Book Extract | How to Sleep Like a Caveman by Dr Merijn van de Laar

Book Extract

Excerpted with permission from the publisher How to Sleep Like a Caveman: Ancient Wisdom for a Better Night’s Rest,‎ Dr Merijn van de Laar, published by William Collins/Harper Collins India.

*******Do numbers tell the tale?

In modern times, people feel an increasing urge to get to grips with their own health via new technologies. Smartphones have functions that indicate how many steps you’ve taken in a day, blood pressure meters are sold in pharmacies, and smartwatches can measure your activity levels, as well as your body temperature, blood oxygen levels and heart rate. Some even claim that they can track stress levels by measuring electrical currents on the surface of the skin. Users can opt-in to end-of-day reports of dropping and spiking stress levels to help identify patterns that might explain why they are feeling stressed out. There is the idea that everything related to health should be expressible in figures and that this gives a good representation of how you are doing physically.
Many smartwatches also measure sleep quality, which translates into a ‘sleep score’, and fancy graphs show what percentage of REM and NREM sleep has been achieved over the last couple of nights. The questions arise: first, are these measurements accurate, and second, do they help create a better night’s rest? Does it make sense to express sleep in numbers?

Polysomnography is the gold standard for measuring objective sleep. An important characteristic of this sleep examination is, next to other factors of interest, that it measures brain activity. Devices currently available to consumers cannot measure this aspect. Most wearables use accelerometers, heat-flux sensors and optical blood flow sensors to indicate sleep or wake.

In addition, they try to give an impression of which phase of sleep you are in. Several studies have compared consumer sleep technologies with polysomnography and concluded that most devices and apps are not helpful in the estimation of sleep phases, but can give a reflection of total sleep and wake time in healthy individuals who do not have insomnia. A recent literature review concluded that there are new promising techniques that make wearable devices more accurate. Examples of these techniques are photoplethysmography (measuring changes in blood volume), artificial intelligence (which helps to make better computations), and new measurements such as heart rate variability.

However, interpretating results is often difficult, as manufacturers regularly use vague and undefined terms, such as ‘sleep score’. This can lead consumers to place value on a score that may not be well founded. As I mentioned earlier, as a therapist I frequently encountered people who only felt worse if they saw a low sleep score on their smartphone, while it was unclear what this score meant and on what it was based. A recent review study concluded that newer apps are quite reliable in measuring sleep stages in normal sleepers. But how you interpret that data is key here. For example, 10 per cent deep sleep may be enough for one person to function properly, while someone else needs 20 per cent. There is also a lot of personal variation in this.

So how much stock should you put into these sleep scores? I think that in most cases it is important to just go with your gut feeling. If you are a normal sleeper and want to keep track of your rhythm and the variations you have in the amount of sleep, a consumer application may be something for you. For people with insomnia, tracking sleep using devices and apps without professional treatment is not advised, because they are not reliable enough to measure sleep duration or sleep stages. In patients with insomnia, a tracker generally overestimates total sleep time. In studies, one device performed better at estimating total sleep time but underestimated deep sleep and overestimated light sleep. Wearable devices are most suited to healthy individuals to support general wellness and lifestyle modification. In patients with sleep problems, it is a concern that consumer sleep technologies might lead to a preoccupation with checking sleep – a condition known as ‘orthosomnia’ – and an increase of insomnia complaints.

When people with insomnia are treated by a sleep professional, who can carefully interpret the results of a sleep tracker and can make sure the patient isn’t constantly checking, a wearable device might aid cognitive behavioural treatment. Research shows that the advantage is not so much that the use of an app leads to better treatment results, but that it can remove the burden of keeping a sleep log.

So, to sum up, sleep trackers are becoming more accurate in the estimation of sleep. In normal sleepers, they are good at measuring sleep and noting waking – new applications can even reliably estimate sleep phases. However, the interpretation of results, such as sleep scores, is not clear or reliable. Even if your sleep phases are reliably measured, it remains difficult to estimate what this means for you because there is a lot of individual variation in what is a healthy score. In people who do not have insomnia, the advice is not to use trackers to monitor sleep without professional guidance as results are less accurate in this group when it comes to sleep and wake states. In addition, unguided use can lead to an aggravation of insomnia symptoms caused by over-frequent checking. If people with insomnia are in treatment, a tracker may be able to support the monitoring of sleep, for example during cognitive behavioural therapy.

