Bringing up the topic of 'the best time to sleep' often leads to an emotionally charged discussion. Given the day-oriented world we live in, early risers usually have the upper hand in these conversations.
Even the nickname 'early bird' references the old adage "the early bird catches the worm," which suggests a link between waking early, productivity, and success.
On the other hand, 'night owls' can be judged more negatively by society. Going to bed in the early hours of the morning and rising later in the day is more likely to be associated with laziness and poor discipline. Given the value attached to rising early, many try to change their sleep habits to follow the morning lark pattern.
However, research shows that it might not be up to us to decide whether we are morning or evening people. Our natural sleep orientation may be largely determined by our genes, and going against it may be counter-productive.
Around 20,000 nerve cells within a section of the brain called the suprachiasmatic nucleus control our body's internal sleep-wake cycle — our 'circadian rhythm.'
This inner rhythm is what makes us naturally sleepy or awake by a certain time, even if we don't look at the clock.
We are all born with our own circadian rhythm, so one person might identify as more of a "morning person" and another as an "evening person." These circadian preferences, which fall along a continuum, are called "chronotypes."
Many biological and environmental factors influence the timing of your circadian rhythm. However, recently it's become apparent that genes play a big role in determining if you're a morning or evening person.
In the past, it was assumed that around 24 genes controlled your chronotype. But in fact, a more recent 2019 study¹ by researchers from the University of Exeter and Massachusetts General Hospital identified 350+ different gene locations involved in circadian preferences.
They analyzed the genetics of almost 700,000 participants and took self-reported sleep measurements along with activity data from wristband monitors. Those that carried more "morning genes" woke up 25 minutes earlier on average compared to those with fewer of these genes.
While chronotype can change as we age (many trends towards the early-bird pattern), studies have shown that between one-fifth to half of our chronotype is determined at birth by our genes.
What accounts for the rest of that proportion? A large amount of it comes down to environmental factors.
One of the most important external cues influencing our sleep-wake cycle is light. When we are exposed to light, it is received and processed by nerves in the eye that are connected to the brain. This signals our body to stay alert.
Conversely, darkness prompts the body to start producing the melatonin hormone, which prepares it for rest.
The interesting thing is seeing how environment and genetics interact to result in various chronotypes. For example, variations were found in the genes that controlled the retina (part of the eye that processes light) for various chronotypes.
This is why chronotherapies (like melatonin pills or lightboxes) that help adjust circadian rhythm have varying effects on people of different underlying chronotypes.
Interestingly, your circadian rhythm isn’t just for signaling sleep and wake times. It’s closely linked to many other biological processes that affect our overall health and well-being.
Almost every organ and the bodily system go through changes throughout the day that are in sync with our circadian rhythm. This includes our hormone levels, body temperature, and metabolism.
Cardiovascular measures like heart rate, electrocardiogram (ECG) readings, and blood pressure also vary throughout the day in sync with our internal clock. At night, there's usually a lowering of heart rate and blood pressure.
The liver, which controls many metabolic processes for storing and releasing energy, also follows the circadian rhythm. After a meal, our liver usually tries to store nutrients from the food we've just eaten. At night while we're asleep, the liver metabolizes these stored nutrients for energy to keep our body's essential functions running.
When we don't work with our internal circadian rhythm, it doesn't just disrupt our quality of rest. It also interrupts a multitude of other biological processes in our bodies that can increase our risk of developing illnesses.
For example, if you suddenly decide to eat in the middle of the night, your body can get confused about whether it should be storing or releasing nutrients. It can also disrupt the insulin hormone, which regulates blood sugar levels.
This is why shift workers who work irregular hours are at an increased risk of metabolic syndrome, which includes a cluster of conditions such as:
High blood pressure
High blood triglycerides
It also ultimately increases a person's risk of diseases such as diabetes and heart disease in the long term.
Researchers have been looking at how early school start times are at odds with the internal clocks of teenagers. As we approach puberty, there is a biological shift to a later bedtime. Getting teens to adhere to 8 AM school start times may be against their innate body schedule, which can result in chronic sleep deprivation.
It is estimated that 73%² of high school students aren't getting enough sleep at night, and this is impacting various areas of their functioning — including their academic performance and mental health.
A simple solution could be to start school at a later time. When a UK high school experimented³ with different starting times (8:50 AM versus 10 AM) across a four-year period, they found favorable outcomes when beginning later, with fewer reported sick days and improved academic performance.
Research tells us that we can't choose when it's the best time for us to sleep. But are night owls really at a disadvantage when it comes to health and productivity? So far, the evidence seems to favor early birds.
The researchers who revealed the underlying genetic factors determining chronotype also cross-referenced it with genes that influence mental health. They discovered that ‘early bird’ genes were associated with a lower risk of schizophrenia and depression along with improved subjective well-being. A separate 2012 study⁴ also reported that morning people are more likely to report higher levels of positivity compared to evening people.
In terms of physical health, night owls are also at higher risk of developing obesity, heart disease, and diabetes. They are also more likely to engage in unhealthy lifestyle behaviors like smoking, binge drinking, and engaging in less physical activity.
