Written by Becca Hamilton on Dec 27, 2021.
Scientifically fact checked by Kokoon.
We Shed Some Light (and Dark) on Chronotypes
First, let’s start with circadian rhythms.
Everyone has their own a circadian rhythm, their very own sleep-wake regulator that runs in 24-hour cycles. During these 24 hours a human experiences physical, behavioural and mental changes as they respond to light and dark. This is also commonly known as the sleep-wake cycle. Circadian rhythms help organisms time their daily and seasonal activities, so they’re synchronised with the outside world.
Now to Chronotypes…
Although we all adhere to the body’s circadian rhythms, we don’t all express them in the same way or at the same time. We all have our own personal timer/clock which sets the timing of our circadian rhythms to the outside world - this is known as our chronotype.
A chronotype is your personal disposition to the time of day when you are most active and the time when you need to rest and sleep. Throughout the day, your ability to perform certain tasks and skills changes, as different hormones and alertness levels are present in the body.
Do you naturally wake up early? Go to bed late? Maybe you experience a lull of energy midway through the day. All of these factors are related to an individual’s chronotype.
Your biological clock helps to regulate sleep patterns, feeding behaviour, hormone release, blood pressure and body temperature - and therefore these all have an endogenous timing set by your chronotype.
What Chronotypes Are There?
- Early lark: This chronotype has an early circadian phase and is more of a morning type.
- Lark: This chronotype rises early and is more active in the morning.
- Dove: This is the most common chronotype and covers over ⅓ of the population - they sit somewhere in the middle of the rest of the chronotypes.
- Owl: This chronotype sleeps late and has productivity peaks in the middle of the day and again at night.
Late Owl: This chronotype sleeps later than the Owl, goes to bed much later than the average person and is more active in the evenings when they experience an energy peak.
Body Clock and Chronotypes
Biological clocks produce circadian rhythms and regulate their timing, whilst body clocks keep your body’s processes on track and to a schedule.
Your master clock, which is located in the suprachiasmatic nuclei (SCN) which is inside the hypothalamus part of the brain, is made up of approximately 20,000 neurons and controls all the biological clocks in the body. The master clock is influenced by environmental stimuli/zeitgebers such as light–dark cycles.
Leading Chronobiologist Roenneberg describes how our “chronotypes react as individual clocks respond to light and darkness and how long an internal day they produce”.1 So, whatever chronotype you are, it’s mostly out of your control.
PERIOD (PER) Protein and Chronotypes
A significant part of the biological and body clock is a protein called PERIOD (PER). Salk Institute describes how “the number of PER proteins in each of our cells rises and falls every 24 hours. Our cells use the level of PER protein as an indicator of the time of the day and tells our body when to sleep or be awake.”(2) This can vary depending on what type of chronotype you are, which can change with age.
It seems that children are early chronotypes and become later chronotypes as they develop, peaking at the age of 20. As they age beyond 20, their chronotypes can change and become earlier.
However, if they’re naturally a night owl, shedding the late-sleeping skin of their youth won’t necessarily turn them into a morning person. They may still be a night owl as they grow older, but just less extreme.
An individual is likely to retain their chronotype throughout their lifetime, which points to chronotypes being partly genetic. However, due to modern living we can’t always live by our chronotype thanks to things like having a roommate who keeps you up late or forces you to switch the lights off before you’re ready. As well as shift work, work schedules, stress, blue lights and the list goes on...
And it turns out that living outside of our chronotype (whether by choice or not) isn’t always great for our health. As a result, it can be a contributing factor towards quite a few health issues. But there’s no need to worry as we can do something about it!
How Can We Live In Sync With Our Chronotypes?
A small town in Germany called Bad Kissingen of 20,000 citizens became the world’s first ChronoCity (3) in 2013. Dr. Thomas Kantermann, a Chronobiologist and the town’s Chief Scientific Officer, wanted to address problems related to the lack of sleep by looking at both the behavioral and the environmental causes of sleep disturbance. He studied peoples’ circadian rhythms and sleep patterns, making practical changes to school and work schedules, so residents could fulfill their natural sleep needs.
Although we may not have the luxury of living in a ChronoCity, we can do our own chrono-hacking, by finding out what our chronotype is and trying to adjust our schedule and avoid disruptors that could throw our chronotype and circadian rhythm out of sync.