Do Your Genes Determine Your Sleep Time – or is it Something Else?
It is 6 a.m. and I am writing this post. I love the silence of the early morning and watching the slow illumination of the day as the sun rises.
I didn’t always wake up so early.
In fact, I remember seeing the sunrise at the end of a long “night on the town” when I was younger. In those days I wouldn’t think of going to bed before 1 a.m.
Although we talk about being a “morning person” or a “late night person,” our preferences can change with age. It is common for young adults to stay up late into the night and for older adults to wake up early.
The concept of a preferred time of day to be awake is called a “chronotype.”
The notion is that we are each genetically predisposed to different times of day to be awake and asleep.
There are whole areas of research devoted to understanding these preferences, why they may exist, and their implications.
One popular sleep specialist has even written a book describing different chronotypes and when you should be engaging in various activities, accordingly. It even includes what time to have sex! (He doesn’t advise on what to do when your partner is of a different chronotype).
How To Find Your Chronotype
First, consider your behavior during free days; weekends or holidays when you are not required to be up at any particular time. Now answer these three questions:
What time do you usually go to sleep?
What time do you usually wake up to get out of bed?
What is the middle of those two times - what is the midpoint of your sleep? (For example, if you usually go to sleep at 11pm and wake up at 7am, the midpoint would be 3:00 am.)
Look at the graph below to find your chronotype. To be classified as a “night owl” according to this assessment, your midpoint of sleep would be later than 6:30 am. You can see that 21% of the population are considered to be night owls.
(Developed by top chronobiology scientist, Till Roenneberg)
Do chronotypes really exist?
The idea of each of us having a unique preferred time of day is appealing and bears out according to our observations.
Different people have preferences for when they want to go to bed and fall asleep.
However, there is a glitch in all this research on chronotypes.
It is being conducted under artificial circumstances.
That is, in our modern world we are able to stretch out the day with artificial lighting. And we do. As you can see from the graph above, an extreme “night owl” with a midsleep of 12 noon, getting 8 hours sleep, would be going to bed at 8 a.m. and getting up at 4 p.m.
Is this really genetically programmed behavior?
Or is it simply an aberration, given the opportunity to stay up as late as we please, all the entertainment available to us, and the addictive nature of scrolling through our social media?
It is easy to procrastinate going to bed at night, it’s a time when we can relax without feeling guilty or catch up on work that didn’t get done during the day.
Studies conducted in natural settings have found that when people are subject to the natural rhythms of the day, they synchronize.
In these conditions, all “chronotypes,” even extreme night owls, fall into a very similar routine. They all fall asleep between 9 and 10 p.m. and wake up just before dawn — after just two days of camping.
Furthermore, there are negative health implications to being on the “night owl” end of the spectrum.
When you consider that this extreme preference is a modern invention and that mother nature would probably not have programmed some of us to become sick according to such a preference, it’s doubtful that these extreme chronotypes are genetically programmed.
Perhaps the truth is somewhere in the middle.
We do have preferences according to the time of day to be awake and asleep.
However, the genetic variation may be much less extreme than we see today under conditions of modern lighting.