REM sleep and deep sleep: definition, effect and consequences.

REM sleep, also known as REM sleep (Rapid Eye Movement), is the phase of sleep phase phase of sleep, generally lasting between 15 and 20 minutes. During this stage,brain activity accelerates considerably, almost as if the sleeper were awake. Rapid eye movements are frequent, and muscle tone is virtually non-existent, leading to muscle atony or paralysis. The EEG (electroencephalogram) shows accelerated brain waves, while heart rate and respiratory rate become irregular.

Unlike deep slow wave sleep, which is primarily restorative for the body, REM sleep plays a crucial role in mental recovery and memory. It's also during this phase that most dreams occur, making it a vital part of the sleep cycle. This stage of REM sleep is all the more important as thebiological clock programs several episodes over the course of a night's sleep, each separated by phases of light and deep sleep.

And deep sleep?

 Deep sleep is the phase before REM sleep and is an integral part of slow-wave sleep slow wave sleep. It generally sets in 30 to 45 minutes after falling asleep. In contrast to REM sleep, this phase is characterized by increased muscle relaxation, a drop in pulse and blood pressure, and a reduction in respiratory rate and body temperature. Vital signs become stable, eye movements cease, and brain waves, measured by electroencephalogram (EEG), show slow delta waves, a sign of very deep sleep.

It is during this stage of sleep that phenomena such as sleepwalking or night terrors can occur. Deep sleep is also essential for the secretion ofgrowth hormone, which is particularly crucial for the development of infants and children. This stage of sleep is physically restorative, allowing the body to recover from accumulated fatigue and the cells to regenerate. The central nervous system goes into standby mode, reducing metabolic activity throughout the body.

However, a lack of deep sleep over a prolonged period can lead to significant psychological disorders, including mood disorders, aggressive behavior, and mental disorientation. It is therefore an essential part of sleep architecture, and occurs in different cycles throughout the night, alternating with phases of light sleep and REM sleep.

REM sleep in babies

During the first nine months of life, a child's sleep is very different from that of adults. The circadian rhythm, the biological mechanism that regulates the waking and sleeping cycle over a 24-hour period, is not yet fully developed in newborns. Babies can sleep between 16 and 20 hours a day, divided into several sleep cycles lasting between 50 and 60 minutes.

Around two months of age, the baby's sleep pattern begins to modulate, and around three months, what was previously restless sleep evolves into more distinct REM sleep. By the age of six months, this phase accounts for around 35% of total sleep time, and by nine months it often disappears from daytime naps.

As sleep is a crucial stage in a baby's development, it's important to respect his sleep needs, to be alert to any nocturnal awakenings or sleep disorders, and to understand the different stages so as to better meet his needs.

Sleep and alcohol

Alcohol can seriously disrupt the various stages of sleep, particularly REM sleep, which it tends to reduce. If alcohol consumption occurs just before bedtime, sleepers can expect a more restless and poorer quality sleep . In addition, sleep disorders such as insomnia, sleep apnea syndromesand increased snoring are frequently observed. Brain electrical activity and breathing can also become irregular during sleep.

Alcohol also affects sleep patterns, making it harder to fall asleep and wake up. This disturbance often manifests itself in nocturnal awakenings or fragmented sleep, affecting total sleep time and quality. It can also induce excessive daytime sleepiness, impairing alertness and activities the following day.

To prevent these harmful effects and sleep better, we strongly recommend moderating alcohol consumption, especially in the hours before bedtime. This can help maintain restful sleep and a healthier sleep cycle.

Sleep and antidepressants

People taking antidepressants may also experience difficulties with REM sleep, which can range from drowsiness to insomnia. This is why patients need to be monitored by their doctor to help them regain a better quality of sleep.

Sleep and weight

Sleep deprivation can have an impact on obesity as they are closely linked. If sleep is disrupted, ghrelin will be produced in excess, prompting the body to eat more, even if it really needs it. Today, scientists distinguish between ghrelin, which activates appetite, and leptin, which is responsible for satiety.

But lack of sleep has a direct impact on the synthesis of these hormones: ghrelin is produced in abundance, while leptin is produced less and will have an impact on weight gain.

Sleep and snoring

Snoring is a noisy sound made when air passes through the airways. There are many causes of snoring, including excess weight, alcohol and tobacco consumption, medication (sleeping pills), nasal congestion, an angled nasal septum, sleeping position, etc..

Snoring can occur during different phases of sleep. Deep sleep may be more intense, unlike REM sleep, which may cease at this point. Depending on the sleep phase, snoring may change, but it's best to determine the cause first: Sleep apnea which is fairly widespread.

Sleep is an important stage for human beings. From birth to adulthood, a good quality of life is essential for good sleep and good health.