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Podcast Episode 21: Sleep as the key to a clear mind with Dr. Declercq
Sleep affects everything: your energy, concentration, stress levels, and even your weight. Yet, many struggle with insomnia, overthinking, and a restless mind. In this episode of the Amandine De Paepe Podcast, in collaboration with WOW Health Talks and Generation WOW, Amandine and Barbara De Beir talk with Dr. Inge Declercq, neurologist, sleep expert, and author of Breinrust.
They discuss why sleep is so crucial, which habits disrupt your sleep, and how to improve sleep quality without medication. Dr. Declercq explains how screen use, caffeine, social jet lag, and an overactive mind affect your rest and shares practical strategies to sleep better and wake up refreshed.
About Dr. Inge Declercq
Dr. Inge Declercq is a neurologist, sleep expert, and founder of Sleepwell & Stressless. In addition to her work at UZ Antwerp, where she focuses on sleep-wake consultations, she gives workshops and lectures on sleep and stress management. With her scientific background, she translates complex knowledge into practical tips that anyone can apply.
Sleep routine and the importance of a healthy biorhythm
Dr. Declercq emphasizes that sleep is a 24-hour process. How you live during the day determines how well you sleep at night. She follows a fixed sleep routine, in which stretching plays an important role. Every evening, no matter how late it is, she takes the time to stretch. Her morning routine also contributes to good sleep: upon waking, she drinks a large glass of water, stretches in bed, and tries to get some daylight immediately.
According to her, respecting the biorhythm is crucial for a good night's rest. A slow start to the day, such as having a relaxed breakfast with a newspaper, helps the body wake up naturally.
The different sleep disorders
Sleep disorders fall into six main categories:
1. Insomnia – People with insomnia do sleep but are too awake during the night. This significantly impacts daily functioning and affects 1 in 4 Belgians.
2. Breathing-related disorders, such as sleep apnea – This often goes unnoticed but can have serious health consequences.
3. Excessive daytime sleepiness – Some people fall asleep anywhere and consider it normal, but it can be a sign of an underlying sleep disorder.
4. Movement disorders, such as restless legs syndrome – This mainly affects women and can cause major difficulties falling asleep. A low ferritin level in the blood may play a role, and avoiding caffeine often helps reduce symptoms.
5. Parasomnias – This includes nightmares, sleepwalking, and night terrors.
6. Sleep-wake rhythm disorders – Shift workers are particularly affected by this, as their natural clock is out of sync with their working hours.
How lifestyle and nutrition affect your sleep
Amandine points out that many people underestimate how much nutrition, stress, and medication impact their sleep. For example, eating fatty foods and certain medications, such as statins, can cause muscle cramps, which disrupt sleep.
Dr. Declercq takes a holistic approach to sleep. Her expertise in chronobiology and stress-coping techniques allows her to view sleep from a broader perspective. She emphasizes that sleep is not only influenced by what happens in the bedroom but that everything you do during the day, from nutrition to stress management, plays a role in sleep quality.
The difference between men and women in terms of sleep
Barbara refers back to restless legs, which primarily affect women, and asks if there are other differences based on gender or age. Sleep problems in women during perimenopause and menopause are well known. Restless legs, however, are less linked to age—they can occur in young girls with iron deficiency due to heavy menstruation, during pregnancy, and later in life.
Men, on the other hand, are more prone to snoring and sleep apnea. This is partly because fat accumulates more easily between the esophagus and the windpipe, obstructing breathing during sleep.
Hormonal influence also plays a significant role. Women in menopause often struggle with sleep problems due to a decline in estrogen and progesterone. Men and women not only experience sleep differently but also have distinct physiological causes for their sleep issues.
Overthinking and the science behind a restless mind
Many people experience intense and chaotic thoughts at night. Neuroscientific research shows that this is caused by an imbalance between two brain networks:
- The default mode network, which helps with creative thinking and allows thoughts to flow freely.
- The executive network, responsible for rational thinking, decision-making, and control.
At night, this balance often doesn’t function properly, making thoughts feel uncontrollable and minor worries seem overwhelming.
An effective way to break the cycle of overthinking is to literally get up, breathe calmly in the dark, visualize something, or write down your thoughts. This helps the rational brain regain control and reduces overthinking.
It's also crucial not to check the clock when waking up. This creates stress, activating the brain’s alert mode and making it even harder to fall back asleep.
