Have you ever met one of those people who feel completely fine and refreshed in the morning, despite only sleeping for just four or five hours? Meanwhile, you feel like the human embodiment of exhaustion – despite having over seven hours of slumber?
Now researchers have suggested just how much sleep you need to feel rested; and it could all be down to your genes.
It is estimated that the average person will spend 26 years asleep during their lifetime.[1] It is one of our most important functions: good quality sleep at the right time of day is essential for maintaining neural pathways, allowing you to learn, memorise and process information. Researchers at the University of California in San Francisco have now uncovered the specific role that our genes play in how much sleep we really need.[2]
What happens when we sleep?
Some research has suggested that through sleep, our brains can restore their energy; during non-REM sleep (i.e. dreamless sleep), our brain uses only about half the amount of glucose (which is converted to energy) as it does when we are awake.[3] Although scientists aren’t yet sure of the specific reasons why, there has been lots of evidence to suggest that sleep deprivation causes issues with memory and problem solving, as well as a decrease in attention span and emotional control.[4]
How do we know when to sleep?
While we may think that we sleep when we feel tired, or when we know we are going to have to leave the house for work in 8 hours, so we should probably get some rest, there’s far more going on inside our bodies behind the scenes.
When we sleep is mainly dictated by a biological mechanism called a circadian rhythm – otherwise known as the body clock. Circadian rhythms direct almost all daily activities within your body, from metabolism and body temperature, to hormone release and wakefulness. Your circadian rhythm is synchronised to your environment, such as the amount of light and the temperature, although interestingly your circadian rhythm continues despite a change in the environment. This is why we get jet-lag: when your internal body clock is out of synch with the external clock (i.e. the time of day).
There are specialised cells in the retinas of the eye which process light and inform the brain, where the circadian clock is located, whether it is day or night. This information can therefore cause changes in our sleep-wake cycle – if there is a lot of light at a time when you’re usually supposed to be asleep, you may find yourself struggling to doze off.[5]
While the circadian rhythm determines when you need to sleep, sleep-wake homeostasis, or the homeostatic drive, plays a role in keeping track of how much of it you need. The homeostatic drive isn’t well understood, but what we do know is that it is this which makes you feel more and more ‘sleepy’ the longer you’ve been awake, and determines how deep your sleep is.[6]
So how much sleep is enough?
Researchers at the University of California studied a family with a mutation in the ADRB1 genes, who appeared to require fewer hours of sleep than most people. This gene encodes a receptor for a compound called adenosine; adenosine receptors are one of the key targets of caffeine. From their research, the scientists determined that how much sleep you need to feel rested is dependent on the presence of this mutation. Although it is worth noting that there are a number of other factors, including the genes responsible for the circadian rhythm, which also play a role in how much sleep you need.
Conclusion
So, if you’re one of those people who can’t quite function on less than eight hours of sleep, don’t worry about it – you can’t change what’s in your genes!
By Marta Zima
