Infant Growth Spurts Tied to More Sleep

May 2, 2011 -- It has often been thought that an infant’s sleeping patterns are related to his or her growth, but this theory was never documented until now.

New research in the May 1 issue of Sleep shows that an increase in the number of sessions of sleep, as well as an increase in total daily hours of sleep, likely means that an infant is experiencing a growth spurt.

“The results demonstrate empirically that growth spurts not only occur during sleep but are significantly influenced by sleep [and] longer sleep [equals] greater growth in body length,” says study researcher Michelle Lampi, MD, PhD, the Samuel Candler Dobbs Professor in the department of anthropology at Emory University in Atlanta, in an email.

In the new study, 23 sets of parents of newborns kept daily sleep records. Infant sleep time was compared with growth in length for durations ranging from four to 17 months.

Growth spurts in length tended to follow increased sleeping and nap time. Growth spurts usually occurred within two days of the increased sleep, the study showed.

Specifically, the chances of a growth spurt increased by a median of 43% for each nap and by increased by 20% for each additional hour of sleep.

Exactly how sleep and growth are interrelated is not fully understood.

“Measurable growth followed sleep, [but] it is possible that another mechanism controlling growth acts through alterations in sleep,” Lampi says.

Infants Need Sleep to Grow

The new findings make intuitive sense, says sleep expert Michael Breus, PhD, author of several books including Beauty Sleep.

Infants sleep differently than adults, he says. “Almost no sleep in an infant is considered light sleep,” he says. Growth hormone is produced during the deeper stages of sleep.

“This is the first study to actually show a relationship between sleep time and growth spurts, and it reiterates that infants and children need high-quality sleep,” Breus says.

Infants' and children's bedtimes should be set in stone, he says. “Some parents may wait until the other parent gets home to put their child to bed, but if it’s past the child’s bedtime, they need to go to bed,” he says.

There is no scientific evidence to suggest that children who don’t get enough sleep don’t grow as much, but anecdotally “you do see children who are not good sleepers who don’t grow as quickly,” he says.

“The new study exemplifies the importance of sleep,” he says. “You need sleep to grow both physically and mentally.”