If your little night owl suddenly can't get enough sleep, don't worry, say sleep scientists, it's probably just a growth spurt. According to a study that proves grandma was right all along when she told you babies wake up taller after a good night's sleep, researchers from Emory University have found that growth spurts are tied to an increase in total daily hours of sleep as well as an increase in the number of naps or "sleep episodes."
In the study, researchers had 23 moms keep daily sleep records for their infants (14 girls, nine boys). Over a period of 17 months, sleep logs revealed that all babies periodically experienced uneven bursts of sleep, with total amounts of snooze time increasing by an average of 4.5 hours per day for two days—and then returning to normal. During this time, the number of sleep episodes also increased in surges of up to three extra naps per day for two days.
Tracking body growth, it was immediately clear that growth spurts tended to occur within 48 hours of these sleep bursts. Researchers determined that the likelihood of a growth spurt increased by about 43 percent for each additional sleep episode and by 20 percent for each extra hour of sleep. The study also showed differences in growth spurt sleep patterns depending on the sex of the baby. In general, boys in the study exhibited more sleep bouts and shorter sleep bouts than girls.
So why is science concerned about something that just seems like common sense? Practically speaking, studies like this one can help parents understand that irregular sleep behavior is a normal part of growth and development.
"Sleep irregularities can be distressing to parents," says Dr. Michelle Lampl, Samuel C. Dobbs professor of anthropology, Emory University, associate director, Emory/Georgia Tech Predictive Health Institute and lead author of the study. "However, these findings give babies a voice that helps parents understand them and show that seemingly erratic sleep behavior is a normal part of development."
What's normal when it comes to Baby's sleep? Expect your newborn to snooze as much as 16 hours a day (or even more), often in stretches of three to four hours at a time, say experts from the Nemours Children's Health Foundation. During a growth spurt, this may mean your newborn gets upwards of 20 hours of shut eye per day, likely spread out over a series of naps during the day and a longer stretch of nighttime sleep.
And like the sleep all of us experience, babies have different phases of sleep: drowsiness, REM (rapid eye movement) sleep, light sleep, deep sleep, and very deep sleep. Researchers speculate that certain sleep phases may stimulate growth hormone production in babies, a key reason why it is so important for parents to let babies call the shots when it comes to how long and how much sleep they need.