21/03/2025
The four-month regression, everybody agrees on, is the real deal, and it’s permanent.
Many of us just think of sleep as an on-or-off situation. You’re either asleep or you’re not. But sleep actually has a number of different stages, and they make up the “sleep cycle,” which we go through several times a night.
𝗦𝘁𝗮𝗴𝗲 𝟭 is that initial stage we’re all familiar with, where you can just feel yourself drifting off, but don’t really feel like you’ve fallen asleep.
𝗦𝘁𝗮𝗴𝗲 𝟮 which is considered the first “true sleep” stage. This is where people tend to realize, once woken up, that they actually were sleeping. For anyone taking a “power nap,” this is as deep as you want to go, or else you’re going to wake up groggy.
𝗦𝘁𝗮𝗴𝗲 𝟯 is deep and regenerative. Also known as “slow wave” sleep, this is where the body starts repairing and rejuvenating the immune system, muscles tissue, energy stores, and sparks growth and development.
𝗦𝘁𝗮𝗴𝗲 𝟰 is REM (rapid eye movement) sleep. This is where the brain starts to kick in and consolidates information and memories from the day before. It’s also the stage where we do most of our dreaming.
Once we’ve gone through all of the stages, we either wake up or come close to waking up, and then start over again until the alarm goes off.
Newborn babies only have 2 stages of sleep; 𝗦𝘁𝗮𝗴𝗲 𝟯 and 𝗥𝗘𝗠, and they spend about half their sleep in each stage. But at around the third or fourth month, there is a reorganisation of sleep, as they embrace the 4-stage method of sleep that they’ll continue to follow for the rest of their lives.
When this change takes place, baby moves from 50% REM sleep to 25% in order to make room for those first two stages. So although REM sleep is light, it’s not as light as these 2 new stages that they’re getting used to, and with more time spent in lighter sleep, there’s more of a chance that baby’s going to wake up.