Have you ever noticed that some people wake up beaming before sunrise, while others don’t seem to shine until evening hours?

It’s not simply preference or habit–how and when we sleep is actually managed by genetics to some degree. Called phenotypes in the science world, see how these biological preferences work and what they mean for you.

What is a Sleep Phenotype?

A phenotype in genetics is a set of observable characteristics that result from the interaction of one’s genotype (instructions carried with genetic codes) with the environment.

It basically refers to how genetic information is expressed in reality. Phenotypes are the observable things like eye color, hair color, height, shoe size, some behaviors and other traits. 

Now in terms of sleep, studies have confirmed a significant heritability of usual bedtimes, sleepiness and sleep duration with links to genes that regulate various components of the circadian clock.

Sleep phenotype (also known as chronotype) refers to an observable pattern of behaviors with genetic links, in this case, tendencies toward earlier bedtimes and wake times or later bedtimes and wake times, and schedules in between.

Health & Habits: What Sleep Phenotypes Mean for You

Researchers are interested in phenotypes for the insights they can provide on behaviors, health, and other related or associated expressions.

You don’t need genetic testing to figure out your sleep phenotype—simply consider your sleep habits and normal schedule. Think about when you naturally fall asleep and wake up when you aren’t using an alarm clock or don’t have to get up at a specific time for work or school.

Several studies have linked sleep habits with specific traits or health concerns, which can be helpful to know about. Read on to see what research has found regarding early and late sleep phenotypes.

Early Birds

The early phenotype or “lark” naturally goes to sleep earlier, around 9 to 10 pm, and wakes earlier, around 4 to 6am. Some extreme “larks” may feel pulled towards an even earlier schedule.

Habits of Early Birds:

  • Your energy levels and productivity are highest in the morning to late morning.
  • You might find it hard to do intense tasks late at night or work evening shifts.
  • Early birds do slightly better in school, and are more likely to be logical and analytical and favor concrete information sources, according to a University of Madrid study.
  • Early birds are also slightly more proactive, which possibly translates into habits like getting better grades and thus better employment opportunities, according to a German study.

Early Birds & Health:

  • Morning people tend to be happier, more positive and report feeling healthier, according to a University of Toronto study.
  • People are more likely to become early birds with age due to natural biological changes.
  • You’ll likely feel best exercising early in the morning.

Famous Early Birds:

  • Avon CEO Andrea Jung
  • President George HW. Bush
  • President George W. Bush
  • Author Ernest Hemingway
  • French Emperor Napoleon
  • Author John Grisham
  • Benjamin Franklin

Night Owls

Late phenotypes or “night owls” naturally sleep later, around 12 to 4 am, and wake later, around 8 to 12 pm. The most extreme cases are people whose days and nights are almost completely flipped.

Habits of Night Owls:

  • Your energy levels and productivity are highest in the afternoon to early evening hours.
  • You might find it hard to wake up for early morning jobs, workouts or classes.
  • Night owls are more likely to be imaginative and creative according to the Madrid study. Another study found that night owls scored higher on tests of creativity than intermediate or early types.
  • Night owls tend to have higher IQ scores, however night owl students also tend to perform worse academically compared to larks.
  • An Australian study found that night owls were more likely to show the “Dark Triad” of personality traits: Machiavellianism, narcissism and psychopathy. The psychologist behind the study also said night owls were more prone to darker behaviors like cheating, risk taking and were more prone to depression, dishonesty and boom-bust work patterns.

Night Owls & Health:

  • Teens who sleep later on school nights (after 11:30pm) get less sleep and are more likely to suffer emotional distress and poorer academic performance than earlier sleeping peers, according to a large-scale data study conducted by University of California Berkeley researchers.
  • Late risers may be more prone to weight gain and are more likely to be overweight.
  • Night owls are more likely to suffer depression and sleep problems, especially women and older evening types.
  • You’ll likely feel best exercising in the evening.

Famous Night Owls:

  • British Prime Minister Sir Winston Churchill
  • President Barack Obama
  • President Bill Clinton
  • Inventor Thomas Edison
  • Artist Henri de Toulouse-Lautrec

If neither night owl or lark describes you, then you’re actually quite normal, so no worries! Only around 20% to 40% of people fall into true night owl or lark categories. The majority of people fall in the middle, or have slight preferences for late or early schedules.

In terms of trying to change sleep habits, we can’t quite change our chronotype (i.e., our genetics), but there are things people can do to normalize their sleep schedules for better health and well-being, according to circadian scientist Jade Wu, PhD of the Duke University School of Medicine. 

“You can’t choose your chronotype, just as you can’t choose your height,” Wu says, “But you can ‘fake it ‘til you make it’ by nudging your genetically determined nature. Just as a kid can potentially nudge their height higher by drinking more milk and being physically active, a night owl can maximize their well being by keeping a consistent sleep-wake schedule and getting lots of bright light in their eyes first thing in the morning.”

If you are a night owl that struggles to wake up early, you can start sleeping earlier by ensuring your bedroom is free of distractions, avoiding evening caffeine, keeping lights and electronics to a minimum in the evening (or dimming screens, setting them to “night shift mode”), and sticking to consistent wake times even on the weekends. A dose of bright morning light right after getting up will also help your brain to wake up and start the body’s machinery – don’t stare directly into the sun, as this will hurt your eyes, but you should face the sun (or a light box).

Or if you are an early bird that yawns through the evening shift, you could try gradually shifting your sleep and wake times forward, turn on bright lights in the evening when you need to be alert, and take naps if needed to ensure you are getting enough rest.

A recent Salk Institute study identified a master gene responsible for sleep and wake cycles, the Lhx1 gene, that raises the possibility of “resetting” sleep cycles for shift workers or those with jetlag. Discoveries like this one could open the possibility of solving sleep problems and adjusting rhythms, which could be interesting in the future.

Share: Do you find the personality traits for you sleep phenotype accurate? Anything surprise you?

This article is for informational purposes and should not replace advice from your doctor or other medical professional.