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Baby not sleeping through the night at 12 months? Nothing to worry about, study finds

Photo by Bastien Jaillot on Unsplash
A new Canadian study found interrupted sleep had no effect on the babies’ cognitive or physical development.

For decades, the conventional wisdom — including that of most pediatricians — has been that babies should be sleeping through the night by the time they’re 6 months old.

When a baby continues to regularly wake up in the small hours of the morning after that age, parents often feel like a failure. They also worry that their child’s inability to sleep through the night may be a sign of other developmental delays to come.

A new Canadian study, published online Wednesday in the journal Pediatrics, should ease those parental concerns. The study not only found that a high proportion of infants do not sleep through the night by the time they are 6 or even 12 months old, it also found that interrupted sleep had no effect on the babies’ cognitive or physical development.

Furthermore, the study found no evidence that the mothers of babies who aren’t sleeping through the night are at greater risk of depression.

“Our findings suggest parents might benefit from more education about the normal development of — and wide variability in — infants’ sleep-wake cycles instead of only focusing on methods and interventions, especially for those who feel stressed about methods such as delayed response to crying,” said Marie-Helene Pennestri, the study’s lead author and a psychologist at McGill University in Montreal, in a released statement.

The ‘gold standard’

Sleep plays an essential role, of course, in a child’s development, and research has shown that lack of sleep is associated with both physical and mental health problems.

The American Academy of Pediatrics recommends that babies under the age of 12 months get 12 to 16 hours of sleep a day for optimal health.

But that sleep time includes daytime naps. As Pennestri and her co-authors point out in their study, it’s never been clear what the specific contribution of sleeping through the night is to an infant’s health and development.

Despite that lack of evidence, sleeping through the night (usually defined as sleeping for six to eight hours) is widely considered a developmental milestone in an infant’s life, and accomplishing that milestone by age 6 months is deemed the “gold standard” that all parents — at least in Western industrialized nations, such as the United States and Canada — should aim for.

When babies fail to meet that milestone, pediatricians and child-development experts often suggest that parents try various behavioral sleep-training techniques, such as “controlled crying” or “delayed feeding.”

“However, many parents report that these methods are incongruent with their personal beliefs and find sleep interventions too difficult, particularly attempts to ignore infant crying,” write Pennestri and her co-authors.

For those reasons, the researchers decided to investigate whether sleeping through the night in early infancy has any negative effects on either child development or maternal mood.

How the study was done

For their study, Pennestri and her colleagues analyzed data collected from 388 new mothers who were participating in an ongoing Canadian study involving mothers and their children. All the pregnancies of the 388 women were without complications, and both the mothers and the babies had no serious medical conditions.

When the babies were 6 and 12 months of age, the mothers filled out a detailed questionnaire about their baby’s sleeping habits. One of the questions was, “During the night, how many consecutive hours does your child sleep without waking up?”

Trained research assistants went to the families’ homes when the babies were 6, 12 and 36 months old to assess the children’s mental and psychomotor development. During those visits, the mothers filled out a questionnaire specially designed to assess their mood and identify postpartum depression.

Key findings

The analysis of all that data revealed that at 6 months of age, 38 percent of the babies were not yet sleeping at night for at least six consecutive hours, and 57 percent were not sleeping for eight consecutive hours.

At 12 months, 28 percent of the babies were not yet sleeping uninterrupted for six hours, and 43 percent weren’t sleeping for eight straight hours.

Interestingly, the study did reveal a gender difference. At 6 months, for example, a slightly higher percentage of the girls (48 percent) than the boys (39 percent) were sleeping for eight hours straight — a finding consistent with other research, the study’s authors point out.

The study also found no association between sleeping through the night and the children’s mental and psychomotor development (such as when the babies were able to turn over, sit and walk). Nor did it find any link between sleeping through the night and the mood of the mothers.

“This is noteworthy,” write the researchers, “because maternal sleep deprivation is often invoked to support the introduction of early behavioral interventions.”

The study did uncover a strong relationship between breastfeeding and not sleeping through the night. For example, in the group of infants who slept through the night at six months, only 24 percent were breastfed.

Pennestri and her colleagues stress, however, that this finding does not mean that breastfeeding causes infants to have more interrupted sleep. They also point out that breastfeeding offers babies — and mothers — many important health benefits, which is why health experts recommend that mothers exclusively breastfeed their babies for the first 6 months of age and then partially breastfeed for up to 2 years — or as long as the mother and baby both want.

A better, if not longer, night’s sleep

The study comes with caveats. Most notably, it was a relatively small study, and it relied on the mothers’ reports about their child’s sleep habits instead of directly monitoring the babies as they slept.

Still, the study suggests that it may be time to moderate our expectations for when babies should start sleeping through the night.

“The transition to parenthood is a vulnerable period of life,” write Pennestri and her colleagues, “and it could be reassuring for parents to learn that in a typically developing cohort up to 37.6% of infants do not sleep 6 consecutive hours at age 6 months and up to 27.9% do not at age 12 months.”

That knowledge could also help new parents sleep … well, not necessarily longer at night, but with a lot less stress and worry.

FMI: You’ll find the study on the Pediatrics website.

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Comments (2)

  1. Submitted by Ray Schoch on 11/15/2018 - 09:43 am.

    As an infant, my son did not sleep for more than 2 or 3 hours at a time for months. His sleep-deprived parents alternated who would get up at whatever unreasonable hour it was, to tend to him. He seems to have turned out OK, decades later.

    His first child, in turn, didn’t sleep for more than a couple hours at a time for months, and was a **very** unhappy infant. Then, more or less like turning on the light switch, the pattern flipped to sleeping 6 or more hours. The baby’s mood did not immediately transform itself, but it did improve, and years later, at age 9, she’s a healthy, happy little girl.

    His second child routinely slept in 4 to 6-hour chunks from the beginning, and began to sleep through the night after only a few weeks. On the other hand, he wakes up at the first hint of daylight on the horizon, unlike the rest of his family.

    Both children were nursed beyond 6 months, though I don’t remember exactly how long. In any case, and for what it’s worth from an old guy, I do think any expectation that an infant will sleep through the night right away is fairly unrealistic. Those middle-of-the-night adventures are part of the “joys of parenthood” that provide many entertaining stories told in later years over a meal or during a celebration.

  2. Submitted by Solly Johnson on 11/15/2018 - 09:21 pm.

    My two children never slept through the night until they were about 18 months old. Every morning about 1 or 2 a.m. they would wake up for a drink of water and then go back to sleep. My wife and I never gave consideration to any studies about our children being developmental delayed, only that they were thirsty and wanted a drink. Both were happy children, performed very well in school, and now hold professional positions.

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