“Infants are capable of resettling themselves back to sleep by three months of age,” according to the study by Ian St James-Roberts and colleagues of the University of London. They add, “Both autonomous resettling and prolonged sleeping are involved in ‘sleeping through the night’ at an early age.”
Videos show what goes on when babies sleep through the night
Dr St James-Roberts and colleagues used infrared video cameras to make overnight recordings of 101 London infants. Videos made at five weeks and three months of age were analyzed to determine changes in sleep and waking during this age span — a time when parents hope their baby will start sleeping more at night, while crying less.
The researchers also looked for times when the infants woke up but were able to “resettle autonomously” — to go back to sleep without parental involvement. The video evidence was compared with parental questionnaires on their infants’ sleep behaviors.
The “clearest developmental progression” between video recordings was an increase in length of sleeps: from a little over 2 hours at five weeks to 3.5 hours at three months. Only about ten percent of infants slept continuously for 5 hours or more at five weeks, compared to 45 percent at three months.
At both ages, about one-fourth of infants awoke and resettled themselves–without parental contact — at least once during the night. These infants were able to go back to sleep with little or no crying/fussing. (An online video shows a three-month-old baby waking and resettling.)
“Self-resettling at five weeks predicted prolonged sleeping at three months,” the researchers write. Sixty-seven percent of infants who resettled in the first recording slept continuously for at least 5 hours in the second recording, compared to 38 percent who didn’t resettle.
Infants were more likely to suck their fingers or hands at three months compared to five weeks. Infants who slept through the night at three months spent more time sucking their fingers or hands–a “self-regulatory” strategy that may help them initiate or maintain sleep.
No difference between breasfed and formula-fed babies
Previous studies have suggested that breastfed infants wake up at night because they need to feed frequently. However, the new results showed no difference in resettling or sleep times for infants fed breastmilk versus formula.
Waking up and crying at night is the most common type of infant sleep problem, and one that causes exhaustion and strain for parents. Previous video studies have shown that what parents call ‘sleeping through the night’ is a misnomer — older babies who ‘sleep through the night’ not only sleep for longer periods, but also have the ability to resettle themselves after waking.
The new study confirms that some infants develop this resettling ability in the first three months of age. “Findings indicate the need for studies of how arousal, waking and resettling develop into sustained sleeping, and of how environmental factors support these endogenous and behavioral processes,” says Dr St James-Roberts.
“If they fulfill their promise, the findings may eventually help to resolve the puzzle of why so many healthy infants should be diagnosed with sleep problems, as well as helping the families involved.”