When we think about improving our health and the quality of our lives, we think a lot about what
to do and how
to do it. How to sleep better
, what to eat, what to say when we’re pitching an idea in a meeting, how to work through conflicts with our partners or our kids… but we don’t think nearly enough about when
You’ve probably noticed, without ever giving it much real thought, that all sorts of daily activities come more easily to you at specific times of the day. You feel sleepy and ready for bed at roughly the same time every evening. You get hungry at certain times, and are primed for exercise at others. During some periods of the day, you’re able to focus your mind like a laser, while at other times, your mind easily wanders. You’re in the mood for physical intimacy at certain times of day, and less so at others.
Why? Because your body has a daily biological rhythm that influences sleep and nearly everything you do during the day. How
are important questions, but from a biological standpoint, it’s the when
that is the real secret to sleeping better and living healthier, happier, more productive lives.
Our biological rhythms, AKA circadian rhythms
, operate on a roughly 24-hour schedule, led by a precise timekeeper in the brain—our master biological clock, also known as the circadian pacemaker. Our master clocks take cues from light and darkness, information that’s transported from our eyes to the clock center of our brain. And this powerful inner clock directs rhythms like a band leader leads an orchestra.
Like the individual instruments, daily rhythms for sleep, hunger, metabolism, immunity
, cognition, desire, creativity, sociability and nearly all of your body’s physiological activity rise and fall throughout the 24-hour day, each playing their part in the orchestra that is your body’s daily functioning.
When this amazing biological orchestra of circadian rhythms is playing in sync—and when we know how to use these circadian rhythms to our advantage—we can optimize our daily lives, becoming better rested, healthier, more energized and productive, more successful and fulfilled in our relationships and careers.
Too often, however, we live our lives out of sync with our biological clocks. For most of human history, our ancestors lived in sync with the solar night and day, their circadian clocks in constant, natural response to the presence of sunlight and darkness. Modern life operates differently. We adopt schedules for sleeping, eating and productivity that may adhere to society’s timetable, but don’t align with our own natural rhythms. Circadian misalignment
is tremendously common in our perpetually lighted, 24-7 digital world. And circadian misalignment has profound negative consequences for our sleep
, our physical and emotional well being, our health, happiness and longevity
The good news? Sleeping and living in sync with the rhythms of our biology is entirely within reach. It doesn’t require going to bed when the sun goes down. And it all starts with knowing your chronotype.
Here’s where things get really interesting. Because not everyone’s circadian clock runs at exactly the same pace. Slight differences in our individual clocks lead to different biologically driven preferences for the timing of our daily activities and endeavors. These differences in circadian timing explain why you wake before your alarm, while your partner hits the snooze button nine times, or why you’re up for a late dinner and drinks, while your best friend would rather grab an early bite and head home to an early bedtime.
As a clinical psychologist board-certified in sleep medicine, I’ve devoted much of my professional life to studying and learning the real-life lessons of our circadian rhythms. The study of circadian rhythms is known as chronobiology (chrono, from the Greek word chronos
, means “time”). Decades of research in chronobiology has identified different preferences among individuals for the timing of sleep and waking activity, ranging from a morning preference to an evening preference, with some people occupying the middle ground. These variations are known as chronotypes.
In more than two decades of study and clinical practice with patients, I have identified four different chronotypes, each with their own set of preferred timing for sleep and waking activity.
The 4 chronotypes
Take the chronotype quiz to find out yours.
About 15 to 20 percent of us are Lions—the early risers of the world. Lions are optimistic, goal-oriented, and bring a natural discipline to their daily routines, including their sleep habits. These are the Eagle Scouts, CEOs, power brokers and alpha moms. Lions are leaders and go-getters.
Lions are generally good sleepers, with a medium sleep drive. I rarely meet a Lion who struggles much to stick to a regular, early bedtime. Lions are often the subject of some envy, for their industriousness and the seeming ease with which they stick to their routines. Their tendency toward consistency and moderation in their sleep routines and their daily habits shows in their overall health picture: research shows morning types with early bedtimes have a lower risk for cardiovascular disease, less obesity and may have lower risks for mental health disorders
, including depression, anxiety and others. Lions leap into their days with a lot of vigor—the first half of the waking day is when Lions are at their most productive.
This is the most common chronotype—about 50 percent of the adult population are Bears. Bears’ daily circadian timing most closely follows the sun. Bears biologically start to kick into gear at dawn, and naturally begin to wind down at sunset. Because it’s the most common chronotype, Bear time has a dominant influence over our broader social time.
The standard 6 p.m. dinner hour? That’s when Bears are ready for their evening meal. Your favorite TV shows that start at 10 p.m.? That’s exactly when Bears are ready to wind down for the night—but not quite ready for bed. To a large degree, all chronotypes are asked to live on Bear time, because that’s what society—with its Bear majority—has adopted as the norm. Bears are most alert and productive during the middle of the day, from late morning through early afternoon.
Bears are social and outgoing, amiable and fun-loving. They have a high sleep drive and tend to sleep deeply, but often go without enough sleep to meet their high needs for sleep. Bears are susceptible to what’s known as social jet lag—losing sleep to a schedule that doesn’t give them enough time to get the sleep they need, every night. For example, Bears are prone to under-sleeping during the workweek and seeking out make up sleep on the weekends. This see-sawing can throw Bears’ circadian clocks perpetually out of sync. Bears can have a hard time sticking to a consistent, daily exercise schedule. (They’re not wild about schedules in general.) And that contributes to both their sleep deprivation and to the extra weight that many Bears carry, especially around their midsection.
