⁍ Researchers conducted a statistical analysis on data from more than 60 sleep studies.

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⁍ They looked at sleep time, duration of rapid eye movement sleep, brain size and body size.

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⁍ They devised a mathematical model for how sleep changes during development.

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– At 2.4 years of age, the brain’s primary function shifts from building and cutting connections during rapid eye movement (REM) sleep to neural repair during both REM and non-REM sleep, according to a study published Friday in Science Advances. “It was shocking to us that this transition was like a switch and so sharp,” UCLA professor of ecology and evolutionary biology David Van Savage tells Reuters. REM sleep is deep sleep with vivid dreams. Non-REM sleep is largely dreamless. During REM sleep, the brain forms new neural connections by building and strengthening synapses—the junctions between nerve cells, or neurons—that enable them to communicate, reinforcing learning and consolidating memories. During sleep, the brain also repairs the modicum of daily neurological damage it typically experiences to genes and proteins within neurons as well as clearing out byproducts that build up. At about 2.4 years of age, the findings showed, sleep’s primary function changed from building and cutting connections during REM sleep to neural repair during both REM and non-REM sleep. Van Savage says sleep “is required across the animal kingdom and is nearly as ubiquitous as eating and breathing. I’d say it is a pillar of human health.’