The curtains rip open, the sheets are pulled back. “Get up. You’re wasting the day, Henry!"

We’ve all been there, a teenager on the receiving end of an annoyed parent telling us to get out of bed. Society tells us that hard workers are early risers, while it sees night owls as lazy. But science disagrees.

WHAT IS A CHRONOTYPE, AND WHY DOES IT MATTER?

Your chronotype is your body’s natural sleep-wake preference. Are you a morning type, up at dawn and thriving in the morning? Or are you an evening type, at your best when the rest of the world is asleep? Most people fall somewhere in between.

But your chronotype isn’t a personal choice. It’s written in your DNA. Scientists have found at least nine genes that affect if you're an early or late sleeper.

We all have a 24-hour circadian rhythm, which is our internal clock for sleep and wakefulness. Our chronotype decides where our personal “sweet spot” is on that clock.

For example, a morning type may feel sleepy by 9 pm and wake up refreshed at 5 am. In contrast, an evening type might not get tired until midnight and wake up around 9 am.

And at the extreme ends, the difference can be huge. For example, an early sleeper might go to bed at 7 or 8 pm, while a very late sleeper at 2 am.

WHY DO WE HAVE DIFFERENT CHRONOTYPES?

This diversity isn’t a quirky trait; it likely evolved for survival. Imagine life in a hunter-gatherer tribe. If everyone went to sleep and woke up at the same time, the group would be completely vulnerable for eight hours. If some members like to stay up late, while others wake up early. That would mean there’s a much smaller time when everyone is asleep.

In today’s world, this evolutionary advantage can seem more like a mismatch. Society often favours morning types. Schools start early, workdays run from 9 to 5, and meetings happen before many evening types want to be awake.

HOW UNDERSTANDING YOUR CHRONOTYPE CAN IMPROVE YOUR SLEEP

Knowing your chronotype can help you optimise your sleep and daily routine. If you’re always going against your natural rhythm, you may feel tired all the time. You might even think you have insomnia, but the real problem is timing.

An evening person who tries to sleep at 9 pm might have trouble falling asleep. Their body just isn't ready for it. Likewise, a morning type trying to stay up past midnight might feel utterly drained. Adjusting your schedule to match your chronotype, even a bit, can boost both the amount and quality of your sleep.

CHRONOTYPE ACROSS THE LIFESPAN

Interestingly, though your chronotype is genetic, it isn’t set in stone. It also evolves as you age.

• CHILDREN are naturally early to bed and early to rise.
• TEENAGERS experience an exaggerated shift forward. Staying up late and sleeping in are a biological reality for teens. But this often clashes with early school starts and adult norms.
• ADULTS usually find a steady routine in their 20s and 30s. Their real chronotype starts to show.
• SENIORS often go back to a child-like schedule. Capturing the seniors' market is why restaurants introduced "early-bird specials.”

THE HIDDEN DANGERS

Fighting your chronotype can also harm your health. If your job makes you work late or change shifts, you are likely hurting your immune system, productivity, and mood.

Working night shifts can disrupt your natural sleep cycle by 12 hours. Research shows that shift work can raise the risk of heart disease, diabetes, and cancer. The World Health Organisation has classified night shift work as a probable carcinogen.

What we can learn from that is that by ignoring your chronotype, you’re putting your health on the line. It also makes you really appreciate the sacrifices that shift workers have to make.

BIAS AND WHAT WE CAN DO ABOUT IT

Alas, society isn’t exactly kind to evening types. Morning people seem to have the upper hand. Early work meetings, strict school schedules, and social norms all favour them. But by understanding chronotypes, we can start to counter these biases.

For instance, if your team includes a few evening types, skip the 9 am brainstorming session. If you have a teenager at home, let them sleep in when possible. It helps them recover from the sleep debt they build up during the week. Small adjustments can make a difference to people.

TAKE THE TEST

Curious about your chronotype? A simple questionnaire, like this one, can give you a good idea.

Don’t worry too much about lions, bears, dolphins, or other such chronotypes you might see on the internet. Your sleep-wake cycle comes from genetics and light exposure, not your personality.

Working with your chronotype improves sleep quality, boosts productivity, and lowers health risks. So if you're an evening type, embrace it and try shifting meetings or deep work to later in the day. For some of us, going to bed late isn’t so bad after all.