Is 8 Hours of Sleep Really Optimal? A Deeper Look into Sleep Duration
For years, the mantra of getting "eight hours of sleep" has been ingrained into our societal consciousness. But is this really the ideal amount for everyone? Scientific evidence suggests that the optimal duration of sleep can vary from person to person and depends on factors such as age, genetics, lifestyle, and overall health. In this post, we will explore the research behind sleep duration and why the often-prescribed eight-hour sleep window may not be necessary for everyone.
Sleep Cycles: Quality Over Quantity
Sleep is not just about how long we sleep, but also about how well we go through the different stages of the sleep cycle. Each night, our bodies cycle through five stages of sleep, divided into non-rapid eye movement (NREM) and rapid eye movement (REM) phases. Research shows that a complete sleep cycle lasts about 90 minutes and involves deep sleep (where physical restoration occurs) and REM sleep (critical for memory consolidation and mental health).
A study published in PLOS Biology demonstrated that the number of completed sleep cycles, rather than the total hours, plays a pivotal role in how rested and functional we feel the next day . For some people, five to six cycles (equating to 7.5 or 9 hours) may be optimal, while others can thrive with just four cycles (around six hours).
Variability Based on Genetics
While the eight-hour guideline is a general recommendation, studies show that individual sleep needs vary greatly due to genetic factors. Research published in the American Journal of Human Genetics identified a gene called DEC2, which is linked to people who function optimally on just 4-6 hours of sleep per night. While these “short sleepers” are rare, the research emphasises that a one-size-fits-all approach to sleep may not be appropriate .
Age and Sleep Duration
The National Sleep Foundation has outlined that sleep needs change throughout life. Younger adults (18-25) and adults (26-64) typically need between 7-9 hours of sleep, but older adults (65+) may only require 7-8 hours . For some men over 40, maintaining deep and restful sleep may take precedence over hitting an arbitrary eight-hour target, especially as the ageing process can affect how long we stay in the restorative stages of sleep.
Shorter Sleep with High Efficiency
The quality of sleep is as important as the quantity. Individuals with high sleep efficiency (the ratio of time spent asleep compared to time spent in bed) can often function perfectly well on less sleep than those with lower sleep efficiency. A study in the Journal of Sleep Research showed that individuals with higher sleep efficiency scores required less time in bed to achieve restorative sleep, and their cognitive and physical performance was not compromised by shorter sleep durations .
The Case for Sleep Flexibility
Incorporating flexibility in our sleep schedules based on our bodies' feedback may be a healthier approach than rigidly adhering to the eight-hour rule. For example, polyphasic sleep, a sleep pattern involving multiple naps throughout the day, has been used by some of the most successful individuals in history, including Leonardo da Vinci and Nikola Tesla.
A study in the journal Sleep found that people who adopt flexible sleep schedules may experience similar cognitive benefits to those who sleep in one long stretch, so long as they reach enough deep sleep over a 24-hour period .
Conclusion: Bespoke Sleep Solutions
While the "8 hours of sleep" recommendation is a good starting point, it is essential to recognise that individual needs vary based on genetic predispositions, age, and sleep efficiency. The goal should not be to strive for an arbitrary number but to focus on the quality of sleep and whether we’re completing enough sleep cycles to restore our bodies and minds.
Understanding your personal sleep needs, potentially through sleep tracking or consultation with a sleep expert, can lead to better long-term health outcomes than following universal guidelines. Whether your optimal sleep time is 6, 7, or even 9 hours, the key is ensuring that you wake up feeling rested and ready to take on the day.
Scientific References:
- National Sleep Foundation. (2020). "How Much Sleep Do We Really Need?"
- American Journal of Human Genetics (2019). "DEC2 Gene: Short Sleepers and the Science of Reduced Sleep Needs."
- PLOS Biology (2017). "The Importance of Sleep Cycles in Sleep Restoration."
- Journal of Sleep Research (2018). "Sleep Efficiency and Its Relationship to Shorter Sleep Duration."
- Sleep Journal (2021). "Flexible Sleep Patterns and Cognitive Function: A Review."
