Grandma was right: Infants do wake up taller

May 1, 2011

Science is finally confirming what grandma knew all along: infants wake up taller right after they sleep.

Findings from the first study of its kind measuring the link between daily growth and sleep show the two are inextricably linked. Specifically, growth spurts are tied to an increase in total daily hours of sleep as well as an increase in the number of daily sleep bouts, the time from the onset of sleep until awakening.

"Little is known about the biology of growth spurts," says Michelle Lampl, MD, PhD, Samuel C. Dobbs professor of anthropology, Emory University, associate director, Emory/Georgia Tech Predictive Health Institute and lead author of the study. "Our data open the window to further scientific study of the mechanisms and pathways that underlie saltatory growth."

Practically speaking, however, the study helps parents understand that irregular sleep behavior is a normal part of growth and development.

"Sleep irregularities can be distressing to parents," says Lampl. "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. Babies really aren't trying to be difficult."

Lampl's study appears in the May 1 issue of Sleep and is co-authored by Michael Johnson, PhD, professor of pharmacology, University of Virginia Health System.

The researchers also found that longer sleep bouts in both girls and boys predicted an increase in weight and body-fat composition tied to an increase in length. In other words, not only does sleep predict a growth spurt in length, but it also predicts an increase in weight and abdominal fat, implying an anabolic process—growth.

What's more, the study showed differences in sleep patterns related to growth depending on the sex of the baby. "Growth spurts were associated with increased sleep bout duration in boys compared with girls and increased number of sleep bouts in girls compared with boys," says Lampl.

In general, boys in the study exhibited more sleep bouts and shorter sleep bouts than girls. But neither the sex of the infant nor breastfeeding had significant effects on total daily sleep time. However, breastfeeding as opposed to formula feeding was associated with more and shorter sleep bouts.

Unlike previous studies, this study did not rely on parental recall of infant sleep patterns and growth. Instead, data on 23 were recorded in real time over a four- to 17-month span. Mothers kept daily diaries detailing onset and awakening and noted whether babies were breastfeeding, formula feeding, or both and whether their infant showed signs of illness, such as vomiting, diarrhea, fever or rash.

Related Stories

Recommended for you

Why sugary drinks and protein-rich meals don't go well together

July 20, 2017
Having a sugar-sweetened drink with a high-protein meal may negatively affect energy balance, alter food preferences and cause the body to store more fat, according to a study published in the open access journal BMC Nutrition.

Opioids and obesity, not 'despair deaths,' raising mortality rates for white Americans

July 20, 2017
Drug-related deaths among middle-aged white men increased more than 25-fold between 1980 and 2014, with the bulk of that spike occurring since the mid-1990s when addictive prescription opioids became broadly available, according ...

Aging Americans enjoy longer life, better health when avoiding three risky behaviors

July 20, 2017
We've heard it before from our doctors and other health experts: Keep your weight down, don't smoke and cut back on the alcohol if you want to live longer.

Parents have critical role in preventing teen drinking

July 20, 2017
Fewer teenagers are drinking alcohol but more needs to be done to curb the drinking habits of Australian school students, based on the findings of the latest study by Adelaide researchers.

Fresh fish oil lowers diabetes risk in rat offspring

July 19, 2017
Fresh fish oil given to overweight pregnant rats prevented their offspring from developing a major diabetes risk factor, Auckland researchers have found.

High-dose vitamin D doesn't appear to reduce the winter sniffles for children

July 18, 2017
Giving children high doses of vitamin D doesn't appear to reduce the winter sniffles, a new study has found.

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

LuckyBrandon
1 / 5 (1) May 01, 2011
ok this is known fact, and it applies to everybody, not just infants, because our spines compress throughout our day as we sit up and stand/walk.
we were taught this in the army over a decade ago, and its why we took height measurements in the morning (there could be up to a 1 inch variation between 6-7am and 6-7pm).
id say they're a little late on this study.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.