What is your chronotype? Morning lark, night owl, or somewhere in between

Some people wake at six feeling bright and ready. Others are only getting going by ten at night. Most of us sit somewhere in between. That natural timing has a name: your chronotype.

What a chronotype is

Your chronotype is the timing your body clock prefers. It shapes when you naturally feel sleepy, when you wake without an alarm, and when you feel most alert during the day.

It is not a habit or a lifestyle choice. Every cell in your body keeps time, and those clocks are kept in step by a master clock in the brain, the suprachiasmatic nucleus. How early or late that clock runs differs from person to person, partly because of the genes we inherit.

People often talk about "larks" and "owls". In reality chronotype is a spread rather than two boxes. A small group are strongly early, a small group strongly late, and most people fall in the middle.

How to work out yours

Researchers usually use questionnaires rather than blood tests. The two best known are the Morningness-Eveningness Questionnaire, published in 1976, and the Munich ChronoType Questionnaire, which looks at when you sleep on work days compared with free days.

You can get a rough answer with one simple question. On a day with no alarm and nothing planned, what time do you naturally fall asleep and wake up? Take the midpoint between the two.

• A midpoint around 2am or earlier suggests an earlier chronotype.
• Around 3am to 4am is the middle of the range.
• Around 5am or later suggests a later chronotype.

It is only a guide, and it works best if you have not been short of sleep that week.

Why it changes through life

Chronotype is not fixed for life. Young children tend to be early risers. Through the teenage years the body clock shifts later, which is why many teenagers genuinely struggle to fall asleep early or to get up for school. The latest timing usually peaks around the age of twenty, then drifts earlier again through adulthood. Many older people find themselves waking earlier than they used to.

Where light comes in

Your genes set the starting point, but light decides where your clock actually sits each day. The body clock runs on a cycle that is not exactly 24 hours, so it needs a daily nudge to stay in time with the world. Light is the strongest nudge it gets.

Light in the morning tends to pull the clock earlier. Bright light late in the evening tends to push it later. That is why the same person can drift later on holiday or through a dark winter, and earlier after a week of camping outdoors.

Modern indoor life makes this harder. Most of us spend close to nine tenths of the day indoors, where light is far dimmer than daylight, then sit under bright screens and lamps late into the evening. For anyone with a naturally late chronotype, that combination can push the clock later still. We explain the wider picture in our guide to circadian lighting.

Social jet lag

When your body clock and your timetable disagree, the gap has a name: social jet lag. It is the difference between when your body wants to sleep and when work or school makes you sleep. Late chronotypes tend to feel it most during the week, then "catch up" at weekends, which shifts the clock again and makes Monday harder.

The clocks changing twice a year is a small version of the same problem that everyone shares.

Working with your chronotype

You cannot change your genes, but you can help your clock sit where you need it:

• Get daylight early in the day, ideally outdoors. Even a cloudy morning is far brighter than a typical room.
• Keep evening light softer and warmer as bedtime approaches, and put bright screens away a little earlier.
• Keep sleep and wake times reasonably steady, including at weekends.
• Where you can, put the work that needs most focus at the time of day you feel sharpest.

What this means for lighting

Most buildings are lit the same way for everyone, all day. Yet the people inside them run on different clocks. At Sensio BioLabs we are researching how the light people actually receive indoors, through the whole day, could be shaped around the person rather than the building. It is early work, and we will share what we learn.

This article is for general information and is not medical advice. If you have ongoing problems with sleep, speak to your GP.