Skip to main content
Home » Sleep Sensitivity » Biological Differences Between Night Owls and Early Birds
Sleep Sensitivity

Biological Differences Between Night Owls and Early Birds

Is your biological clock effecting your energy during the day through your sleep at night? The answer is yes. Most of us have some degree of preference for late nights or early mornings. Where an individual falls on this spectrum determines his or her chronotype — a genetic disposition toward the timing of daily periods of activity and rest. These genetics are expressed directly by your biological clock and controls your energy and sleep cycle.

Identifying chronotypes

In my recent book “The Power of When,” I help people identify what their chronotype is and how to use this information to their advantage for daily activity. Some of us are early risers while others of us are distinctly night people. The rest fall somewhere in between.

Research has found evidence of structural physical differences in the brains of different chronotypes. Yes, you read that correctly, they have different brains.

Compared to the others, night owls showed “reduced integrity of white matter” in several areas of the brain. White matter is fatty tissue in the brain that helps communication among nerve cells. Reduced integrity of the brain’s white matter has been linked to depression and to disruptions of normal cognitive function.

The cause of this difference in quality of white matter among night people is not clear. This study is the first to offer physical evidence of neurological differences among people with different sleep tendencies. But other research has also shown that the inclinations toward staying up late or rising early are deeply rooted in biological and genetic differences.

The alarm clock gene

Scientists have also discovered an alarm clock gene that activates the body’s biological clock in the morning from its period of overnight rest. In 2012, scientists identified another gene variant that exerts a strong influence over the biological clock and with the inclination to stay up late or rise early. This genetic variation can shift the timing of an individual’s 24-hour sleep-wake cycle by as much as 60 minutes.

Research has also revealed differences in brain metabolic function among night people compared to early risers and middle-of-the-road sleepers. These metabolic differences were discovered in regions of the brain involved in mood, and may be one reason why night people are at higher risk for depression related to insomnia.

If our preferences for sleep and wake times are strongly influenced by genetics and circadian rhythm, what are we to do when our social world does not match up with our genetics?

Better sleep choices

Limiting nighttime exposure to artificial light and increasing exposure to daytime sunlight can shift sleep-wake cycles earlier. Healthy sleep habits —  sticking to regular sleep and wake times and making sure your bedroom is dark and electronic-gadget free — can help reinforce your sleep schedule, even if it doesn’t align perfectly with your natural tendencies.

I hope we’ll see society begin to recognize the power of our chronotypical circadian sleep patterns, and the need for flexibility to enable people to construct schedules that align better with their dispositions toward sleep.

Next article