Social media influencers

People get their information about sleep from different channels and social media is a growing source of sleep information. However, the possible evidence for this information is often not checked and people can be misguided. There are many examples on social media of sleep advice which is not supported by research. An example recently circulating on TikTok and Instagram was the idea that taping your mouth shut at night should lead to better sleep quality and less snoring.

Data is available on mouth-taping and sleep, though this is mainly focused on a small sample of obstructive sleep apnoea patients. Again, researchers did not examine regular sleepers but a very specific group with a very specific sleep disorder. In this study, mouth-taping led to a reduction of snoring and sleep apnoea complaints. This might in turn lead to an improvement of sleep quality in this group. The catch is that some influencers interpreted these results to mean that every sleeper would benefit from mouth-taping, while this can be dangerous without professional direction as it can lead to hampered breathing (among other things). Nevertheless, the effect was that many celebrities and athletes started promoting mouth-taping.

Is the role of social media here a bad thing? I think it is. In general, it is very important to give clear information on what type of intervention is suitable and for which group of people. Those who are experiencing insomnia might get the idea that mouth-taping is the solution for them, but this can be misleading and potentially dangerous. The same goes for influencers advocating certain types of vitamin pills and supplements to promote better sleep. As we saw in Chapter 5, the sleep-enhancing effects of most supplements are not evidence-based. It is essential that consumers make well-considered decisions when buying a product, and know if claims for its efficacy are based on scientific findings or not.

Another example of social media influencers going wild is the ‘5 a.m. club’. Many influencers promote people getting up very early, saying it will help their circadian rhythms and create more energy. This does not take into account that there are many people with eveningness who, if they feel the pressure to join in with this trend, might deprive themselves of (even more) sleep by getting out of bed even earlier. Again, a clear scientific basis for such statements is missing, and it might be harmful for some people to follow this advice.

The more positive side of the work of many social media influencers is that they often have large global audiences and very persuasive ways of imparting ideas. Scientists could learn from this. I think a big problem in sleep science is that many very good scientists are not able to communicate information and reach large audiences in attractive ways. Both influencers and scientists have a responsibility to spread accurate sleep knowledge and could benefit from each other’s strengths: one group by backing up their statements with scientific research and the other by conveying information in ways that are more accessible and impactful. In the future, I hope they will combine forces more often. For now, always consult your doctor or sleep expert first and don’t rely on the opinion of that celebrity influencer!

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Dr Merijn van de Laar, How to Sleep Like a Caveman: Ancient Wisdom for a Better Night’s Rest,‎ William Collins/Harper Collins India, 2025. Pb. Pp.304

Sleep has hardly changed since Paleolithic humans snoozed soundly in their caves. While sabre-toothed tigers were their biggest night-time worry, today it’s stress and social media that keep us awake, but the solutions are the same, and sleep therapist Dr Merijn van de Laar offers understanding and advice to have you sleeping better within weeks.
How to get a better night’s sleep in 3 weeks:
• Don’t believe everything you read or hear about sleep
• Let go of the 8-hour rule
• Use the simple sleep diary in the back of this book to record your sleep pattern over 3 weeks
• Discover your personal sleep needs
• Examine your attitude towards lying awake at night
• Shorter total bed times might be better
• Focus on the reason for lying awake rather than on the reason for not sleeping
• Reduce stress
• Keep regular bedtimes
• Follow the rules of nature
• Respect your personal circadian rhythm
• Don’t tempt the night-time ghosts
Human sleep as we know it today evolved hundreds of thousands of years ago, to suit a hunter–gatherer lifestyle. It’s not always compatible with our modern lives, but remains an essential function, vital for our health, well-being and daytime functioning. In this groundbreaking new book, Dr Merijn van de Laar investigates the origins of sleep based on archaeological findings and anthropological studies in contemporary hunter-gatherers, looking at the major discrepancies between our primordial bodily needs and our current sleep-inhibiting behaviour.

Cave dwellers lived in balance with the forces of nature. They had adapted perfectly to environmental influences such as light, temperature and seasonal variations. The way they ate and moved during the day must have had a positive effect on sleep quality. We need to look to their example, and adjust our eating, exercise, light, temperature and, last but not least: our expectations towards sleep. By taking on board the ancient wisdom of our ancestors, we will improve the quality of our sleep, the way our bodies were designed to do it.

Dr Merijn van de Laar obtained his doctorate on the subject of personality and sleep and the treatment of insomnia. He worked for years as a sleep scientist and sleep therapist and he is deputy head of the family medicine programme at Maastricht University. He is also a frequent guest on TV and radio.