview.
When we think about keeping fit and well, we often focus on getting regular exercise and making healthy food choices; however without a decent night's sleep, our ability to do either is compromised.
Compared to diet and exercise, sleep has been relatively neglected as a third pillar of health, and is only now being given the research attention it deserves.
The next time you think about setting a health goal, why not try and aim for 8 hours!
References:
Chattu, V. K., Manzar, M. D., Kumary, S., Burman, D., Spence, D. W., & Pandi-Perumal, S. R. (2018, December). The global problem of insufficient sleep and its serious public health implications. In Healthcare (Vol. 7, No. 1, p. 1). MDPI.
Grandner, M. A. (Ed.). (2019). Sleep and health. Academic Press.
Walker, M. (2017). Why we sleep: The new science of sleep and dreams. Penguin UK.
Wild, C. J., Nichols, E. S., Battista, M. E., Stojanoski, B., & Owen, A. M. (2018). Dissociable effects of self-reported daily sleep duration on high-level cognitive abilities. Sleep, 41(12), zsy182.