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Circadian Rhythm is Set by Cues Inside Our Bodies
There are times when you know it's right to sleep and you know that there are times of the day that your mood's a little better than others. And you know that there's a time of day when you're hungry and there's a time when you're not. And there's a time when you emotionally go up and down, and it turns out that your body, our bodies, have a circadian rhythm.
That means throughout the day, some things are more or less on and some things are more or less off. And this is called the circadian rhythm, and it turns out there are controls of our circadian rhythm that don't have anything to do with necessarily when the last time was you ate or what the lights are outside although there are social cues to how you decide when you're going to eat and sleep and be happy and take your tests. But in general, your circadian rhythm is set by cues inside your body.
Are You a Morning Lark or Night Owl?
Now, with us in the studio today is Dr. Chris Jones. Dr. Jones is an MD and a PhD, and he studies when creatures do stuff. He's a chronobiologist. He studies when creatures do stuff and why they might do those things when they do.
Dr. K. Jones: Can I call you, Chris?
Dr. C. Jones: Oh, all right.
Dr. K. Jones: I can call you Chris, as long as they don't call you late for dinner, right? And in the interest of full disclosure, Dr. Chris Jones has lived with my chronotype for over 45 years. So he has a lot to say about chronotypes, and he can speak up about mine if he ever wanted to. So welcome to the studio. Now, we're going to ask Dr. Jones or Chris, Chris, how would you define chronotype?
Dr. C. Jones: Basically, there are two obvious chronotypes. One is the so-called morning lark, people who wake up very early and they're very happy when they wake up early. And then there are night people who don't fall asleep until sometimes well after midnight, 2:00 or 3:00 in the morning, and we call those people night owls.
Dr. K. Jones: So how is your chronotype determined, and are you born with it?
Dr. C. Jones: Yes, definitely. We think this is a genetic predilection to be either a very morning or very night person.
Dr. K. Jones: So, certainly, there are mutations that make people morning people or evening people, but in fact, all of our genes work together to fine tune our chronotype. So if you were to look at people, there are some very few really morning people, and there are some very few really late people, but then there are sort of morning people and there are sort of evening people, and there are a bunch of people in the middle. There's a bell-shaped curve of times that people like to go to sleep. So does your chronotype change as you go through life?
Dr. C. Jones: Yes, absolutely. The adolescent period is a time when we become later and later and later sleep onset people. In other words, sleep phase delay, and every parent of an adolescent knows that their kid is wide awake at midnight, who knows what they're doing out on the town. And even in very rural circumstances, like the jungles of Central America, sociologists know that the moms and dads in the jungle have no idea where their children are in the dark at night and what they're up to.
Dr. K. Jones: But they do know that they kind of stay up late when everybody else is sleeping and then they wake up late. And we know from researchers in the Kalahari Bush that the word for teenagers means owners of the shade, meaning they keep sleeping in the shade all day because they've been up all night. And this is part and parcel with being an adolescent is you get to be more of a night person. And then what about later in life?
Dr. C. Jones: Well, some people actually use 20 years old as the end of adolescence because that is the age at which people stop getting more and more of a night person or sleep phase delayed sleep schedule. Later in life, things get more variable, whatever your sleep schedule was in your teens, 20s, and maybe your 30s, you know, we're pretty healthy and our genes are working well, but you get to be my age and you don't sleep quite as deeply and sleep schedule could be a little more variable. So it's like everything else, the older you get, things start to fall apart.
Dr. K. Jones: Don't say that. Well, so older people tend to be a little bit more morning people, but whether it's their biology or just because their joints hurt or it's time to get up because they can't sleep that much more.
Dr. C. Jones: Well, the bladder and the joints are the two biggest complaints that elderly people have about their disruptive sleep. They attribute it to bone and joint pain and the bathroom calling and things like that.
Dr. K. Jones: Oh, the bathroom calls me.
The Planet's Affect on Your Sleep
The planet has its own chronotype, and it changes where you are in the planet. And particularly, in the very upper and lower latitudes, when the days are very, very long in the summer and the nights are very, very long in the winter, there are some serious problems when the planet doesn't want to work with your own chronotype. What happens to people who are living in very northern climes when it's bright all the time, what happens to their mood or their sleep?
Dr. C. Jones: First of all, it's thought that the sleep-wake cycle and a lot of the way our brain works evolved in the deserts of Africa, Equatorial Africa. And then we migrated north into the Scandinavian countries. So the folks who live in the Scandinavian countries may or may not have evolved as much as they would have liked to those northern climes. But basically, it's as you said, there are months in the year where it's dark for most of the 24-hour day-night cycle.