The importance of disconnecting during the day
Many people feel they don’t have a sleep disorder yet still experience chronic fatigue and low energy. This is often due to a lack of mental rest moments throughout the day.
Dr. Declercq likes to compare it to a wind-up toy. When you stay "switched on" all day without taking breaks, the toy winds up completely. By the evening, it’s at its limit, and you become overstimulated. The result is poorer sleep quality, with frequent nighttime awakenings and less restorative deep sleep.
To improve sleep quality, it's crucial to take regular short breaks during the day. Simple actions can help, such as:
- Going outside for some fresh air.
- Doing a few stretching exercises.
- Practicing mindful breathing or briefly closing your eyes.
- …
Many people believe they only need to relax in the evening, but Dr. Declercq emphasizes that micro-breaks throughout the day are just as important. These should be breaks without a phone, moments where you can completely disconnect from work.
Those who accumulate too much stress during the day unconsciously carry it to bed, increasing the likelihood of overthinking and restless nights.
Research has shown that these micro-breaks have a real impact on sleep quality. People who take them regularly—ideally every 45 minutes—tend to feel much less stressed in the evening and require less time to unwind after work.
Chronotype and the biological clock
Everyone has a chronotype, a biologically determined rhythm that dictates when you naturally feel tired and when you're most alert. According to Dr. Declercq, about 30% of this is genetically determined. Other factors, such as hormones, light exposure, seasons, and age, also play a role.
The better you align your life with your natural sleep-wake rhythm, the healthier you will be. People who respect their biorhythm generally experience better sleep quality and have more energy throughout the day.
Social jet lag: a disrupted biological clock
Many people experience social jet lag, a term coined by chronobiologist Till Roenneberg. This occurs when you are forced to wake up at an unnatural time during the workweek (for example, at 6 AM for work) while your biological clock would prefer 8 AM. As a result, you sleep in on weekends, shifting your sleep-wake pattern.
Our society is largely structured around early chronotypes, even though this doesn't match the natural rhythm of many people. This pattern can have negative health effects, such as:
- Reduced sleep quality
- Increased fatigue and concentration problems
- Higher risk of chronic conditions
To minimize these effects, it's best to maintain a consistent sleep schedule with as little variation as possible between weekdays and weekends.
What happens when your sleep rhythm shifts?
Some people feel extremely tied to their biological clock. For instance, they can only sleep well if they go to bed between 10 and 11 PM. When they deviate from this schedule, such as staying up late for a party, they experience sleep issues.
Dr. Declercq explains that part of this may be conditioning—the belief that you can only sleep within a strict timeframe, causing your brain to experience stress when that schedule is disrupted.
However, there is an important nuance: constantly going against your chronotype leads to sleep deprivation and stress. This is why it's essential to align your sleep as much as possible with your natural rhythm. After a disruption (like a late night out), it’s crucial to prioritize relaxation, such as stretching before bed, to help restore balance.
In short, respecting your biorhythm is one of the most powerful ways to improve sleep quality and overall health.
The impact of daylight saving time on our biological clock
The transition from standard time to daylight saving time negatively impacts our biological clock, mainly because we lose an hour of sleep. According to Dr. Declercq, this is harmful to our biorhythm since we are suddenly forced to wake up an hour earlier while our internal clock doesn’t adjust as quickly.
Moreover, daylight saving time causes a two-hour shift from the natural solar time, further disrupting our rhythm. This misalignment with the sun has negative effects on sleep and overall well-being.
Teenagers are especially affected. Their hormonal development naturally makes them evening types, making it harder for them to wake up early. Research shows that 16-year-olds would function better if school started at 9 AM, leading to:
- Fewer depressive symptoms
- Better academic performance
- Improved mental well-being
Despite strong scientific evidence, little consideration is given to this issue. This makes maintaining a stable sleep rhythm and getting enough morning light even more important.
Why do you sometimes sleep worse than expected?
Barbara asks a familiar question: "Why do you sometimes expect to sleep well, but the opposite happens?" You feel utterly exhausted, anticipate a deep sleep, yet wake up in the morning still feeling drained.
According to Dr. Declercq, this is due to stress and adrenaline. You may feel physically tired but still be mentally overstimulated. She again highlights the lack of disconnecting throughout the day, which keeps stress levels too high.
She also explains that being tired and being sleepy are biologically two different things. You can feel exhausted in the evening, but if you've accumulated too much stress, your body may not yet be ready to truly fall asleep. You’re tired, but not sleepy.
