Can you change your sleep schedule?

Here we see an early bird and

a night owl in their natural habitats. The early bird rises with the sun,

springing out of bed abuzz with energy. As the day goes on, they slowly get

more and more exhausted until finally crashing around sunset. Meanwhile, the night owl rises

long after the sun, stumbling groggily from their bed. After about 30 minutes—

or a cup of coffee— they begin to come to life. But they don’t really hit their stride

until later in the day, at which point they comfortably

coast past sunset, only heading to bed in the early hours

of the morning. For many, this is a familiar story,

and one that’s easy to cast yourself in. But how many people are truly

night owls or early birds? And are our natural sleep schedules

predetermined at birth, or can we change them? The truth is there’s a lot of space

between these extremes, and most people fall somewhere

in the middle. These behaviors are determined

by our circadian system— which is anchored by a pair

of nerve cell clusters located in the anterior hypothalamus. These nerve cells respond to light

exposure coming in through your eyes to track the day-night cycle that dictates

your body’s internal clock, or circadian rhythm. That steady rhythm helps determine

the body’s flow of hormones, with the broader circadian system

acting like a conductor that keeps your organs functioning

in time with one another. And a major part of that performance

is managing the body’s transitions between being awake and being asleep. Now, your circadian system can't just

decide its bedtime and knock you out. However, by tracking how much

light you typically get and when in your waking hours

you usually get it, the system can make predictions about

when you’re likely to need sleep and prepare your body accordingly. For example, if you consistently

go to sleep around 10 pm, your circadian system will start producing

sleep-inducing melatonin around two hours before then

to tell your body it’s time for bed. So if this rhythm is molded

by our sleep habits, can we change it just by sticking

to a strict schedule? To a degree. Everyone’s bodies are unique, so even two people with the same sleep

schedule might have different experiences based on their circadian system’s

hormonal quirks. For example, where early birds generally

flood with cortisol just before waking up, night owls often have their cortisol peak

roughly 30 minutes after getting up. Hormonal differences like these determine

how you experience your circadian rhythm. And while these factors

can shift with age, you’re unlikely to grow out of your body’s

preferred sleep schedule. That said, you can cultivate habits

to help or hinder your circadian rhythm. Keeping consistent sleeping hours helps

your body accurately predict when to send out hormones, making it easier to stick

to your schedule. Conversely, research in sleep deprived

college students has found their unpredictable

sleeping habits weaken their entire circadian system. Compromised circadian rhythms

are less effective at coordinating organ functioning

and can incur health risks like metabolic disorders

and vulnerable immune systems. But perhaps just as important

as sleep hygiene is light hygiene. Getting sufficient contrast between

bright daylight and dimmer nighttime light is essential for synchronizing

your circadian rhythm, and nothing establishes this contrast

better than sunlight. Even on overcast days, sunlight is much

brighter than standard indoor lighting. So if you're typically

awake during the day, try getting outside as soon as possible

to teach your body when to be active and alert. It’s difficult to maintain

a sleep schedule that pushes against your

body’s preferences. And even if you succeed for months, it only takes one bad night to send

your circadian system back to baseline. But whether you’re an early bird,

night owl, or somewhere in between, it’s important to remember

that as long as you’re consistent, there’s no wrong time

to wake up or go to sleep. What matters most is getting enough rest

for the day ahead.