In yet another piece of research into the burgeoning world of sleep, Science News is reporting results of a new study out of the University of California, Los Angeles. Researchers bolster the theme of “repair” that begins shortly after early childhood. 
Specifically, before the age of 2 or 3 years, the human brain grows rapidly while building and strengthening synapses. After 2 or 3 years, however, sleep’s primary purpose switches from brain building to brain maintenance and repair, a role that continues through a lifetime.
“All animals naturally experience a certain amount of neurological damage during waking hours, and the resulting debris, including damaged genes and proteins within neurons, can build up and cause brain disease,” write Science News staff. “Sleep helps repair this damage and clear the debris—essentially decluttering the brain and taking out the trash that can lead to serious illness.”
“Nearly all of this brain repair occurs during sleep,” said study senior author Professor Van Savage, a researcher in the Departments of Computational Medicine and Ecology and Evolutionary Biology at the University of California, Los Angeles, and Santa Fe Institute in the article. “I was shocked how huge a change this is over a short period of time, and that this switch occurs when we’re so young. It’s a transition that is analogous to when water freezes to ice.” Professor Savage and colleagues from the University of Texas at Austin, the University of Minnesota, Santa Fe Institute, Imperial College London, and the University of California, Los Angeles conducted the comprehensive statistical analysis, using data from more than 60 sleep studies involving humans and other mammals.
Source: Junyu Cao et al. 2020. Unraveling why we sleep: Quantitative analysis reveals abrupt transition from neural reorganization to repair in early development. Science Advances 6 (38): eaba0398; doi: 10.1126/sciadv.aba0398