BoneScience Research Notes · Last reviewed: 2026-10 · General information, not medical advice
- The body's biggest burst of growth hormone comes soon after a child falls into deep sleep.
- Kids 6 to 12 need 9 to 12 hours of sleep. Teens need 8 to 10.
- No study has shown that extra sleep makes a healthy child taller. Sleep is about health, mood and focus.
What happens after lights-out
Growth hormone is a signal the body makes to help it grow and repair. It is not made at a steady rate. It comes out in bursts.
In 1968, a team took small blood samples every 30 minutes all night. They also tracked brain waves. The group was eight young adults.
In seven of the eight, a big burst of growth hormone came right as deep sleep began. Deep sleep is the heavy, hard-to-wake-up kind of sleep. The burst lasted 1.5 to 3.5 hours.
When sleep started later, the burst came later too. When people were woken up and then fell back asleep, a second burst came.
A drawing of the pattern, not one person's data. Based on Takahashi 1968 and Van Cauter 1998, which studied adults.
A 1998 review in the journal Sleep looked at many more studies. It found the same thing. The biggest burst usually comes with the first deep sleep of the night. In men, about 70% of the day's growth hormone comes out early in sleep.
The burst follows sleep, not the clock. Move bedtime, and the burst moves with it. Waking up tends to slow it down.
How much sleep is enough?
In 2016, 13 sleep experts from the American Academy of Sleep Medicine looked at the research. They agreed on these amounts, per 24 hours, on most days:
| Age | Sleep needed |
|---|---|
| 6 to 12 years | 9 to 12 hours |
| 13 to 18 years | 8 to 10 hours |
The experts said kids who often sleep less than this tend to have more trouble with focus, behavior and school. They also have more accidents and higher risk of weight gain and low mood.
Here is an easy way to use the table. Count back from wake-up time. A 12-year-old who gets up at 6:30 a.m. should be asleep by about 9:30 p.m. That gives 9 hours.
What the research doesn't say
It is easy to think, "More sleep means more growth." The research does not show that. Here is why.
First, the hormone studies were small. They were done in adults, and they measured blood, not growth.
Second, a team in Zurich followed 305 healthy kids from age 1 to 10. Each year they measured height and weight and asked about sleep. They found no link between how long kids slept and how they grew. Not at any age.
Third, sleep needs differ from child to child. They also change from year to year. The Zurich team said to fit sleep to each child's own needs.
So sleep matters a lot for a growing child. But it matters for health, mood and focus. It is not a way to add height.
What this research says / doesn't say
Says: The biggest burst of growth hormone comes with the first deep sleep. Kids 6 to 12 need 9 to 12 hours. Teens need 8 to 10. Short sleep is linked to trouble with focus, mood and health.
Doesn't say: That extra sleep makes a healthy child taller. The hormone studies were small and done in adults. A 10-year study of 305 kids found no link between sleep length and growth.
The easiest fix: phones out of the bedroom
This step has good research behind it. A 2016 review in JAMA Pediatrics pooled 20 studies with 125,198 kids. Their average age was 14½.
Kids who used a phone or tablet at bedtime were about twice as likely to sleep too little. Even a phone in the room, not being used, was linked to shorter sleep.
These studies can't prove that phones cause poor sleep. Tired kids may also reach for their phones more. Still, the authors' advice was clear: keep devices out of the bedroom at night.
Three things to try this week
- Set a lights-out time. Count back 9 hours (ages 6 to 12) or 8 hours (teens) from wake-up. Keep it the same most nights.
- Protect the first hours of sleep. That is when deep sleep is strongest. Keep the room dark and quiet.
- Charge phones outside the bedroom. Make it a family rule so no one feels singled out.
Sources
- Takahashi Y, Kipnis DM, Daughaday WH. Growth hormone secretion during sleep. J Clin Invest. 1968;47(9):2079-2090. doi:10.1172/JCI105893
- Van Cauter E, Plat L, Copinschi G. Interrelations between sleep and the somatotropic axis. Sleep. 1998;21(6):553-566. PubMed 9779515
- Paruthi S, et al. Recommended amount of sleep for pediatric populations: a consensus statement of the American Academy of Sleep Medicine. J Clin Sleep Med. 2016;12(6):785-786. doi:10.5664/jcsm.5866
- Jenni OG, Molinari L, Caflisch JA, Largo RH. Sleep duration from ages 1 to 10 years: variability and stability in comparison with growth. Pediatrics. 2007;120(4):e769-e776. doi:10.1542/peds.2006-3300
- Carter B, et al. Association between portable screen-based media device access or use and sleep outcomes: a systematic review and meta-analysis. JAMA Pediatr. 2016;170(12):1202-1208. doi:10.1001/jamapediatrics.2016.2341
This article is general information, not medical advice. If you are worried about your child's sleep or growth, talk with your pediatrician.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
BoneScience makes Dr's Grow UP, an AM/PM daily nutrition system for ages 10+, NSF Certified for Sport®.
The studies above were not conducted on BoneScience products.
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