There have been multiple naming and approaches to splitting and categorising the sleepers, but the most accepted categorisations are morning type (also known as morning larks or lion); intermediate type (also known as hummingbirds or bear) and evening type (also known as evening owl or wolf). Moreover, Dr Michael Breus has introduced a 4th type which he refers to as dolphins or “sensitive sleepers”. 

Rather than challenging your body's natural rhythm with an ineffective sleep routine, it's better to work with your Chronotype. Knowing your Chronotype is the first step in understanding its benefits and drawbacks. 

What is the difference between Chronotype and Circadian Rhythm?

The circadian rhythm, which regulates the day-to-day sleep-wake cycle and produces melatonin in response to environmental factors like light and temperature, is intimately linked to sleep Chronotype. While the circadian rhythm can be "conditioned" by sticking to a rigorous schedule, the underlying Chronotype remains constant.

Total sleep time is unaffected by Chronotype. However, we have to consider the social factor for an objective analysis. Indeed, our society has very morning schedules, which make the lives of the 'early birds' simpler than those with a more nocturnal chronotype. For example, consider the start time of classes at school or university. While a morning chronotype can get all the necessary hours of sleep to feel rested, a night chronotype will be forced to give up a few hours of rest. As a result, night owls have historically had a more challenging time adjusting to traditional work patterns.

Sleep experts believe it is difficult to modify your Chronotype intentionally. However, it does change with age and can be adjusted with proper steps.

What affects your Chronotype?

Genetics, age, sex and other variables can all influence a person's Chronotype. Due to differences in daylight hours, some researchers have found that Chronotype may differ depending on geographical location. People in the same time zone can experience sunrise up to 1 to 1.5 hours apart, which affects the synchronisation of their internal clock to the external clues, better known as zeitgebers, for example, the sun.

Women tend to have an earlier Chronotype than males, while some research shows that this difference fades around 50. Likely, gender differences are merely a result of societal issues like family chores, career advancement, and retirement, which generally follow different patterns for men and women. Beyond genetics and the time zones, your Chronotype also changes over your lifetime:

1. Your Chronotype starts with being more morning during your childhood and gradually becoming a late type during your teenage years (this explains why it is so common for teenagers to sleep later and sleep in throughout the morning hours).
   There’s also a gender difference where females reach their peak in lateness at 19.5yrs old while for men at 21, it takes a few years for the Chronotype to shift phase and become more intermediate. 
2. While for most of our adulthood people tend to be intermediate types, they gradually become more early types and need to sleep and naturally wake up earlier similar to how it all started in childhood.

What are the 4 types of Chronotype?

• The morning chronotype represented by a lion,

• The intermediate type represented by a bear;

• The night chronotype represented by a wolf.

• Dr Breus included in his list a fourth type, the so-called dolphin type.

Each Chronotype is roughly based on the sleep cycles and behaviours of the related animal, so let's have a look to see which Chronotype you most closely resemble.

Morning Chronotype 

15-20% of the population is a morning type. In the categorisation made by Dr Breus, credited with consolidating knowledge on these topics, this chronotype is represented with a lion. Morning types wake up earlier and reach their cognitive and energetic peak early in the day. At night, the melatonin (the famous hormone known for its importance for sleep regulation) is secreted earlier than other chronotypes. Conversely, in the morning, cortisol levels (enabling your body to wake up and be alert) are also sent around earlier than in the rest of the chronotypes. This is the reason why you become tired in the evening more quickly. While as a morning person, you are less flexible in terms of waking hours, and shift work would be a nightmare, it is relatively easy for you to function well when following the typical social and work schedule. Decades of studies have shown that morning people tend to lead healthier lifestyles by following more regular meal times, physical exercise and keeping a lower intake of psychostimulants (coke, coffee, nicotine, alcohol).

It is essential to know the right time for you to get on with your daily activities. As the melatonin levels start to drop earlier than anyone else, you are early to rise. Use these morning hours for a big breakfast and exercise before you sit down to work and tackle all your decision-making and high-focus needed tasks! Use your after-lunch hours for easier tasks and let the creativity flow if needed! As a morning bird your melatonin levels kick in earlier on, thus when the evening comes, one of the downsides might be the potentially missing out on social activities that tend to take part until late in the evening. One way to get an energy kick is to exercise and have your dinner in the earlier evening hours for the last boost before winding down and going to bed earlier in the night.

Intermediate Chronotype

Ca 60% of the population is an intermediate type. This chronotype is also known as the Bear, according to the categorisation made by Dr Breus.

