May 28, 2025, 9:05 am | Read time: 9 minutes
We go to sleep when we’re tired and wake up when we’re rested. Most people know all too well that it’s not that simple. Struggling to fall asleep at night, lying awake unintentionally, and dragging ourselves out of bed exhausted in the morning—this is often the reality. During my current training to become a sleep coach, I came across an intriguing theory: The clock is the enemy of our sleep. In this article, I explore this idea. What exactly does it mean, and is it true?
I don’t really need to think long about it: Is the clock the enemy of my sleep? Absolutely! Because when my alarm goes off in the morning and I’m not ready to get up, it feels exactly like that. But I want to know more. What does sleep research say about it: Is the clock the cause of our various sleep problems, even sleep disorders? An overview.
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Overview
How does our body know when it’s time to sleep and wake up?
By nature, every person has a biorhythm or an internal (biological) clock. It controls countless processes in the body, such as cell division or blood pressure, including the sleep-wake cycle. This is genetically determined and lasts a lifetime. The interplay of the hormones serotonin, cortisol, and melatonin ensures that we go through this cycle daily: sleep, wake up, stay awake, get tired, and finally sleep again.1 The sleep-wake cycle follows the circadian rhythm, meaning a 24-hour cycle. This is essentially the same for all of us. Depending on the sleep type, it is only slightly shifted overall—toward early waking and sleeping or late waking and sleeping. Of course, the clock plays a role in this classification. After all, who or what determines what is early or late? Correct: The modern daily rhythm, which is oriented around clock times. More on that later.
Different Sleep Types
First, a brief digression on sleep types. They often come up in discussions about sleep, such as in studies.2 These studies suggest that late sleepers and risers, also known as “owls,” are more likely to have health risks than early risers and sleepers, also known as “larks.”3 Again, the reference to the clock. The negative effects described in research often seem to be related to the fact that people who would naturally wake up later because they sleep later and only then get enough sleep, must start their day early due to the clock (representing externally imposed schedules and time stress), thus shortening their sleep.
But back to sleep types or chronotypes. They describe the individual sleep-wake rhythms of people. Everyone has such a rhythm, with different phases of wakefulness and tiredness over 24 hours. But exactly when someone is more tired or alert varies greatly. Surely, we all know people who are wide awake at seven in the morning without an alarm and can perform at their best, but fall exhausted into bed at 8 p.m. On the other hand, there are those who seem to drag themselves through the day, would prefer to sleep until 11 a.m., and only really wake up in the late evening.
There are many gradations on the scale from early to late types. And even within one’s own chronotype, there can be variations over the course of life. But basically, according to sleep research, we remain primarily an early, neutral/normal, or late type throughout our lives.4
Why the Clock Is Not Good for Our Natural Sleep
As already hinted, the clock often contradicts our internal clock. This is especially felt by people like me, who find it difficult to go to bed early and would naturally not start their days at seven but have to: the owls, in other words. My clock is definitely more of an enemy than a friend in the morning.
In sleep research, various factors are known that can temporarily or permanently disrupt sleep. The clock is described as the main disruptive factor of our biorhythm, or rather the way it is used in the modern world. Originally, it was simply a timekeeper; today, it determines our entire daily routine. We have to catch the train or bus at a certain time in the morning to be at work or school at a specific time. Whether it’s doctor’s appointments, shopping, or errands at offices, everything follows the rhythms dictated by clocks. Even our leisure time with sports, parties, or other social events is scheduled according to the clock.
A late type may suffer from having to be highly focused and creative or make decisions at work by eight in the morning but enjoys warm nights with friends. Larks, on the other hand, would prefer to start working at six in the morning but have to muster the energy for some social gatherings at 8 p.m., as they would rather gradually go to bed at that time.
Social Jetlag
Admittedly, this is sometimes exhausting and annoying, but that’s life, you might think? You’re right. But what many people perceive as normal and hardly question can lead to genuine health problems. Because when the alarm abruptly ends our sleep in the morning, even though our internal clock hasn’t prepared us to wake up yet, it shortens our sleep time.
If this happens occasionally, like on trips in the form of the so-called jetlag, it’s not a big deal. We settle back into our rhythm. In the case of the alarm that rings for work and, for example, throws late types out of bed against their internal clock system, this is considered more serious. The “social jetlag,” as it’s called in this context, leads to sleep deprivation that becomes chronic. Such chronic sleep deficit can develop into sleep disorders (insomnia) and have drastic consequences for well-being and health. Known negative impacts include effects on the cardiovascular system, metabolism, and even mental health (depression, anxiety disorders).5
As the example described suggests, the “social jetlag” weighs differently from chronotype to chronotype. Late types, who would biologically start their day later, tend to suffer more from it than early types—not only in the short term in the form of tiredness but also regarding the mentioned long-term health consequences.
What Studies Have Found
Countless studies have tried to decipher the connections between chronotypes, sleep behavior, and the use of the clock or the alarm function of clocks in detail. Researchers have often been able to show that it has effects when people wake up not on their own but because of an alarm. While the body’s processes have not yet reached the waking point, the alarm forces it to interrupt the natural waking process prematurely. Normally, cortisol would signal the body that it’s time to wake up and ensure that we feel rested and alert. But since the process is interrupted and the cortisol hasn’t yet been able to “do its job,” we continue to feel tired after waking up.
More than that. There is scientific evidence that the shortened sleep duration can also affect sleep phases, specifically REM sleep. In a study from 2023, chronotypic sleep loss led to a destabilization of REM sleep. This is of great importance for brain regeneration. It is considered essential for memory, emotional balance, and cognitive performance. Late sleep types were particularly affected by sleep loss and its effects.6
Another study from 2013 showed that not only late but also early types can suffer under modern schedules that work against their internal clock. A study of shift workers suggested that larks particularly struggle with late and night shifts. When they had to be active late into the evening or even into the night against their biorhythm, they experienced a pronounced social jetlag. Late types were affected—not surprisingly—when they had to do early shifts. Night shifts, however, were less of a problem for them.7
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Let’s summarize: The clock and the strict modern schedules associated with it, which determine daily life, often clash with our natural sleep needs. But what can be done?
Ideally, we could completely align our daily lives with our chronotype. Realistically, this is not possible for most people. But there are smaller ways. We can try to adjust the levers available to us and orient our lives as much as possible to our sleep needs.
Some people might actually be able to change their job or even career in the long term if it stands in the way of their personal sleep-wake rhythm and thus their health. Others may not have this option.
Adjust Day and Evening Activities
Early risers may not get their dream work hours from six to 1 p.m., but they could complete their exercise routine right in the morning and not meet the night owl among their friends at the gym at 8 p.m. Adjustments will be more challenging for late chronotypes. Although they know the alarm will ring at seven in the morning, they are still wide awake on the couch at midnight. However, they should also consider rethinking their evening activities. Don’t keep yourself awake with video games, streaming, or scrolling on your phone. Late intense training sets your hormones more on stress and activation. Instead, try calming rituals: read a book, do light yoga and/or breathing exercises, and try to relax earlier.
Turn Off the Alarm on Weekends
One last tip: Disconnect from your clock as much as possible. By this, I mean what is often referred to as “living into the day.” Many only know this on trips. But maybe you can also manage to turn off the alarm on weekends and only get up when you wake up naturally. And if there are no appointments, why not avoid looking at the clock? Just let yourself drift through the day and go to bed when you’re tired.
Incidentally, it seems that you can catch up on sleep to some extent on weekends. Those who suffer from a sleep deficit during the week apparently benefit from sleeping longer on weekends. At least that’s the result of recent studies.8,9,10 Well then: Good night!