Another phenomenon can occur during the day: you might expect to feel extremely tired, yet suddenly find yourself in a flow state, feeling focused and productive. This happens partly due to caffeine, which blocks the sleep-promoting chemical adenosine and dopamine, which temporarily increases motivation and alertness.
However, this pattern can create a vicious cycle:
- Your sleep is not truly restorative.
- Your body compensates during the day with stress hormones and external stimulation.
- By the evening, you’re too overstimulated to fall asleep properly.
Dr. Declercq emphasizes that the key to breaking this cycle is to take regular breaks during the day. By doing so, you go to bed feeling less stressed, and your sleep won’t be negatively impacted by accumulated mental tension.
The quality of a power nap: fact or myth?
Amandine shares a story about her father, an entrepreneur who has always worked a lot and claims he only needs four hours of sleep per night. He compensates by taking two ten-minute naps a day, saying they make him feel completely refreshed. She asks Dr. Declercq whether this is a good approach.
Dr. Declercq responds with skepticism. Sleeping only four hours per night leads to chronic sleep deprivation, which is harmful in the long run. Only three percent of the population has a genetic mutation that allows them to function properly on six hours of sleep. For most people, this is simply not enough.
Amandine’s father’s power naps likely do not make up for his sleep deficit. Instead, they temporarily suppress daytime sleepiness, helping him feel more alert. However, the fact that he needs these naps suggests that his four hours of sleep per night are insufficient.
How to take an effective power nap
Power naps can be beneficial, but only when done correctly:
- A power nap should only be used to overcome sleepiness, not to compensate for chronic sleep deprivation.
- The ideal duration is no longer than 20 minutes. Sleeping longer can disrupt your sleep-wake cycle.
- Power naps should be taken at least 8 hours before your nighttime sleep, or they may interfere with your sleep cycle.
If you feel tired but not sleepy, a nap is not the best solution. Instead, it’s better to go outside, get some daylight, and engage in physical movement to restore your energy levels.
Can you catch up on lost sleep?
Barbara wonders if it’s possible to make up for lost sleep. Some say that going to bed earlier for a few nights can compensate for missed rest. But is that really true?
Dr. Declercq confirms that you must make up for sleep debt, as chronic sleep deprivation has long-term health consequences. Research shows that regular sleep deprivation increases the risk of neurodegenerative diseases like Alzheimer’s, cardiovascular diseases, autoimmune disorders, and even cancer.
However, it’s not as simple as just sleeping earlier for a few nights. The way you recover sleep is crucial:
- The best way to recover from sleep debt is by gradually extending your sleep duration over multiple nights.
- This doesn’t necessarily mean going to bed earlier but rather sleeping in longer in alignment with your biorhythm.
- Early chronotypes (morning people) can go to bed earlier, while late chronotypes (night owls) benefit more from sleeping in, as their biological clock is naturally set that way.
The larger your sleep debt, the longer it takes to fully recover. If you’ve accumulated years of sleep deprivation, one weekend of sleeping in won’t be enough to restore balance. That’s why Dr. Declercq strongly emphasizes the importance of a stable sleep routine, so you never build up chronic sleep debt in the first place.
Physical vs. mental fatigue
There is a significant difference between physical and mental fatigue, and this distinction can greatly impact sleep quality.
Physical fatigue
Physical fatigue results from bodily exertion, such as intense exercise or physically demanding tasks. Barbara gives the example of feeling completely exhausted after a long bike ride, as if she has "hit a wall." This type of fatigue primarily originates in the body and is felt in the muscles.
Mental fatigue
Mental fatigue, also known as cognitive or central fatigue, has a different cause. It arises from prolonged mental effort, such as working on a screen for hours, excessive thinking, or being under high stress. This type of exhaustion is less physically noticeable but can feel mentally overwhelming and even lead to a deep sense of exhaustion.
Impact on sleep
According to Dr. Declercq, mental fatigue doesn't always improve sleep quality. In fact, if it's accompanied by stress or overstimulation, it can make falling asleep more difficult. Stress affects neurotransmitters, making it harder for the brain to transition into sleep mode.
People who are physically tired generally fall asleep easily. However, those who are mentally exhausted but not physically active may struggle with sleep quality.
This highlights the importance of:
- Physical activity during the day, so the body is genuinely tired by the evening.
