SLEEP TYPES: WHAT DO OWLS AND LARKS HAVE TO DO WITH OUR INTERNAL CLOCKS?

Are you an early bird or are you best pals with your snooze button? Are you a night owl who brainstorms best in the evening, or Is it ‘lights out’ at 9 p.m.? There are many types of sleep patterns that can affect our habits and our performance — and they also resemble those of our winged friends, like the owl and lark, among others. 

If your motto is less ‘early bird gets the worm’ and more like ‘the early bird can kiss my ass’ then many people have probably already advised you (mostly with good intentions) to try get to up early — and that it’s only a matter of time (pun intended) until you get used to it.

This tip most likely came from a so-called ‘lark’ — a person who can jump out of bed each morning with tons of energy, like a kid heading to school recess. Yes, there are a few specific factors that can affect our morning energy levels. However, it’s really about our routine and how easy we can adjust to a new one... and it’s mainly our genes that determine how our internal clock is wound up.

WHAT ARE THE DIFFERENT SLEEP TYPES?

Our hormone levels, body temperature, performance capacity, as well as our sleep and wake cycles, fluctuate depending on the time of day. When and how these characteristics vary depends on a person's particular sleep type, also called chronotype. This classification influences our internal clock, which synchronises the body's metabolic processes in every cell.

The idea of chronotypes to categorise different types of sleep (including ‘owls’ and ‘larks’) was introduced at the turn of the 20th century by the German psychiatrist Emil Kraepelin, whose team researched how symptoms of fatigue arose in the workplace and how they could describe fluctuations in performance throughout the workday. In the 1950s, it was a Romanian-Austrian-American scientist, Franz Halberg, who coined the term "circadian rhythm" (circa = about; diem = day) to describe this concept as a way of referring to our body’s internal clock. 

WHAT ARE THE DIFFERENT TYPES OF SLEEP?

One of the most important findings that Kraepelin drew from his research was that when it comes to sleep, humans tend to be of two different types: the larks and the owls. The names come from (surprise, surprise…) the behavior of these two feathered creatures.

What are the larks like?

Larks are active in the morning and most alert between 9-11 a.m. As the day wears on, though, their performance declines and the larks get tired early. The American psychologist and self-proclaimed “sleep doctor” Michael Breus explains the performance curve of early risers based on hormone levels. In the case of larks, the hormone cortisol increases early in the morning to break down the hormone melatonin, which is known to make us tired. As cortisol levels rise and melatonin levels fall, the body begins to feel more awake and alive.

... and what about the owls? 

The main difference between owls and larks is that owls are late sleepers and are rarely physically present before 10 a.m. — if mentally present at all. While a regular morning routine can help the system get going, it’s hard for owls to fight their genetic predisposition to take things slow in the morning. People who belong to this sleep type tend to feel more alert in the evening; they likely don’t even feel tired before 10 p.m. But they have no problem hitting the sack for a night either. Among the party animals out there, you’re likely to find more owls than larks.

Other sleep types: lions, bears, wolves and dolphins

Various scientists and studies point out that there are other types of sleep besides larks and owls:

For example, Breus claims there are four different types of sleep: the lion, the bear, the wolf and the dolphin. Whereas the lions are early risers, the wolves the nocturnal, similar to the lark-vs.-owl contrast. According to Breus, bears are most active around noon and follow a sleep rhythm that generally mirrors the rising and setting of the sun. They can get out of bed reasonably well, but they can also stay up longer in the evening without noticing a brutal drop in performance, like in the case of more morning people. Last but not least, Breus calls the more problematic sleepers dolphins because they tend to wake up at night and experience a disturbed sleep schedule. During the day, their waking state fluctuates between awake and tired, and by around 7 p.m. they’re in their prime.

One more sleep type to go: nap and afternoon people

A 2019 survey on 1,305 people concluded that there are a total of five different sleep types, categorised by their most active time of day: morning, intermediate, afternoon, evening and napper.

While the morning and evening types show strong parallels to the larks and owls, the intermediate type is something in-between. Nappers start the day with full power and stay fit as a fiddle until about 11 a.m. Then, their ability to concentrate drops off, and they reach a low point in performance around 3 p.m., at which point this group inevitably feels like taking a power nap. 

