We all know that getting enough sleep is a must for our health. Here we reveal 5 myths and facts related to the theme of sleep and what science says about each.
Deep sleep, also called slow-wave sleep because of its characteristic brain waves, is crucial for feeling refreshed in the morning. Deep sleep is the most restorative phase of sleep and is associated with vital functions such as growth hormone production, strengthening the immune system, repair and regeneration. However, the assumption that only deep sleep determines how long we should sleep is wrong.
In addition to deep sleep, the other stages of sleep, light sleep and REM sleep also play an important role. Lighter sleep, for example stage N2 sleep, also contributes to memory processing and consolidation and plays a key role in learning and automating movement sequences. For example, athletes should not give up this sleep phase to take full advantage of their training sessions.
REM sleep plays a very important role in our mental health, among other things. During REM sleep, concentrations of noradrenaline, the stress-related and anxiety-inducing chemical, are turned off in the brain, while simultaneously reactivating the amygdala and hippocampus, important brain structures linked to emotion and memory. This allows reprocessing of memories or experiences in a stress-free state. This is probably why REM sleep deprivation has been shown to increase irritability and anxiety and is strongly linked to depression or post-traumatic stress disorder.
Learning:Deep sleep is critical to our rest, but if we get up after completing several deep sleep cycles, we will remember other important sleep stages. Each sleep phase has its own benefits, therefore healthy and beneficial sleep depends on all phases together.
We now know that the narrative and bizarre experiences we often call dreams take place in all stages of sleep, most notably during REM sleep. Therefore, REM sleep is still linked to dream sleep. Other research has focused on the function of dream sleep, highlighting its key role in processing emotions. This can be explained by a particularly favorable neurobiological state of REM sleep in dreams. The increased activity of brain structures related to emotion and memory, especially the amygdala and hippocampus, allow the reactivation of previously acquired affective experiences. Emotions can then be processed in a stress-free and anxiety-free state. To that end, studies have shown that, following a distressing event, sleep attenuates the experience of stressful emotions, decreases amygdala activity, and increases the activity of cognitive control areas such as the prefrontal cortex. Because of this, REM sleep in dreams allows us to gain greater control over the emotions and experiences we have had and to heal emotional wounds.
For emotional processing of events and our well-being, REM sleep in dreams is again a very valuable resource for healing. In addition, while dreaming in REM sleep, memories can be connected in abstract and very new ways. For example, studies showed that during REM sleep, study participants were particularly adept at extracting higher-level rules and sequences from prelearned stimuli or combining them in novel ways. This promotes a brain state that is conducive to solving previously impenetrable problems or generating creative ideas.
Learning:This shows that some myths can be more than just fairy tales and can be taken really seriously. Studies have shown that sleep can really have a big impact on stability and emotional processing.
During the day, the body uses a lot of energy, which produces adenosine and increases its concentration. By attaching to certain receptors, adenosine turns off the areas of the brain that trigger wakefulness while simultaneously activating the areas that induce sleep. Caffeine is chemically similar to adenosine, allowing it to bind and block adenosine receptors without activating areas of the brain that would otherwise be attacked by adenosine. In this way, caffeine reduces the number of free adenosine receptors, inhibits the fatiguing effect of adenosine and exerts a stimulating effect instead. For this reason, caffeine is also called an adenosine antagonist.
Caffeine can affect sleep on several levels, such as falling asleep for extended periods, decreased total sleep time and sleep efficiency, decreased slow wave sleep, or subjectively poorer sleep quality. However, this does not apply to everyone everywhere. The effect and duration of caffeine varies widely from person to person and is dependent on a variety of exogenous and endogenous factors.
Learn:Caffeine aids in alertness and neutralizes sleep-inducing mechanisms. The duration of the coffee's effect depends on several inter-individual factors that have to be taken into account. While for some, caffeine intake in the afternoon can interfere with sleep at night, others can still consume caffeine after dinner without sleeping problems.
