This article will define what a chronotype is, detail the categories of chronotypes, and explain why chronotypes differ between people. It will then wrap up with a discussion of chronotypes’ impact on sleep.
What Is a Chronotype?
Chronotype also influences how alert or tired you feel at various times throughout the day and impacts when you’ll be most productive during your waking hours. Chronotype is related to circadian rhythm. Circadian rhythm coordinates your body’s physiological processes, including the sleep-wake cycle, into a 24-hour sequence. Your chronotype, also known as a circadian preference or circadian typology, is your innate inclination to sleep or wake up based on your circadian rhythm. Research has shown that chronotype changes throughout the lifecycle. Kindergarten children prefer to wake up early, while adolescents prefer waking up and going to sleep later in the day, a phenomenon that increases throughout the teen years and peaks around the age of 19. Chronotype then shifts back to a preference for waking up earlier throughout adulthood. Men generally have later chronotypes than women before the age of 40, but after age 40 have earlier chronotypes.
Chronotype Categories
Researchers have divided chronotype into three categories:
Morningness, or the preference for waking up and going to bed earlier than most people.Eveningness, or the preference for waking up and going to bed later than most people.Intermediate, which falls somewhere in between morningness and eveningness.
Even though both sleep scholars and the general population tend to emphasize morningness and eveningness when describing sleep timing preferences, the reality is that chronotypes are distributed nearly evenly along a spectrum. As a result, most people fall somewhere between the extremes of morningness and eveningness. Furthermore, a number of scholars have suggested there’s a fourth chronotype:
Bimodal, or people who display some aspects of morningness and some aspects of eveningness.
Discovering Your Chronotype
You may already know you wake up before the sun rises or prefer to go to bed after most everyone else is asleep, but if you’re not sure what chronotype category you fit into and want to find out, you can take the Morningness-Eveningness Questionnaire. This is the measure most often used by scientists. It is available either online with automated results that come with personalized feedback or in a printable format that explains how to interpret the results for yourself. One of the most popular chronotype assessments is the chronotype quiz by clinical psychologist and sleep expert Michael Breus, who has broken chronotype down into four categories based on animals, including:
Lion — which roughly correlates to morningnessWolf — which roughly correlates to eveningnessBear — which roughly correlates to intermediate types. According to Breus, this type is more productive before noon and decreases in energy in the late afternoon.Dolphin — which roughly correlates to bimodal types. Breus says these individuals are most productive between 10 a.m. and 2 p.m.
While Breus’ quiz is fun and easy to take, it’s important to know that there’s no evidence to suggest it has been validated or peer-reviewed, the gold standards for confirming that a questionnaire actually measures what it claims to.
Why Do People Have Different Chronotypes?
Some scholars propose that the variations in chronotype between individuals is a product of human evolution. A 2017 investigation of a hunter-gatherer tribe in Tanzania demonstrated that over 20 days, different individuals took turns sleeping while others were awake. This asynchronous sleep-wake pattern was connected to variations in chronotype. Based on these findings, the researchers suggested that different chronotypes are a product of natural selection, ensuring certain people stayed awake to keep watch at various times throughout the night to protect the group against vulnerabilities to predators and other dangers during sleep.
How Do Chronotypes Affect Sleep?
Adequate sleep is essential for healthy functioning. Therefore, it’s valuable to know how our chronotype might impact our sleep. Chronotype can effect how individuals interact with their environment, especially when it comes to the social parameters of work and school hours or other scheduled activities. This can be especially problematic for people with an evening chronotype. A single hour of social jetlag can increase cardiovascular disease risk by 11%, so evening types’ predilection toward social jetlag not only disrupts their sleep schedule, but it can also impact their overall health. In addition, those with later chronotypes have a tendency to have poorer sleep quality. Meanwhile, those with morning chronotypes appear to adjust more quickly to shifts in the duration, timing, and quality of their sleep than evening chronotypes. On the other hand, morning chronotypes may have difficulty staying up late to participate in social activities.
A Word From Verywell
If you have a later chronotype and work at an office that adheres to an earlier schedule, it might be beneficial to speak to your boss about your particular needs. Morning chronotypes will thrive on a standard office-day work schedule, but evening chronotypes are likely to be more productive if they start and end their workday later. In fact, one study found that evening chronotypes who worked from home during the COVID-19 pandemic and therefore had the flexibility to get up and go to bed later in the day no longer experienced issues with sleep. This indicates that if evening types were able to work on a schedule that lined up with their chronotype, their sleep quality and quantity would improve.