Dr. K. Jones: And during the time that it's light people get a little manic when it's light all the time. There's a famous movie called "Insomnia" with Robin Williams and Robert De Niro, and a detective moving up to Alaska to solve a mystery gets a little crazier and a little crazier because he can't go to sleep. It's easier to kind of huddle in when it's cold and dark, so you tend to sleep a little bit longer in that winter months. People get a little more depressed in the winter months. So the planet has its very own chronotype, but it changes through the year.
What Happens When You Don't Live According to Your Chronotype?
Your circadian rhythm isn't only just about your sleep. It's about your emotional highs and lows. People tend to get a little bit more depressed at night and are sometimes a little bit more activated and positive in the morning. And there's also some evidence that the evening time is time for people who have a tendency toward depression. It's a time when people tend to involute. They tend to look inward a little bit more. In the evening time, they're tired. They have a tendency toward depression.
And so, when you're thinking about having conversations with people that might be important, it's important to know where they are. In the morning, people are often a little bit more activated. Not everyone. Certainly morning people are, they got the get up and go. They're feeling pretty optimistic. I think of all the farmers on the planet who have to get up early and get going and they have to feel like they can get stuff done, and there's some biological cues for this.
But in the evening, before we go to sleep, we tend to be more involuting or turning inward and shutting down a little bit all our activities in the brain. And some people get a little bit more depressed at that time and having conversations that might be important, you have to spend some time understanding where somebody might be in their daytime schedule.
Dr. K. Jones: So you have a certain chronotype, you would like to get up at a certain time, but life isn't always like that.
Dr. C. Jones: Usually, that means the person is sleep-deprived. If you don't have the option of falling asleep when your brain really wants to fall asleep, you probably will not fall asleep. And therefore, you'll be sleep-deprived the next day, and that has profound implications for relationships with other people because you're irritable. It also does not impress the employer because you've been late to work. Whatever your work schedule is, it may or may not work with your circadian rhythm.
Dr. K. Jones: Well, and there's some data that says shift workers or night workers who haven't flipped over completely to working nights have a higher rate of cancer. And this has to do with an important hormone made by the brain and now we know it's made throughout the body called melatonin.
And melatonin seems to have some anti-cancer activity in our own bodies, maybe because it's such a powerful antioxidant melatonin is. And people, particularly women, and we've studied this in nurses is that nurses who spent most of their career working night shifts have significantly higher rates of breast cancer. Melatonin may be acting, perhaps there's an antioxidant effect. It's important not to suppress your melatonin because it's there for a number of reasons, and people who work in bright lights all night long and are trying to sleep during the day may be suppressing their melatonin. And that might be some of the activity that might make women more likely to get certain cancers.
Adolescents who are often taking tests, so when I think about my test taking years, although as a physician, I took tests right up until my 60s, but you take tests and when you take your tests, your intellectual health, so what is the chronotype of your brain? When I think about adolescents who might have to take SAT tests at 8:00 in the morning or they have to go to school at 8:00 in the morning and their brain says they should still be asleep, so your intellectual health, there are times of your day when your brain is really on and you've sat across the table from me, looking at me at 9:30 at night and looked at me and said your computer is shutting down, I can watch it. So there are times when your brain isn't working. What do you do about that?
Dr. C. Jones: Oh, it's really hard to argue with your genetic morningness, eveningness sleeper type. There are some things you can do to nudge it one way or the other, and the most powerful is to fix morning wake-up time with lots of light and fix the evening as very dark, as dark as you can, but that doesn't always work for everybody with a very morning or very evening biological genetic sleep schedule.
Your Chronotype and Intellectual Wellness
There are times when you're feeling really sharp and there are times when you're not so sharp, and actually in some of the web-based chronotype questionnaires, they would ask you as they're trying to figure out whether you're a morning person or a night person, when you feel like your work is most productive, or when you feel like you do best on a test. And people often know this, they know when their brain is the sharpest, and that plays into their chronotype, their intellectual wellness.
Dr. K. Jones: Clearly, if you're doing finances, it's important for you to know when your brain is the sharpest, when does it like doing arithmetic. Now, I love arithmetic and I'm a morning person. So I like to do my finances and think about finances certainly before 2:00 in afternoon. But for couples who might have different chronotypes, our sleep psychologist has a really important quote about when couples should talk about money.
Dr. C. Jones: Absolutely. This is from the experience of Dr. Laura Czajkowski, a psychologist at University of Health Sleep Center for quite some time. And her recommendation, very strong recommendation for people who have insomnia or difficulty getting to sleep, one major factor is to schedule the money discussions before noon. Do not wait until the afternoon. It's too close to the evening bedtime. What you want is to get the real sort of irritating discussions that can arise long before you have to go to sleep.
