Six hours and six minutes. That’s how long Danira Boukhriss slept on average during the week her sleep was tracked. She has a baby who has been keeping her awake for nine months and says she even goes to bed with anxiety. A relatable case of sleep deprivation, and the starting point for the “Sleep” episode of Over mijn lijf on VRT MAX. While Danira gets tips, Kobe Ilsen flips his biorhythm and works three consecutive night shifts, guided by neurologist and sleep expert Dr. Inge Declercq. It’s funny, sometimes painfully relatable, and surprisingly educational. But is everything they say correct? I’ve listed the most striking moments and fact-checked them.
Sleep deprivation: it’s about more than just hours
Dr. Inge Declercq mentions seven to nine hours as the average requirement for adults. This aligns with the consensus advice from American sleep societies: at least seven hours on a regular basis (Watson et al., 2015). Those guidelines also state that individual needs vary.
I found her division into three pillars the most useful part of the episode: how much you sleep, how well you sleep, and how regular your sleep-wake rhythm is. That explains why a long night alone isn’t always enough.
Why going to bed earlier doesn’t always help
Danira tried to make up for her deficit by going to sleep earlier. It didn’t work: she is a later type and lay awake at a time when her body wasn’t ready for sleep yet. Declercq’s tip was surprisingly simple: only lie down when sleepiness hits. And yes, Danira fell asleep faster after that.
That’s not just a TV trick. It resembles a component of CBT-I, the treatment for insomnia: reconnecting the bed with sleeping instead of lying awake.
Kobe is the other extreme. Saliva tests showed that his melatonin peaked before seven in the evening. According to the figures in the program, 13 percent of people are morning types, 60 percent are intermediate types, and 27 percent are evening types. Other sources mention different distributions; what is clear is that morning and evening people really do differ.
How much light do you need? Danira’s lux meter
My favorite experiment of the episode: Danira walks around for a day with a lux meter. Different times, different places inside and outside the house, showing clearly visible differences. The difference between indoors and outdoors is huge, and now that it’s getting dark early again in November (when we published this), that’s extra interesting.
Dr. Declercq mentions the morning as the ideal time to let in plenty of light in the episode. The international consensus on indoor light uses a different measure, melanopic EDI, which better aligns with how light affects the biological clock: at least 250 during the day, at most 10 in the three hours before bedtime, and at most 1 in the bedroom at night (Brown et al., 2022). A standard lux meter doesn’t measure that. So, see those lux numbers as a helpful guide, not a hard standard. The message holds up: more light during the day, less in the evening. You can read more about that under light therapy.
Two weeks without screens: what does that prove?
A family with two teenagers gave up all screens after 8 PM for two weeks. The result was great: more conversations, more energy, and one of them saw thirteen minutes more deep sleep on his watch. Declercq calls the impact of screens obvious.
A nice case study, however, it involves just one family without a control group, and sleep trackers are less reliable for sleep stages than for distinguishing between being asleep and awake (Chinoy et al., 2021). In the lab, four hours of reading on a luminous screen did suppress melatonin and shifted the clock (Chang et al., 2015). But a recent review shows that the link between screens and sleep is more complex: the content, the arousal, and the time the screen steals from your sleep also count (Bauducco et al., 2024). Perhaps the gain from such an evening isn’t just the missing blue light, but also the game and the conversation that took its place.
Night shifts: not everyone is cut out for them
Kobe follows a security guard, a port crew, and a bus driver, among others. Some have been working nights for twenty years and wouldn’t have it any other way; others find it particularly tough. According to Inge Declercq, a lot depends on your type, and early types adapt the worst. Research supports this: among shift workers, early types slept shorter and worse during night shifts (Juda et al., 2013). After three nights, Kobe scored significantly worse on the Vias tests.
That makes the drive home the most serious moment of the episode. According to Dr. Declercq, if you’re sleepy, it’s better to stop and take a quick nap: ten minutes is said to be good for about an hour of driving. That’s pretty close to driving simulator studies, where a nap of less than fifteen minutes temporarily reduced sleepiness (Reyner and Horne, 1997). So it remains a delay, not a solution.
Laser on your back: the mattress part
Then the part I was especially looking forward to. Ergonomic advisor Pascal Mannekens visits people at night and uses a laser and a tight suit to see how their back is positioned. His conclusions are relatable: a pillow that is too thick can disrupt the alignment, a firmer mattress often suits a higher weight, and the entire sleep system matters: mattress, bed base, and pillow. These are also the questions behind mattress firmness and weight. According to him, lying on your stomach all night is the most difficult, because your neck remains twisted.
