Cribsheet: A Data-Driven Guide to Better, More Relaxed Parenting, from Birth to Preschool (The ParentData Book 2)

by Emily Oster

The study strongly supported the value of swaddling for sleep. While swaddled, the babies slept longer overall, with more time spent in REM sleep. This paper also identified the mechanism: swaddling improves sleep because it limits arousals.3 Swaddled babies are equally likely to have the first stage in arousal—measured with baby “sighs”—but are less likely to move from this to the second stage (“startles”) or the third (“fully awake”). Something about the swaddle discourages these second and third stages. These effects are big. The study found that when babies were not swaddled, a sigh turned into a startle 50 percent of the time. When they were swaddled, this occurred only 20 percent of the time. This type of laboratory evidence is confirmed by observational data and descriptive studies.