Dr. K. Jones: And when you're actually interested in solving problems and not interested in going to bed or not going to bed angry with someone, so always do your financial discussions before noon, according to the sleep psychologist. Just that you know, you do your finances when you're cognitively most alert and you don't do your financial discussions with your bed partner after noon.
Spiritual Aspects of Circadian Rhythm
Culturally, around the world, there are some cultures whose religious practice is focused on the rising of the sun and certainly Eastern Indian practices in terms of morning yoga. Yoga is not usually done at 10:00 at night. It's something you do in the morning. And some spiritual practices are morning-based.
In Western culture, we go to church in the mornings, but we tend to pray at night. And everyone has a different way of expressing their spiritual life. But it often is based either on morning or evening. It's not usual that we are expressing our spiritual practice throughout the day, except in some quite observant religious cultures. And I think specifically about many monasteries, which might actually pray seven times a day and their prayer is based on the first thing in the morning, the midday, noontime, afternoon and evening prayers, and then there is a bedtime prayer. And, of course, in Islam, they pray multiple times a day.
However, for many cultures, their spiritual practice may be morning based or evening based. And for people who don't have a particular culture, they may find their own time, which is best for them. And it may be based on their chronotype. It may be based on their social time. It may not be so busy in the morning that moms don't have a minute to think about their spiritual life. And it's something that's done later in the day.
But people who tend to work on their spiritual life tend to do it at about the same time of day. And knowing when that time of day is, recognizing how it's important to you, being able to express it to the members of your family, so that you have a little bit of quiet time to indulge, or it's not an indulgence, it's actually important practice of your spiritual life is going to be important in terms of being able to make sure you have the time to do your own spiritual awareness and connections.
Co-existing with Different Chronotypes
What happens in a household with 2-year-olds and 17-year-olds and 40-year-olds and 75-year-olds? How do you work a house when you've got so many people with different chronotypes either because of their age or because of their biology? How do you get along and do so without disrupting each other's hard-wired biological sleep-wake schedule?
Dr. C. Jones: It's really an exercise in relationships between people. And I hate to say that because I'm a guy, but that's really what has to happen. People have to realize, you know, mom's been up early because she's breastfeeding or she's up late because she's feeding somebody or somebody's screaming. And we know from a brainwave recordings that even a whimpering noise can bring a sleeping mother up very close to wakefulness and sometimes full wakefulness. So now you've got a sleep-deprived mom, and sleep-deprivation is really good at causing irritability.
Dr. K. Jones: Well, that's not personal. You're not talking about this personally, given that I spent so many years as an OB, was chronically sleep deprived for about 35 years. But so your brain works . . . when you're sleeping, your brain actually is working, it's sorting out what's important, it's remembering things that are really critical. So you may wake up at 2:00 and if you're really awake, it's like, oh, I forgot to send someone . . . I need to send someone something. And in the olden days, you wrote it down and when you woke up in the morning, you gave someone a call. But now, we can actually post something at 2:00, even knowing that someone won't get it until they wake up.
It's not uncommon for people to remember something that's important when they wake up at 2:00. And that's a time when your brain has been sorting out what you need to remember and what you don't need to remember. That's when you'll say, "Oh, I'll just send her a text." Now, I don't recommend doing that in the middle of . . . because then you really wake up and then you get very fragmented sleep. So it's better just to roll over, not turn on a bright light screen. Just roll over, write down the note. Just tell yourself to remember it in the morning, because things that you tell yourself before you go to sleep tend to be things that you remember.
Live Your Chronotype for a Healthier, Happier Life
We've been talking for about a half an hour about sleep, wake, your chronotype, circadian rhythms, when you wake up, when you're sad, when you eat, are you a night person or a morning person, and all parts of your life which are affected by your circadian rhythms. And tomorrow is another day. So not living your chronotype has some biological effects. People who do shift work are more likely to gain weight. So people who aren't sleeping well. So increased rates of obesity, increased rates of cancer, increased irritability, difficulties at home, all those can happen when you're not able to live your chronotype.
Do you go to sleep?
Wake up now, get up later
It is in your genes
- E44: The Spiritual Domain of Caffeine
- E43: The Environmental Domain of Caffeine
- E42: The Financial Domain of Caffeine
- E41: The Intellectual Domain of Caffeine
- E40: The Social Domain of Caffeine
- E39: The Emotional Domain of Caffeine
- E38: The Physical Domain of Caffeine
- E37: 7 Domains of Retiring
- E36: 7 Domains of the Heart
- E35: 7 Domains of Book Club