Picture this: You’re about to be offered the job of your dreams. As your prospective boss welcomes you to your new company, she adds, “And of course, we’d want you to attend our daily staff meeting — it’s at 7:30 am in the conference room.” At which point, you quickly reply, “Oh, sorry, that won’t work for me. My biological clock is set so that I function best working on a noon to 9 pm schedule. Is that OK?”
Most people know an answer like this would result in a “don’t call us, we’ll call you” brush-off. In real life, you’d swallow hard and say, “Sure, 7:30 am, looking forward to it!” whether it was true or not. In reality, some of us thrive on early wake-up times, while others find getting up with the birds to be a real burden. Each of us is hard wired to be either a “morning person” or a “night person,” which means our body clocks are set to run on a particular sleep/wake cycle. Scientists call this our chronotype. Basically, chronotypes are divided into three types depending on bedtimes: early, intermediary or late.
A brief online quiz developed by researchers at the University of Munich can help you determine your chronotype. There’s also a simple test that you can do on your own. Craig Canapari, MD, specializes in treating children with sleep and breathing problems at Yale New Haven Children’s Hospital. “To determine your chronotype, you have to figure out your typical “mid-sleep” on free (no work) days (MSF) that is the halfway point between when you go to sleep at night and wake up in the morning. But you have to do this on a night when you can fall asleep naturally and get up naturally, which means not when you’re following a particular schedule. You take the total amount of time you sleep at night and divide it by two. For example, if you find that on those free days you routinely fall asleep around midnight and get up at eight, your chronotype or mid-sleep would be 4 am. That’s your ideal sleep/wake MSF.”
For most people, the most common MSF is between 4-5 am, suggesting that most of us are wired to go to bed later and rise later. Before puberty, children are predominantly morning people –often very early morning people — much to the chagrin of their parents. In adolescence, there’s a physiologic shift that trends towards later bedtimes, which is why it’s so hard for teens to get up in the morning. Sometime in our twenties, sleep time begins to shift back to an earlier bedtime.
Even without taking the test, you often know your ideal bedtime — that’s the time that leaves you feeling the most refreshed when you get up in the morning. Studies have shown sticking to a sleep schedule that follows your chronotype can improve mood and boost productivity. Unfortunately for many of us, that’s not an option. Life can be difficult for night people who are forced to live out-of-sync with their natural body rhythms. For example, night people may hate it when the alarm clock goes off in the morning for work or to chauffeur the kids to school. Similarly, morning people may feel terrible the day after a late night, or being awakened frequently by a new infant. People who have to work night shifts may suffer most of all. Till Roenneberg, Ph.D., a professor at the University of Munich’s Institute of Medical Psychology, introduced the term “social jet lag” to describe the fatigue experienced by people who are forced to live counter to their innate biological clocks.
Take the case of the teacher who has to get up at 6 am daily. Her desired MSF would be 2 am. So if her natural sleep cycle is 12-8 am, her chronotype is two hours later than she would like it to be. Thus, she would have about two hours of “social jet lag” every day. Chances are, she is relying on frequent doses of caffeine to get through the day!
Even if your body may prefer a later bedtime, in most cases, it’s possible to adjust your sleep/wake time to conform to the demands of your lifestyle. Dr. Canapari notes that sticking to the same sleep and wake times daily is helpful, as is exposure to natural light early in the morning, “Natural light exposure upon waking will keep you on a typical schedule — go outside in the morning light. Light is the strongest entraining factor for the biological clock.” Dr. Canapari adds that in some cases, doctors will prescribe light boxes for people to use upon rising, for those who have an especially difficult time coping with early mornings.
Whether you’re a morning person or a night person, exposure to light at night can disrupt your sleep schedules, especially if it is the blue-white light emitted from a computer screen, smartphone or tablet. Dr. Canapari says that looking at the bright light from a screen, especially one held so close to your face, is a signal to your biological clock to stay up later. “It’s a good idea to put your devices away at least three hours before bedtime, and try not to sleep with your cell phone in the room because it’s too tempting to look at it.“
Cheating yourself of sleep increases the risk of developing both physical and emotional problems, including obesity, diabetes, heart disease and depression. It can also decrease your quality of life, as Dr. Canapari observes, “We all know that we perform better, we’re better workers, we’re better parents, and partners to our loved ones when we’re not irritable, when we’re getting enough high quality sleep at night.”
Dr. Canapari adds that using a sleep tracker to monitor your sleep at home can be the wake-up call you need to get serious. “It’s very easy to go about your life and feel kind of sluggish in the morning, but say, ‘Well, maybe staying up a half an hour later and catching up on Facebook isn’t that big a deal.’ But then you realize that you’re losing 2 ½ hours of sleep — that’s a third of a night’s sleep during the course of a week.”
Tracking your sleep can also help you improve your sleep habits. Dr. Canapari observes, “Let’s say you made a commitment, ‘I want to go to bed earlier than I am.’ Tracking your sleep will keep you honest by providing you with more objective data. If you’re just trying to remember it on your own, you’re just going to remember what you want to remember.“