There is a term for the internal process that governs sleeping patterns in humans- it is called our circadian rhythm. The circadian rhythm regulates our sleep-wake cycle within a 24-hour period and it has been recognised as a key player in the quest for longevity.
Medical science has established that there is indeed a genetic component to circadian rhythm, but research has also shown that various external influences can impact the duration and quality of our sleep.
The accumulation of our need for sleep over time, is called our sleep drive. This can be defined as the difference between how much sleep we need and how much sleep we get. Sleep drive can also be regarded as a form of biological pressure, which gets stronger the longer we stay awake and subsides when we achieve adequate amounts of rest and sleep.
Gaining an understanding of your unique circadian rhythm, as well as the factors which affect your personal sleep drive are equally essential prerequisites for achieving a sound night’s sleep.
Furthermore, as these indicators appear to directly impact both physical and mental health, nurturing them is advisable and ignoring them, is the new ‘bad habit’ on the block.
Not all sleep is created equal
Science shows that it is not merely the hours of sleep, but rather the hours of restorative sleep that affect our wellbeing. Despite many medical references for optimal sleep quantities according to age, sleep quality is now globally recognised as a critical determinant of health (1).
For optimum revitalisation, it appears that just sleeping is not enough. More specifically, achieving deep sleep is a necessary requirement. Most adults need 1.5–2 hours of deep sleep per night and there is no minimum requirement for light sleep (2).
REM vs non-REM sleep
There are two types of sleep, namely non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. These occur in short alternating cycles (starting with three phases of NREM sleep, followed by one phase of REM sleep), on repeat while you are asleep.
Deep sleep occurs in the third stage of NREM sleep, which usually starts about 30-45 minutes after falling asleep and only lasts for a few minutes before giving way to REM sleep.
Although the cumulative duration of deep sleep accounts for only 25% of total sleep time in adults, fragmented sleep or sleeping at times that are not concordant with your inherent circadian rhythm may affect your ability to reach deep sleep and diminish your percentage thereof (2).
How quality of sleep affects quality of life
When we are asleep, we allow our bodies vital time for recuperation, rest and repair. Furthermore, sleep supports our metabolism and immune system, and facilitates the processing of our emotions.
Poor quality sleep exacerbates inflammation and stress and is also associated with increased risks for depression, obesity, type 2 diabetes and cardiovascular disease.
The influence of genetics on sleeping habits
Being a ‘night owl’ (naturally inclined to stay up late at night and sleep late in the morning) or an ‘early bird’ (naturally inclined to go to bed early and wake up with the sun) is a pre-programmed component of your DNA. This is called your chronotype.
There is no good or bad chronotype and no right or wrong time to sleep, but within the frenetic demands of life as we know it, our natural circadian rhythms and sleep quality can easily be disrupted by societal norms, inflexible working hours, family responsibilities, artificial light, dietary stimulants and stress.
As a result, the ‘early birds’ whilst still waking at dawn, may be unable to turn in as the sun goes down. On the contrary, the ‘night owls’ will be unaffected by late night expectations, but may find themselves struggling to manage early morning demands. Either way, a lack of sleep or strain on your natural sleep cycle, not only increases your sleep drive, but may actually put strain on your health.
Therefore, establishing an individual sleep pattern that suits your genetic circadian rhythm, has been identified as an imperative way to manage exhaustion and optimise both physical and mental wellbeing.
With the incredible advancement of genetic testing in recent years, (including increased accessibility at consumer level), it is relatively easy for everyone to discover their genetic chronotype.
Although multiple genes have been shown to influence circadian rhythm, the CLOCK gene has been identified as a pivotal predictor of innate sleeping patterns. This gene can be examined to guage the probability of morning or afternoon fatigue, as well as associated food consumption patterns, which if left unchecked can result in weight gain tendencies for ‘night owls’ who regularly indulge in late night snacking.
Knowing which genetic variation of the CLOCK gene you carry will help you to prepare a suitable sleep schedule, to plan exercise at the time of day that your energy levels are optimal and to plan eating windows that support weight management.
A 3X4 Genetics Test can provide personalised insights into your own circadian rhythm and inherited variant of the CLOCK gene. To find out more, click here.
The supply and demand of sleep
It is well established that sleep efficiency declines with age. Nevertheless, in order to foster longevity, achieving a state of sleep equilibrium (a balanced, regular pattern of sleep) is essential at every age.
When demand > supply: Middle aged adults need more sleep but have less sleep opportunity than the elderly. However, seeing that the cumulative effect of insufficient sleep can trigger a cascade of physiological dysregulation, inflammation and health risk, prioritising sleep is an important health investment and it is never too early (or late) to start.
When supply > demand: The elderly may require less sleep due to reduced physical activity, but the ability to fall asleep also becomes more difficult, as the production of melatonin (the regulatory ‘sleep hormone’ produced in response to darkness) declines with age . Moreover, whilst the elderly may have more sleep opportunity, too much time spent in bed can also be detrimental to physical and mental health. Hence, sleep scheduling remains vital, regardless of sleep opportunity (3).
The last word
Goodnight. Not quite.
Although sleeping rhythms may designed by nature, there are many effective habits, that if nurtured persistently can improve sleep quality.
If you are a poor or inconsistent sleeper, look out for the next blog on Lifestyle solutions for a sound night’s sleep, which will address some of the practical tools for optimal sleep management.
References:
- https://www.nature.com/articles/s41598-021-03997-z
- https://www.healthline.com/health/how-much-deep-sleep-do-you-need#stages-of-sleep
- https://www.ncbi.nlm.nih.gov/books/NBK19956/