Circadian Rhythms & Chronotypes: How Does Your Body Know When To Sleep?

People, plants, and animals have internal clocks called "circadian rhythms" that help with natural body functions like sleep and keep people on a 24-hour schedule. Each person has their own unique circadian rhythm.

Sleep has its own circadian rhythm that affects when you start to feel sleepy and when you tend to naturally wake up without an alarm. This also impacts when you may feel the most awake or productive during the daytime.

External factors like light exposure, physical activity, timing of meals and other medical conditions can affect your circadian rhythm on a day-to-day basis.

Your Chronotype & How It Impacts Your Sleep

Your circadian rhythm dictates your chronotype, which is your body's natural preferences for sleep and wake.

• "Night owls" are late sleepers that prefer to stay up generally past midnight and wake up late – these people have a "delayed" chronotype.
• "Early birds" or "morning larks" go to sleep early and wake up early – these people have an "advanced" chronotype.

Neither is inherently problematic, except in cases where the natural sleep and wake times don't align with work, school, familial, or other social obligations, which can make for poor quality sleep.

Night owls may struggle to fall asleep early and wake early, while early birds who try to stay up late may still wake up early. Both circumstances may lead to sleep disruption and sleep deprivation.

Can My Chronotype Be Changed?

There is no way to suddenly change your chronotype. There are ways to make small, gradual shifts to your circadian rhythm by changing your habits to encourage your body to sleep later or earlier.

This often involves setting specific times for light exposure, meals, activities, and exercise. Supplementing melatonin at doses of 1mg or less at certain times of day, with the guidance of a sleep medicine specialist, can also help. However, without consistency in these habits, your circadian rhythm will return to its natural schedule. There also may be a part of your chronotype that is due to genetics and may fundamentally never change.

Another aspect to your circadian rhythm and chronotype is age. Oftentimes as you grow older, your circadian rhythms will shift towards sleeping earlier and sleeping fewer total hours in a day.

There are many factors that can impact the quantity and quality of your sleep. If you are having trouble getting to sleep or staying asleep, you should consult your primary care provider.