The afternoon type is considered a sleepyhead who can’t get out of bed in the morning and wants to hit the hay as early as possible. Their attention span is highest from 11 a.m. to 5 p.m.

What all of this scientific research has in common is that people tend to have differing sleep rhythms that determine how their particular performance curve rises and falls throughout the day. While there are only a couple of comparative studies to support the theory behind Breus’ four animal chronotypes and the napper-afternoon idea, for now it’s safe to at least assume that there are owls, larks and then there are types that live in-between the two.

WHAT FACTORS CAN INFLUENCE SLEEP TYPES?

Is sleep type determined by your genes? That’s only partly true. Many people can adapt their sleeping habits to their individual circumstances, regardless of their internal clock. But drastic changes can also lead to extreme health issues. In addition to genetics, two other important factors that help shape your sleep type are age and environment.

Teenagers versus adults 

Babies and toddlers need a lot of sleep, and their biorhythms tire them out early in the evening. It’s rather unusual for a kid to be (still) dancing on the table come midnight. As teenagers, the internal clock changes, which is why teens typically don't get tired until late into the evening. This is because the body releases the fatigue-inducing hormone melatonin much later. Most teenagers become night owls — ironically after so many years as young larks who enjoy waking their parents up early in the morning.

The tendency to shift into an owl type can linger into old age too. A report of nearly 90,000 individuals revealed that 24.2% of the under 30 years old category preferred mornings, in contrast to 63.1% of those over 60 years old. These results suggest that sleep types tend to change again as we grow older, and that there tend to be more larks among seniors.

Light versus darkness

Melatonin, the sleep hormone that makes us tired, is mainly released in the dark. That’s why if we don’t get outside much during the daytime, we often don’t feel like we’ve really woken up at all. Something similar happens when we’re outdoors too: we get tired when it’s dark out, no matter what time it is. A 2017 study agreed, finding that the time of sunset affects our sleep patterns and that in latitudes where the sun sets earlier, there are more larks/morning people and fewer owls/evening people than in regions where sunset time is later.

However, natural sunset isn’t the only light that has an impact on our internal clock. Artificial outdoor lighting can also slow down the body functions that help us fall asleep. This can help explain why, for example, young people who live in large cities are more likely to become night owls than in rural areas where it gets darker at night. Similarly, the light generated by a screen — like from a TV, smartphone or tablet — can also affect melatonin secretion. The more time a person spends in front of a screen, especially in the evening, the more likely they are to become more owl/evening-type. Or in other words, we become more evening-oriented when the body’s melatonin release is prolonged by more light.

WHAT HAPPENS WHEN YOU IGNORE YOUR INNER CLOCK?

Certain lifestyles, jobs or other circumstances can also play a large role on the type of sleep patterns one can develop. Those who serve as gas station attendants, night guards, nursing staff or taxi drivers, often have to work completely or partially at night at some point in their careers and end up battling their internal clock. The ‘night shift’ (or ‘graveyard shift’) can also have a negative impact on adult circadian rhythms, as can school that starts early at 7:30 a.m. or 8:00 a.m. on nocturnal teenager habits.

It’s also not uncommon for some lark-types to stay out past 10 p.m. due to social gatherings or events, even if their body is craving to stay in for a relaxed evening or call it an early night. Even if these folks are usually easy early risers, when they have to get up early the next day after a late night, the result is often a rough morning, a phenomenon known as ‘social jetlag’.

Adjusting one’s sleep type is often unavoidable — however, should it lead to chronic sleep deprivation, it can become dangerous. Those who don’t get enough sleep can do severe harm to their mental and physical health. 

ALL SLEEP TYPES ARE FINE JUST THE WAY THEY ARE

To close us out, there aren’t any ‘good’ or ‘bad’ sleep types. Obviously, it’s easier for larks to be up and at ‘em by 8 a.m. for school or work. In contrast, an owl is less likely to struggle to keep their eyes open for a late night obligation or event. Regardless, you can lead a wonderful and fulfilling life no matter which sleep type you pertain to — be it a lark, an owl or somewhere in-between. What’s important is not to fight frantically against your inner clock and to instead embrace it. Because trying to turn a real owl into a lark would be a total ‘hoot.’