- Stress reduction and mental relaxation throughout the day and before bedtime to prevent overstimulation of the brain.
Without proper relaxation, mental overload can cause micro-fragmentations in sleep, disrupting deep sleep and making it less restorative—often without the person even realizing it.
Insomnia in parents
Dr. Declercq explains that insomnia can take on a life of its own, especially for parents of young children. Many parents go through a phase where they wake up frequently at night because their baby or toddler needs them.
But what happens when the children finally sleep well? Some parents continue to struggle with sleep problems, even though the original cause (their child's restless nights) has disappeared.
This happens because insomnia can become a vicious cycle:
- The habit of waking up at night lingers, even when there's no external reason for it.
- The body and brain become conditioned to stay alert, fearing that sleep will be interrupted again.
- The stress of sleep deprivation remains, making it harder to fall asleep or stay asleep.
Cognitive behavioral therapy
For chronic insomnia, the most effective approach is Cognitive Behavioral Therapy for Insomnia (CBT-I). This is a scientifically proven method that helps break negative sleep habits and thought patterns.
According to Dr. Declercq, CBT-I is more effective than sleep medication, as it addresses the root cause of insomnia rather than just suppressing symptoms. It helps people regain confidence in their ability to sleep naturally, preventing insomnia from becoming a long-term issue, even after an extended period of disturbed nights.
Debunking sleep myths
Barbara asks Dr. Declercq if there are any persistent sleep myths she would like to debunk. Many tips and recommendations about sleep circulate, but not all of them are correct.
1. You can't catch up on lost sleep
As previously mentioned, this is incorrect. Sleep debt must be recovered, as chronic sleep deprivation has long-term health consequences. How you recover depends on the severity of the deficit:
- The greater the sleep debt, the longer it takes to fully recover.
- You can’t make up for years of sleep deprivation in just one weekend.
- The best way to compensate for lost sleep is to gradually extend your sleep duration, preferably by sleeping in within your natural biorhythm.
2. Sleep is a waste of time
According to Dr. Declercq, this is a dangerous misconception. In reality, poor sleep is what truly wastes time—not sleep itself. Sleep is essential for:
- Physical and mental health
- Memory and concentration
- Recovery and overall well-being
3. You must be in bed before 10:00 PM for a good night's sleep
This is not true for everyone. The myth that "the hours before midnight count double" only applies to early chronotypes, and even then, not entirely.
Everyone has a personal chronotype, and what truly matters is aligning your sleep schedule with your natural biorhythm rather than following an arbitrary bedtime rule.
4. Power naps can compensate for sleep debt
Power naps can help with temporary daytime sleepiness, but they do not make up for chronic sleep deprivation. While short naps (max. 20 minutes) can be refreshing, longer naps or napping too late in the day can disrupt nighttime sleep.
Dr. Declercq emphasizes that many persistent sleep myths still exist and that relying on scientific research is essential to optimizing sleep properly.
The impact of smartphones on sleep
Barbara asks Dr. Declercq whether smartphones and other screens are truly such a big enemy of good sleep. The answer is a resounding "yes," and this is due to two key reasons.
1. Light stimulation disrupts the biological clock
Screens emit blue light, which affects the production of melatonin, the hormone that makes you sleepy. Even with a blue light filter, this effect remains, especially in people over 30.
When you spend a long time on your smartphone, tablet, or laptop in the evening, your body receives the signal that it is not yet time to sleep. As a result:
- Your sleep is delayed
- Your biorhythm is disrupted, especially for late chronotypes
- It can take longer to fall asleep
2. Mental and dopamine stimulation
Besides the effect of light, smartphone use also has a mental and neurological impact. Scrolling through social media, checking emails, or reading the news activates the brain’s reward system and stimulates dopamine production. This keeps you mentally alert and engaged rather than relaxed and ready to sleep.
Is there a difference between watching TV and using a smartphone?
Yes, according to Dr. Declercq, watching TV is less harmful than using a smartphone, but only under certain conditions:
- The distance from the screen matters: the farther away, the less impact on melatonin production.
- It's better not to watch TV in the dark, so the light intensity is less strong.
- Avoid scrolling on your smartphone while watching TV, as this increases mental stimulation.
The biggest issue remains that many people use their smartphones in bed, which negatively affects sleep both due to the light and the mental stimulation.