Intermediate types are neither morning nor evening types, and the inner clock is aligned with the astronomical day - following dawn and dusk. As an intermediate type, this makes it easy for you to follow the typical work schedule. To increase the morning alertness, we suggest starting the day off with exercise and a big breakfast, while avoiding carbs. The morning exercise will boost your awakening and you can easily slide into the morning hours of higher focus work until lunchtime. To avoid the afternoon slump, you can take a quick power nap or go for a walk to get your body moving and the lunch metabolised better. You can space the afternoon for focus tasks followed by the ones that require more interaction with others such as meetings, and calls.

Finish the day with a light dinner and avoid late-night snacking - tends to happen for intermediate types. Find a way to relax away from blue light-emitting screens and emotional arousals (media content) before winding down for bed. 

Evening Chronotype

The Wolf generally represents the evening type. It means that you would naturally feel sleepy later in the night and sleep later into the morning hours - this may be due to a later onset of cortisol secretion. Around 15% of the population is an evening type. Based on your chronotype, your attention increases from the morning to the mid-day and afternoon, and you tend to also be more creative in the evening. Late-type athletes have their peak physical performance in the evening so that an after-work workout would be optimal timing for you. 

While your inner clock is linked to your DNA, it is not easy for you to become a morning person. However, you can take small steps to entrain it to an earlier bed and wake-up time. Our sleep experts have a few suggestions for organising your day and awakening your best. When you need to wake up a few hours ahead of your inner clock, we suggest exposing yourself to natural light in the morning. Natural light is x50 stronger than office light in the morning and sends signals to your suprachiasmatic nucleus (SCN) located in the middle of your brain that it's 'go time' - so make sure to open the blinds, go on your balcony or even a walk! Alternatively, you can use a chrono lamp for ca. 15min in the morning. As your focus increases in the afternoon, plan your day so that more demanding tasks are scheduled for the afternoon. Schedule your physical activity in the late afternoon/early evening hours and avoid late-night snacking as well as alcohol. Finish the day off by seizing your good evening mood with loved ones before you wind down for bed.

Light sleepers/sleep strugglers 

Dr. Breus, in his highly acknowledged book 'The Power of When', describes the existence of a fourth rare chronotype, which he identifies as the dolphin. This category represents those who have difficulty falling asleep and are rarely able to achieve a night of total rest. Actual dolphins, the insomniacs of the sea, sleep with half of their brain turned on at a time, which helps them keep vigilant and wary of predators.

Dolphin Chronotypes normally fall asleep because their bodies require it, not because they want to do so. Only 10% of the population is considered dolphins.

Can our Chronotype become disrupted?

Sometimes our chrono clocks can become disrupted, or altered, due to lifestyle changes or sleep disorders. Here are the most common factors for a change in sleep Chronotype:

• Social jetlag and shift work
  
• Circadian rhythm sleep disorders such as ASPD (Advanced Sleep Phase Disorder). This is a genetic mutation where people can sleep at 7-8pm and wake up at 4am. This makes it very hard to keep up to a regular schedule which is typical societal norms. DSPD (delayed sleep phase disorder) on the other hand, is a more frequent condition where people can sleep 3 hours later than the average sleeper and also wake up later.
  
• Freerunning - This can happen to people with ocular disorders that have no connection from their retina to the SCN (Suprachiasmatic Nucleus, the inner clock setter, situated in the middle of the brain).
  This means that people's endogenous cycles start free running at 24 hours and 10 minutes. So after 1 week they are already behind schedule by an hour compared to others that can be affected by light exposure and have their inner clock entrained to the external environment.

The benefits of knowing your Chronotype

Knowing your Chronotype can help you understand your sleep and waking cycles, as well as your peak production periods. The following are some of the advantages:

• It assists you in recognising when you are likely to go to sleep. According to studies, evening Chronotypes have sleep habits that are 2 to 3 hours later than morning Chronotypes.
  
• Knowing your Chronotype might also assist you in keeping track of your eating habits. The relationship between Chronotype, nutrition, and cardiometabolic health was investigated in one study. They discovered that an evening Chronotype, such as wolves, had a lower intake of fruits and vegetables and an increased intake of caffeinated drinks, alcoholic, sugary, and caffeinated beverages, as well as a greater fat intake.

There's more: Here at Emma, we wanted to test different kinds of correlations between the chronotype and other elements of people's lives. Through our study, conducted in January 2022, we were able to verify how the type of chronotype correlates with the annual salary of study participants.

We observed that morning chronotypes tend to have a higher annual salary than those with an afternoon chronotype. Sleep consistency also seems to be related to chronotype. As many as 66% of participants with a morning chronotype stated a consistent sleep routine, compared to 48% of those with an evening chronotype.

Another element that differentiates the different chronotypes is the time spent outdoors. As a matter of fact, our data shows that, on average, morning chronotypes prefer to spend more time outdoors, while night chronotypes tend to spend more of their lives indoors or, in general, in enclosed places.