However, scientific research⁵ has demonstrated some perks of being a night owl. One study found that adolescents who slept later were more likely to score higher on intelligence tests. Others suggest they're able to remain alert for longer periods during the day and come up with more creative solutions to problems.
On the surface, an earlier sleep schedule may seem like a healthier choice. However, the issue might not just be those night owls have an innate disadvantage. We need to take into account the fact that we live in a society that favors day-oriented people, with work and daily amenities all adjusted to fit the nine-to-five schedule.
An office worker with a later chronotype who goes to sleep at 3 AM may have no choice but to drag themselves out of bed four hours later. In the long term, this can lead to sleep deprivation and the many health issues associated with it — including lower mood and metabolic syndrome.
Sleep researcher Dr. Elise Facer-Childs describes this struggle for night owls to match regular working hours as a form of daily jet lag. Not surprisingly, she and her team of researchers at the University of Birmingham found that night owls experience similar effects to what we see in travelers with jet lag.
Those with late chronotypes had lower brain connectivity throughout the day (8 AM to 8 PM) in areas that control performance and sleepiness when compared to early birds.
Given that a big part of sleep-timing preference is determined by genes, societal perceptions of night owls need to change. The innate drive to sleep later is not due to laziness or lack of discipline — it is biology.
Productivity gurus often tout quick-fix life hacks for waking up early to get more done in a day. But the reality is that this approach isn't for everyone. Night owls who attempt to model these cookie-cutter suggestions are likely to fail or struggle to maintain the habit. It can ultimately leave them with an unnecessary sense of failure or shame about something that's out of their control.
There needs to be more aware that one chronotype isn't necessarily better than the other. People should be aiming to live in sync with their internal body clock rather than the clock dictated by others.
Experts like Facer-Childs suggest that the world should allow more flexibility in starting the day a little later to accommodate night owls. In the long run, it might help to reduce many of the health and well-being issues associated with delayed chronotypes.
"If, as a society, we could be more flexible about how we manage time, we could go a long way towards maximizing productivity and minimizing health risks," said Facer-Childs in an interview with Science Daily⁶.
If you're wondering how to tell what your chronotype is and how you can sync with it, here are some tips:
To get an idea of your chronotype, try spending a day free of any work and social commitments, and tune into when you naturally fall asleep and wake up.
There are also online questionnaires that you can fill in to understand yourself better. One of the most popular ones is the Morningness-Eveningness Questionnaire (MEQ)⁷. It has five sleep types ranging from definite morning to definite evening.
However, Dr. Michael J. Breus, a clinical psychologist and sleep expert, has challenged the narrow focus of the MEQ as it doesn't take into account sleep drive. He's gone further to specify four different chronotypes based on the sleep patterns of mammals⁸:
The Lion: The typical early bird who wakes early and is freshest in the mornings. They usually don't have an issue sticking with a regular, early bedtime.
The Bear: They're the most flexible of the four chronotypes and follow the sun's schedule (even though they have a high sleep drive). This also means that they can be at risk of irregular sleep patterns to accommodate social or work responsibilities.
The Wolf: Your typical night owl who struggles to get out of bed in the morning. Their performance tends to peak in the late morning and again towards the end of the day.
The Dolphin: These restless sleepers are just like real dolphins and can remain alert while sleeping. As a result, many struggles with insomnia.
Once you've got an idea of your chronotype, try to line up your schedule with when your body requires rest or activity. For lions, productivity is optimal in the mornings.
On the other hand, wolves may want to try ramping up activities towards the end of the day or starting the day later if the work environment allows for it.
But whatever your chronotype, it still helps to practice good sleep hygiene to get enough total hours of rest each day. This can include:
Have consistent sleep and wake timings even on the weekends or holidays
Avoid using electronic devices before bed — the light emission disrupts your circadian rhythm
If you want to slightly shift your sleep schedule, do it gradually (15-30min increments every few days)
Avoid eating too much or drinking caffeine too close to bedtime
Stay active and exercise regularly
Ensure that your bedroom is conducive to sleep (dark, relaxing, and a comfortable temperature)
Morning larks and night owls all deserve quality daily sleep. It's just that it might take place at different times of the day for different people.
Night owls are often labeled as lazy, while early birds tend to be seen as more productive. However, research has shown that rather than be down to a personality trait, our sleep preferences are driven by genetics.
Getting up and going to sleep at times contrary to your circadian rhythms over a long period can negatively affect your health. Follow our tips for maintaining good sleep hygiene to give yourself the best chance of not letting a lack of sleep affect your physical and mental health and well-being.
Automated morningness-eveningness questionnaire (AutoMEQ) | Center for Environmental Therapeutics
The four chronotypes: Which one are you? | Psychology Today
Circadian rhythms | NIH: National Institute of General Medical Sciences
Understanding the genes that make our circadian clocks tick | The Conversation
Why late-night eating disrupts glucose metabolism | Dr. Satchin Panda | Found My Fitness
Metabolic syndrome | Better Health Channel
Chronotypes | Sleep Foundation
Tips for better sleep | Centers for Disease Control and Prevention
Morning or night person? It depends on many more genes than we thought | The Conversation
Dawn Teh is a health writer and former psychologist who enjoys exploring topics about the mind, body, and understanding what helps humans thrive.
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