We spoke with him about why sleep matters, the simple worry list he often recommends, what he thinks of sleep trackers and mouth taping, and what he does after a bad night.

What happens when we sleep, and why does it matter so much?

Sleep is complex, but in simple terms it is the body’s main period of recovery and maintenance. While we sleep, the brain processes and consolidates memories, and sleep supports our metabolism, immune system, muscles and mental wellbeing.

It also supports almost every other healthy habit. When you sleep badly night after night, you often have less energy and motivation to eat well, move and keep learning. That can quickly become a downward spiral.

One bad night is usually not a problem, so there is no need to panic. But if poor sleep becomes a pattern, it deserves attention. Everything else often becomes easier once sleep improves.

Is there such a thing as catching up on sleep at the weekend?

To some extent, yes, but it is not a complete reset. Sleeping longer after a few short nights can help you feel and function better, but it does not fully undo the effects of repeated sleep restriction.

The best approach is to get enough sleep on most nights and keep your wake-up time reasonably consistent, both during the week and at weekends. That does not mean you can never sleep in. It simply means avoiding a schedule that shifts by several hours every weekend.

How much of a good night is decided before you even get into bed?

Quite a lot. Ask yourself: when did I last eat? When did I stop working? How much time am I spending on screens? These things can have a real impact on that night.

Your sleep is influenced by both ends of the day. A consistent wake-up time and morning daylight help anchor your rhythm. The way you wind down in the final hours also matters.

The 3-2-1 rule can be a useful rule of thumb: avoid a heavy meal in the final three hours, finish work and heavy workouts around two hours before bed, and reduce stimulating screen use during the final hour. 

How much does the room itself matter, and how do you find what works for you?

It matters, especially if the room is too warm, bright or noisy. A cool, dark and well-ventilated room works well for many people. Around nineteen degrees can be a useful starting point, but there is no single perfect temperature for everyone. 

Bedding and sleepwear mainly matter because they influence comfort and temperature. Some people sleep better under a weighted blanket, while others prefer something very light. The goal is to feel comfortable and avoid overheating.

The most important thing is to find what works for you, and then be consistent with it. If you sleep better in a certain fabric, sleep in that fabric. Don't follow a protocol or a set temperature just because you read it online. Test it: does this improve my sleep? If yes, keep it. If not, drop it.

What does your own evening routine look like?

My phone is plugged in and out of reach early in the evening, and I read. I usually have two books on the go, one non-fiction and one fiction. I start with non-fiction and spend the final half hour reading fiction in bed. It helps my mind move away from work. When I start feeling sleepy, I put the e-reader away and usually fall asleep like a log.

I also go to bed and wake up at the same time, as consistently as I can. No heavy meals late, no working in the evening, and I read something a bit boring, because scrolling is far too much excitement.

And when the mind just will not switch off at night?

It is one of the questions we hear most often. People have a busy day, get into bed and suddenly their mind switches on. They start replaying the day and running through tomorrow’s list.

One simple technique is a worry list. Before bed, write down tomorrow’s tasks, your worries and anything you are afraid of forgetting. For some people, putting it on paper makes it easier for the mind to let go.

If you are lying awake and becoming frustrated, get out of bed and do something quiet in dim light. Return when you feel sleepy again. The idea is to help your brain associate the bed with sleep, rather than with hours of worrying. This is related to stimulus-control techniques used in cognitive behavioural therapy for insomnia.

If this keeps happening for weeks or months, it is worth asking for help. Chronic insomnia deserves more than a list of sleep tips.

What is the most overrated sleep advice right now?

There is one hype I keep seeing: sleeping with mouth tape to encourage nasal breathing. The idea may sound plausible, but the evidence is limited and it is not harmless for everyone. If someone has nasal obstruction or unrecognised sleep apnoea, taping the mouth can make breathing more difficult.

If you regularly breathe through your mouth, snore loudly or have pauses in your breathing, it is better to investigate the cause than to tape over the symptom. Start with the fundamentals before looking at hacks.

And sleep trackers, scores and all the optimising?

Like many gadgets, sleep trackers help in some situations and do the opposite in others. If the data makes you curious about broader patterns, it can be useful. If it makes you anxious or fixated on getting a perfect score, it can make sleep harder.

Consumer wearables estimate sleep. They do not provide a diagnosis and they cannot prove that one small change caused a better or worse night. Look at trends over time and combine the data with how you actually feel. Do not let one number decide how your whole morning will go. I recommend everyone to determine for yourself how well you slept and how well-rested you feel, before looking at your sleep score.

We all have bad nights. How do you recover from one?

Get some daylight and move, but keep it sensible. A walk or gentle-to-moderate exercise can help you feel more alert. It does not erase the sleep loss, and a personal-record workout is probably not the best idea if you feel poorly recovered.

Try to return to your usual rhythm rather than compensating too aggressively. And do not drive if you are struggling to stay awake.

A final word?

Do not let one bad night convince you that the whole day is ruined. Be a little kinder to yourself, return to the basics and give the next night the best chance you can.

And really, if everyone slept a little better, the world would be a better place.

ABOUT DR FREDERIK DIERICK

Dr Frederik Dierick is a longevity doctor and co-founder of Healthiest, a Belgian preventive health and longevity programme that combines in-depth health testing with personal medical guidance throughout the year.

Learn more at www.healthiest.be.