Parents already know that letting children stay up too late can lead to rough mornings or trouble at school. But new Clemson University research suggests the effects might go deeper than that, possibly all the way down to a child’s genes.
A recent study, “Epigenetic Impact of Sleep Timing in Children,” by a team of scientists led by Geetha Thangiah, a professor in the Department of Food, Nutrition and Packaging Sciences, found that children who regularly go to sleep later may exhibit subtle changes in the function of certain genes. These changes don’t alter the DNA but affect how the genes are turned on or off, or expressed, influencing brain development, metabolism and overall health over time.
“This isn’t just about children feeling tired the next day,” said Erika Richter, a Clemson doctoral candidate and scientist on the study. “We’re seeing signs that sleep timing could actually influence how a child’s body develops at a molecular level.”
Richter plans to graduate in August. She will continue her postdoctoral studies at Columbia University.
What the scientists looked at
The study focused on children aged 6 to 10. The scientists compared children who tended to go to sleep early, before 8:30 p.m., with those who went to sleep after 8:30 p.m. They collected saliva samples and examined epigenetic changes via DNA methylation, a chemical marker that helps determine gene function.
They found differences at more than 1,000 sites across the DNA samples, affecting hundreds of genes. Many of these genes are linked to important processes within the body related to brain activity, metabolism and stress response.
Some of the main systems involved included:
- The body’s internal clock (circadian rhythm)
- Brain development and signaling
- Hormonal and insulin regulation
- Stress and immune responses
In other words, it’s not just how long children sleep that matters. Timing also seems to play a role.
The American Academy of Sleep Medicine recommends that children get the following amounts of sleep every 24 hours:
- 10–13 hours for ages 3–5
- 9–12 hours for ages 6–12
- 8–10 hours for teens
Why timing matters
Scientists have known for a while that poor sleep is linked to issues like anxiety, weight gain and learning problems in children. What this study adds is a possible explanation for why, showing how those effects might begin at a biological level.
“These epigenetic changes are like dimmer switches for genes,” Thangiah said. “Going to sleep later might be nudging certain systems slightly off balance.”
That doesn’t mean going to sleep later will automatically cause health problems. But it suggests that sleep habits could have a longer-lasting impact than previously thought.
Looking at the bigger picture
Childhood is a time when the body is especially sensitive to outside influences. Sleep is a big one. Because these epigenetic patterns can stick around, the scientists believe they might help explain links between early sleep habits and risks, such as:
- Obesity or metabolic issues
- Learning or cognitive challenges
- Mental health concerns
“Sleep is one of the few things we can realistically improve with relatively simple changes,” Richter said. “That’s what makes this important. Small adjustments could make a real difference over time.”
Consistency over perfection
The scientists aren’t saying every child needs the same bedtime. But they do emphasize consistency. Going to bed roughly the same time each night, in sync with natural sleep rhythms, seems to support healthier overall development.
With screens, homework and busy schedules, perfect routines aren’t always possible. Still, the scientists say that taking small steps toward a more regular sleep schedule could have benefits that go well beyond just making mornings easier.
For more information, read Epigenetic Impact of Sleep Timing in Children: Novel DNA Methylation Signatures via SWAG Analysis,” in the October 2025 edition of the International Journal of Molecular Sciences.
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