Doc, When Is My Baby Going to Start Sleeping through the Night?

Why do some infants sleep through the night as early as two months of age, when others can take up to as long as 12 months? It's a question that has been posed by many, including both pediatricians and parents.

Most infants meet the conventional definitions for sleeping through the night by 12 months of age; however, little is known about the changes in infants’ self-regulated sleep, as judged by developmentally and socially valid criteria for sleeping through the night. A new study published in Pediatrics examined sleep-regulation capabilities by comparing three criteria for sleeping through the night, and unearthed some interesting results that may alter the advice pediatricians provide for new parents.

In the study, a team of researchers from the University of Canterbury in New Zealand investigated consolidation of self-regulated nocturnal sleep over the first year, utilizing longitudinal data to provide an empirical foundation for infants’ self-regulated sleep. Parents of 75 normally developing infants completed sleep diaries for six days each month for 12 months; a video recorder was used to verify accuracy.

To qualify as sleeping through the night, an infant had to meet the following criteria for five of six nights of the week (or 80% of the time if there was missing data):

• Criteria 1: Sleeping uninterrupted from midnight to 5 a.m.
• Criteria 2: 8-hour criterion (sleeping uninterrupted for 8 hours minimum between sleep onset and time awake in the morning)
• Criteria 3: Family-congruent criterion, sleeping uninterrupted from 10 p.m. to 6 a.m.

Researchers determined that the largest mean increase (504 minutes) in self-regulated sleep length occurred from one to four months. The age at which most infants met criteria 1 was two months, criteria 2 was three months, and criteria 3 was four months. A 50% probability of meeting criteria 1 and 2 occurred at three months and at five months for criterion 3, they found. The hazard function identified two months (criteria 1 and 2) and three months (criterion 3) as the most likely ages for sleeping through the night. At 12 months, 11 infants did not meet criteria 1 or 2, whereas 21 failed to meet criterion 3.

The most rapid consolidation in infant sleep regulation was found to occur in the first four months, they concluded, and most infants are sleeping through the night at two and three months, regardless of the criterion used. The most developmentally and socially valid criterion for sleeping through is from 10 p.m. to 6 a.m. At five months, more than half of infants are sleeping concurrently with their parents.

“Our longitudinal data provide a reliable empirical foundation for advice about infant sleep development and provide a context for clinicians to discuss sleep issues with parents,” investigators wrote. “Prevention efforts should focus in the first 3 months, beginning as early as 1 month for intervention to be synchronous with the onset of sleeping through the night. Additional research is now needed to establish the factors that precede and predict infant sleep problems.”

To access the Pediatrics study, click here.

What have you found in your practice in terms of infant sleep-regulation capabilities? Will these findings impact the advice you provide for parents of infants?