I would nuance one statement: that a mattress is full of waste products after ten years. Ten years is a common rule of thumb, and the statement is plausible, but I couldn’t find any hygiene research supporting that specific timeframe. How a mattress has been used and whether it still provides support seems at least as important to me.
Three facts I quickly double-checked
- Don’t look at the clock. According to Dr. Declercq, that brings you back into the waking world. Experimental research with people suffering from insomnia points in the same direction: clock-watchers worried more and estimated their time to fall asleep as longer (Tang et al., 2007).
- Delay coffee by half an hour. A review article on caffeine finds little support for such waiting rules (Antonio et al., 2024). It certainly can’t hurt, but there is no hard evidence.
- Sleeping pills. According to the program, one in five Belgians has taken them at some point. In the 2018 Belgian health survey, 12 percent of adults used such medications (BENZONET). Both figures measure different things, but it is very clear that it involves far too many people.
Sleep is not wasted time
What sticks? I can’t boil it down to a single tip, but rather the image of two tired people who need very different things. For Danira, whose child got sick, small adjustments were enough to notice a difference. For Kobe, the lesson was mainly how quickly your performance declines, even when you think you’re doing fine. Or as Declercq concludes: “Never say that sleeping is a waste of time.” If I had to boil it down, it wouldn’t be a tip but a question: which of those three pillars deserves your attention first? I’m really curious about the answer!
Frequently Asked Questions
Where can I watch Over mijn lijf about sleep?
The episode “Sleep” (season 1, episode 4) is available on VRT MAX (Belgium), according to the page until October 7, 2027. It lasts 44 minutes.
How many hours of sleep is enough to avoid sleep deprivation?
Consensus advice for adults regularly mentions at least seven hours, and seven to nine hours is often maintained. However, needs vary per person. How rested you feel during the day also says a lot.
How many lux do you need per day?
In the episode, 10,000 lux per day is mentioned, with 1,000 lux in the morning. That is not an official standard. The international consensus uses melanopic EDI: at least 250 during the day, at most 10 in the evening.
Can you make up for sleep deprivation?
According to Declercq, you’re largely through it after a few good nights of seven or eight hours, if the deficit was short-lived. It’s different for long-term sleep problems, and in those cases, a GP can help.
Sources
- Antonio, J. et al. (2024). Common questions and misconceptions about caffeine supplementation. Journal of the International Society of Sports Nutrition. doi.org/10.1080/15502783.2024.2323919
- Bauducco, S. et al. (2024). A bidirectional model of sleep and technology use. Sleep Medicine Reviews. doi.org/10.1016/j.smrv.2024.101933
- BENZONET (Belspo). Summary with figures from the 2018 Health Survey. belspo.be
- Brown, T.M. et al. (2022). Recommendations for daytime, evening, and nighttime indoor light exposure. PLoS Biology. doi.org/10.1371/journal.pbio.3001571
- Chang, A.M. et al. (2015). Evening use of light-emitting eReaders negatively affects sleep. PNAS. doi.org/10.1073/pnas.1418490112
- Chinoy, E.D. et al. (2021). Performance of seven consumer sleep-tracking devices compared with polysomnography. Sleep. doi.org/10.1093/sleep/zsaa291
- Juda, M., Vetter, C. and Roenneberg, T. (2013). Chronotype modulates sleep duration, sleep quality, and social jet lag in shift-workers. Journal of Biological Rhythms. doi.org/10.1177/0748730412475042
- Reyner, L.A. and Horne, J.A. (1997). Suppression of sleepiness in drivers. Psychophysiology. doi.org/10.1111/j.1469-8986.1997.tb02148.x
- Tang, N.K.Y., Schmidt, D.A. and Harvey, A.G. (2007). Sleeping with the enemy: clock monitoring in the maintenance of insomnia. Journal of Behavior Therapy and Experimental Psychiatry. doi.org/10.1016/j.jbtep.2005.07.004
- VRT (2025). Over mijn lijf, season 1, episode 4: Sleep. VRT MAX
- Watson, N.F. et al. (2015). Recommended amount of sleep for a healthy adult. Sleep. doi.org/10.5665/sleep.4716