Body movements during sleep are not uncommon and occur in all age groups. In general, nocturnal movements decrease with age, although the chances of awakening from them are greater with older age. Studies repeatedly calculate the average values of adult postural changes in the first six hours of sleep. However, these are average values from which significant deviations can occur – without automatically indicating poor sleep or even a sleep disorder.
Studies show that body movements do not occur equally in all sleep phases:Although the body does not move during REM sleep and little in deep sleep, there is more movement immediately before and after REM sleep and in the lighter sleep phases. In addition, it can be shown that body motility is correlated with transitions between sleep stages. Tossing and turning can prolong the transition from light to deep sleep, while movements before REM sleep can help prepare the central nervous system for the onset of REM sleep.
However, if nocturnal postural changes wake us up at night, even for a short period of time, which is called micro-awakening, they can cause sleep fragmentation and thus affect the quality of sleep. An uncomfortable sleeping position or experiencing pain can often cause unrest.
Learn:tossing and turning at night doesn't necessarily mean you're getting very little or poor sleep. How often or how long you move at night can vary greatly from person to person, on average 5 to 16 movements per hour. As long as it doesn't interrupt your sleep, it's not necessarily a cause for concern. However, if pain or discomfort is the cause of the restlessness, action should be taken. This is where choosing the right mattress is crucial, providing optimal firmness to align the spine and support the body without creating uncomfortable pressure points. In this way, unrest can be effectively reduced.
It is a common belief that evening exercise induces physiological arousal and therefore disrupts sleep. Some studies have shown that high-intensity exercise in the evening delays the onset of sleep, for example due to an increased heart rate. In addition, an increase in endorphin levels associated with exercise not only boosts our mood, but also our alertness and brain activity, which can also contribute to difficulty falling asleep. But the investigation goes beyond these facts and cannot simply be stopped at this stage.
Scientific evidence for such negative effects of evening exercise on falling asleep is scarce and has not been replicated in many other studies or meta-analyses. On the contrary, positive effects on sleep have also been shown, such as lower latency to sleep onset or better sleep quality. This can be explained, for example, by a thermogenic effect. During exercise, the body temperature rises and falls again shortly afterwards. This drop in temperature after the end of the workout mimics the natural temperature change that occurs before you fall asleep. In order to fall asleep and maintain a good night's sleep, our body temperature drops by about 0.5-1°C. A sudden drop in temperature caused by physical activity can therefore signal to our body that it is now time to go to bed. However, this only applies if the body temperature changes in a relatively short time and does not remain high for long. Otherwise, the accumulated heat can, in turn, prevent us from falling asleep. This theory is also consistent with the observation that parts of the brain that promote sleep contain heat-sensitive cells. An increase in temperature and its subsequent decrease could therefore activate those parts of the brain that induce sleep and promote sleep.
Another effect of evening exercise is the possibility of a circadian phase shift. Our circadian rhythm, the internal clock that controls our sleep-wake cycle, can (de)synchronize through exercise. A phase reduction can ensure that we fall asleep earlier, a stretch ensures that we stay awake longer. Exercise can help us manipulate and adjust our own internal rhythm. However, inter-individual differences must be taken into account! One study has shown that for late chronotypes, morning and evening training leads to phase shortening. For the previous chronotypes, exercise in the morning led to phase shortening, while physical activity in the evening led to phase lengthening. For the latter group, exercise was therefore an obstacle to falling asleep, while chronotypes benefited from it.
Learning:It is wrong to say that exercising right before bedtime has a negative effect on sleep. Exercising in the evening allows us to align our internal clock with our sleep schedule and fall asleep more easily due to changes in body temperature. Again, this cannot be generalized to all people, so everyone should identify their own preferences and see if exercise promotes or inhibits sleep. But rather than demonizing it in general, it's worth a try because for many of us, this time of day can be a great time to exercise.
