Baby Sleep Patterns and Consequences for Life

In order to further understand baby sleep patterns better, scientists have been examining the day-night routine of animals whose DNA is very similar to that of human beings for over 70 years. A new paper written by scientists from Harvard Medical School, The University of Iowa and Michigan State University brings this research together and draws some interesting conclusions.

The sleep-wake cycle is a key element in the development of human beings and is closely related to possible behavioural problems that occur later in life, such as neurodegeneration. Some forms of obesity, sleep disorders and even hormonal imbalances have their roots in the improper formation and balance of the sleep-wake cycle. This sleep wake system located in the brain goes through an enormous development in the first three weeks of a baby’s life, but it can also be influenced by external factors, such as daylight. Scientists believe that understanding how our biological rhythms develop, as well as how and what regulates them, will provide us with more information on the early development of babies’ brains.

Adults sleep around eight hours a day, of which two hours are rapid eye movement (REM) sleep. But babies sleep approximately 16 hours a day, of which eight hours are REM sleep. So, not only are they sleeping longer, but a much higher percent of their sleep is REM sleep. While we still don’t know exactly why this is, most scientists believe it is because the additional sleep (particularly REM sleep) provides the neural stimulation that babies need to form and bring to maturity neural connections in their brain and develop a proper nervous system.

One of the unusual things about sleep in early infancy is that babies transition rapidly between brief, or fragmented, bouts of sleep and wake. They are much more wakeful on and off than adults are. This pattern has also been observed in lots of other mammals, including rats.

The recent paper focused on the sleep-wake sequence of the Norway rat and showed significant development of the way in which the brainstem works together in establishing the circadian/daily rhythms (any biological process that occurs in 24 hours). They showed that the sleep-wake rhythm is created during the very early stages of life and suggested that this is similar in the case of human beings.

The sleep-wake process is regulated by the brainstem and a small part of the hypothalamus. The researchers pointed out that malfunctioning regulation of this process is likely to be playing a role in sudden infant death syndrome (SIDS), which has a peak occurrence in infants between 2 to 4 months – right when the sleep-wake process is supposed to be consolidated and a rhythm established. It shows how important the establishment of sleep patterns are: without proper control of arousal, the brain cannot “tell” the body to awake from sleep, leading to illnesses and even death.

Other elements documented in the paper are the two “switches” that pertain to the sleep-wake cycle. One switch makes the transition between the state of being conscious and that of sleeping, while the second is responsible for the triggering of rapid eye movement (REM) sleep, or active sleep. REM sleep deprivation triggers imbalances throughout a mammal (including humans), both mentally and physiologically, which is why this type of sleep is is so important.

So, what can we take from all this?

Babies and toddlers up to three years of age will spend more time sleeping than being awake – this is normal and healthy. However, this is also the time when their sleep-wake rhythm is consolidated, especially in the early days. This sleep-wake rhythm can have consequences for life so it’s important to maximise a child’s ability to get to sleep and stay asleep when they need to be.

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