About 15 to 20 percent of adults are Wolves. Wolves are night-dwellers, the folks who have to drag themselves out of bed before 9 a.m. and don’t start feeling really tired until midnight or so. With their strong preference for evening hours, Wolves tend to struggle the most adhering to the standard schedule that society dictates. Things like work and school get going too early, and social fun ends too soon for these nocturnal types. Wolves are creative, impulsive, and emotionally intense. They’re naturally inclined toward risk taking and seeking out new experiences—they’d just like to have those endeavors happen after noontime, if possible. Wolves have peaks of productivity in the late morning and again in the late evening.
Wolves have a medium sleep drive and generally function at their best with around 7 hours of sleep—but that’s hard for many Wolves to get because their biological rhythm is so at odds with society’s timetable for daily life. Wolves are at high risk for chronic social jet lag
and insufficient sleep, with consequences for their mental and physical health. Research shows evening chronotypes are at greater risk for chronic diseases including cardiovascular illness and diabetes
, as well as depression.
Roughly 10 percent of the population are Dolphins. Dolphins are a distinctly different chronotype from the other three, with circadian biology that is flipped upside down. Dolphins are “wired and tired” types—chronically tired during the day and wired with restless, nervous energy at night. In contrast to other chronotypes, Dolphins’ brain activity lights up at night. Dolphins are light and restless sleepers with a low sleep drive. Dolphins tend to wake frequently during the night, so much that Dolphins’ nighttime sleep can feel more like a series of unsatisfying naps. Intelligent, cautious, detail oriented and often anxious, Dolphins find it hard to relax at night. Their minds are active in the evening, with often racing thoughts, and they feel physically keyed up.
There are biological reasons for all this nighttime agitation in Dolphins. Unlike other chronotypes, Dolphins’ blood pressure and cortisol levels rise in the evening, which leaves them in a state of physiological arousal at bedtime
. Come morning, when other chronotypes are experiencing elevations to blood pressure and cortisol that are fueling their morning alertness, Dolphins’ levels are plummeting. Symptoms of chronic insomnia—prolonged trouble falling and staying asleep, waking often, waking early, and feeling deeply fatigued throughout the day—are commonplace among Dolphins. Increasing their energy during the early part of the day, and learning to relax their minds at night, are keys to improving Dolphins’ nighttime sleep and daytime performance.
Can chronotypes change?
Chronotypes are genetically determined, hard-wired to our biology from our DNA. But they do change over our lifetimes. As young children, we start life as Lions, before becoming Wolves as teens. In young adulthood, usually around mid-twenties, we settle into one of the four chronotypes for the bulk of our adult lives. In older age, chronotypes sometimes change.
Some people have a hybrid chronotype, combining characteristics of multiple chronotypes. Here’s a guide to understanding and navigating a hybrid chronotype
. And here’s where you can read about managing the sleep and productivity challenges facing each chronotype during the coronavirus
How can I benefit from knowing my chronotype?
Here are two examples of how applying your chronotype to daily life can change—and improve—your habits. In my book, The Power of When
, I discuss the application of your chronotype to every aspect of daily living, from work to relationships to diet and exercise and managing illness.
1. Physical intimacy
Want to make sex more exciting, invigorating and frequent? Pay attention to your circadian timing. Most couples fall into a pattern of having sex at bedtime, when it’s convenient—according to one survey, the convenience of bedtime accounted for 72 percent of sexual encounters. If we take circadian timing into account, bedtime is the worst time for sex, for all chronotypes. Partners are tired from their long days. The hormones that fuel sexual desire—especially testosterone—are at their lowest point of the day. Meanwhile, the body’s bio rhythms are calling for sleep.
The best time for sex? According to bio time, it’s the morning. This is when the sex-related hormones are at their daily high, for both men and women, so the desire rhythm is peaking. Creativity is also at a peak during these slightly groggy morning hours, which can make sex more playful and fun. Plus, you get great physiological and psychological benefits from sex that you can reap the benefits of, all day long.
2. Drinking coffee
Here’s some major, myth-shattering information: drinking coffee
first thing in the morning doesn’t shake off the cobwebs of sleep. It won’t make you more alert. It doesn’t give you a surge of energy.
Most caffeine drinkers feel deeply reliant on that morning cup of coffee. But your circadian system already has your early morning alertness boost. First thing in the morning, several stimulant hormones—including cortisol, insulin and adrenaline—are rising sharply. These hormones fluctuate throughout the day and night according to the body’s circadian rhythms. And the initial, waking boost of cortisol and other hormones is so powerful, and renders caffeine useless, in terms of elevating alertness.
It may taste great, but drinking a cup of coffee first thing in the morning does nothing more than increase your tolerance for caffeine
, so you’ll need more overall in order to experience its stimulating effects, regardless of the time of day.
The key to using caffeine effectively is to time your coffee consumption for when cortisol levels are low. Under these conditions, caffeine will trigger an adrenaline boost, helping you feel more alert just when you need it. The timing of cortisol shifts varies from chronotype to chronotype.
The best times for caffeine are:
- Dolphin: 8:30-11 a.m. and 1-2 p.m.
- Lion: 8-10 a.m. and 2-4 p.m.
- Bear: 9:30-11:30 a.m. and 1:30-3:30 p.m.
- Wolf: 12-2 p.m.
These caffeine windows aren’t a license to go crazy with caffeine. Keep consumption moderate to avoid caffeine jitters and fatigue. To protect nightly sleep
, all chronotypes should consume their caffeine for the day by midafternoon.