The best solution: digital detox before bedtime
Dr. Declercq recommends avoiding screens for at least one to two hours before bedtime. This helps to:
- Normalize melatonin production
- Calm the brain
- Sleep better and deeper
Using screens right before bed is not only bad because of the light but also because it keeps you mentally active at a time when you should be relaxing.
Are there quick fixes for better sleep?
Amandine asks Dr. Declercq what the quickest or first step is that people can take to improve their sleep quality. Do quick fixes exist? Is it better to reduce screen time, lower stress, or focus on nutrition?
Dr. Declercq is clear: there are no real quick fixes for sleep. Sleep is a complex process influenced by many factors, and what works differs for everyone. There is no one-size-fits-all solution.
However, there is a common thread: everyone is neurobiologically programmed to sleep at night. It is a natural process, but you need to give your brain the right signals for it to function properly.
What is the first step?
What you should address first depends on your lifestyle. In her workshops, Dr. Declercq sees that 80% of people indicate that screen use is their biggest issue. This is why reducing screen time in the hour before bedtime is an important first step for many.
Other common factors that disrupt sleep:
- Consuming caffeine too late in the day
- Stress and mental overload without enough relaxation
- Irregular sleep schedules that disrupt the biorhythm
It is essential to critically examine your own habits and make the first feasible change. Even small steps can make a significant difference.
A personal term: disconnection balance
Dr. Declercq introduced the concept of "disconnection balance," a term she has even trademarked. This idea revolves around letting go of the strict separation between work and private life and instead seeking a natural balance.
The issue: work and private life as opposites
Many people experience a constant duality between work and private life. It is often said, "I need to find a balance between my work life and my personal life." However, by setting these two against each other, you automatically create a stressful contrast. This makes it feel as though work and private life are competing, adding extra tension.
What is disconnection balance?
Disconnection balance means not viewing work and private life as two opposing worlds but rather as a continuum. Since COVID, it has become increasingly clear that work and private life are intertwined. This does not have to be a problem, if managed in a healthy way.
An example of this is working from home. Instead of feeling guilty for taking a moment for personal matters during the day, you can see it as a short mental break. This helps you return to work more productively.
Practical application: how to create balance
- Taking short breaks during work to do something for yourself—such as going for a walk or completing a small household task—can help maintain energy levels.
- Being mindful of the transition between work and private life: when you come home, truly take time for your family or hobbies without being distracted by work emails.
- Letting go of guilt: taking a short break during the day makes you more productive. Shifting back to work in the evening does not have to be an issue if done consciously.
Why is this important?
Amandine notes that a colleague often seems to feel guilty about taking short breaks during work. For example, she enjoys going for a run around 3 PM.
According to Dr. Declercq, this kind of flexibility is the key to a healthy disconnection balance. She advocates for employers and employees to embrace this new way of thinking so that people no longer feel guilty for managing their energy and focus in a healthy way.
By consciously alternating between effort and relaxation, without rigid boundaries, we can better support our mental and physical health in the modern work culture.
A calm mind for better sleep
At the end of the conversation, Dr. Declercq shares several practical tips for reducing nighttime worrying and calming the mind. Many people find themselves stuck in stressful thoughts in the evening, thinking about unfinished tasks or past mistakes. This can severely disrupt sleep.
The worry corner
One of the techniques Dr. Declercq recommends is using a "worry corner." This means deliberately scheduling a moment before bedtime to organize your thoughts:
- Write down worries in a notebook or journal to get them out of your mind.
- Do this outside the bedroom—your brain should not associate your bed with worrying.
- Reassure yourself by deciding that you will think about these matters only the next day.
Going to bed: a process of relaxation
It's also important to signal to your brain that it's time to sleep. This can be done through:
- A relaxing bedtime routine (such as stretching or calmly brushing your teeth).
- Breathing exercises to release stress.
- Visualization techniques, where you imagine your thoughts drifting by like clouds.
- Reading a few pages of a book: this is calming as long as it's not a suspenseful thriller.
Belief in your own ability to sleep
According to Dr. Declercq, having confidence in your ability to sleep is essential. Many people convince themselves that they are simply "bad sleepers," but sleep is a natural process. By developing the right habits, almost everyone can improve their sleep quality.
Sleep is not just a nighttime matter. What you do during the day directly affects your rest at night. By regularly disconnecting during the day, actively letting go of worries, and following a peaceful bedtime routine, you give yourself the best chance for a restorative, deep sleep.
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