There are two main types of sleep: REM and non-REM sleep. REM (rapid eye movement) sleep refers to superficial sleep. Studies have shown that during this sleep phase, our eyes move quickly back and forth under closed eyelids. When we are in superficial sleep, we are prone to disturbing sounds that startle us and wake us up. REM is also the sleeping phase in which we dream the most. In this period, we process the information that our brain has collected during the day.

Non-REM (non-rapid eye movement) sleep involves a stage of deep sleep. It is difficult to wake up from this phase. Deep sleep is thought to be the phase in which children’s growth is especially stimulated and memory pathways are formed.

Together, the different sleep phases form a cycle that is repeated several times during the night.

Even in babies and young children, superficial and deep sleep phases alternate. Compared to the adult sleep cycle, there are some differences:

• Your baby’s sleep cycles are relatively short in the first six months of life (approximately 50-60 minutes as opposed to approximately 90 minutes for adults). At the end of such a sleep cycle, babies and toddlers often wake up briefly, whereas adults usually move on to the next cycle without awakening.
• Your baby’s sleep in the first months of life consists of approximately 50% REM sleep periods (compared to about 20% in adults), from which he or she can easily be woken up. During this active sleep period, your child may show sudden movements, make sounds, and even smile (the so-called “angelic smile”). This superficial sleep (as well as frequent awakening at night) is part of your baby’s normal development and has a watchdog function. The child can draw attention to themselves when they are hungry, thirsty, feel uncomfortable or are in danger. (e.g. obstruction of the respiratory tract).
• Increased REM sleep in babies has another important function: it is thought to be important for the development of nerve cells and brain growth.
• In the first 6 months of life, your baby’s sleep starts with superficial REM sleep, whereas older children and adults show non-REM sleep as the first phase. The fact that the baby’s sleep starts with superficial sleep is also the reason why many children at that age have difficulties falling asleep. They often startle before they can fall into a deeper sleep.
• By the age of 5-6 months, sleep changes again: Night sleep begins with a deep sleep phase (similar to adults), followed by superficial and non-REM sleep phases in the second half of the night.