When you visit a family with a baby, you are faced with a high probability that the baby is sleeping. About 70% to be exact. That’s because babies can naturally sleep 11-19 hours a day.
The American Sleep Association’s recommended sleep times for babies aged 0-3 months are 14-17 hours a day. Children 4-11 months old also need to sleep from 12-15 hours. Children over 1 year old need 11-14 hours of sleep. Under 5 years old, children still need 10-13 hours of sleep.
Scientists have long asked a question: Why does the younger the child need more sleep? Now, a new study in the Science Advances journal helped them answer that question.
For toddlers, their lives are filled with new experiences. That is why babies need sleep in order to load these new experiences into the brain, researchers say. The learning and memory process is enhanced by REM sleep, which spans about half of the child’s sleep time.
During the other half of sleep, a child’s brain performs an equally important task. It needs to clear out the trash, transport accumulated substances to avoid brain poisoning. This is basically the same as when you run “Disk Cleanup“in the C drive of the computer.
For these reasons, scientists claim that early sleep is an essential condition for the development of normal brain functions in children. And it follows an amazing mathematical model.
The importance of sleep is compressed over a very short period of time in childhood and brain development. “I was shocked to see this change happen so drastically in a very short period of time“, Says Van Savage, an ecologist and evolutionary biologist at the University of California, Los Angeles.
“And this transition happens at a time when we are very young. It’s similar to the process of freezing water.”
In their latest research, Savage and his team argue that sleep was developed to serve several major functions for humans and animals in general. “It is almost certain that many of the physiological functions needed are dependent on long, time-consuming sleep“, he said.
The most important and major part of sleep is called REM, or fast rolling sleep. In adults, REM tends to start about an hour and a half after napping. This sleep phase helps us consolidate the experiences we have during the day, deepening them into each person’s memory bank.
Infants spend about half of their sleep in a REM state. By the age of 10, that number drops to just a quarter. After the age of 50, humans only have 15% of their sleep time to form memory in their REM.
This logic leads to the theory that infants need a long amount of REM sleep to strengthen their developing brains. Children need to remember all the information they need in life to survive and grow.
But despite the very long REM sleep, the question is, what do babies do for about half of their sleep?
Scientists say it is time for the newborn to do brain cleaning and repair. If you get enough long REM sleep, but the amount of sleep is too short, your child’s brain will accumulate waste products, increasing the risk of nerve damage in the future as the baby grows up.
To prove this, Savage and his team used data from dozens of sleep studies to find correlations between age, body size and sleep length. This is a comprehensive model based on both neuroscience, biology and mathematics, which helps us to better understand the human sleep pattern from young to old.
In babies, the brain is the part that grows faster than the rest of the body, Savage said. Therefore, it requires the body to focus all its resources here, making the most of the time it takes to build connections.
Brain development and need for sleep is a proportional relationship. And that’s not just true of humans. Savage put in his simulation both rabbits and two rats’ sleep data.
The analysis showed that rabbits and newborn rats also slept as much as children under 2 and a half years old. Then as their age and body size increase, their sleep time will shorten.
Prolonged sleep in infancy could be an important trait that is preserved in all mammals, the scientists hypothesize. “The brain is doing something really wonderful and very different in this period“Said Savage.
If you can’t get enough sleep, what could be the consequences? Do animals have brain disability problems? Will speech and motor learning of sleep-deprived infants be affected?
Those are questions that need to be answered in the future. Now, Savage research has reinforced one more reason that allows us to let our babies sleep. Do nothing to wake them up, if you visit a new family with a baby.