Preschoolers who watch TV sleep less
May 14, 2019
Science Daily/University of Massachusetts at Amherst
Preschoolers who watch TV sleep significantly less than those who don't, according to new research by University of Massachusetts Amherst neuroscientist Rebecca Spencer and developmental science graduate student Abigail Helm.
More surprising to Spencer, known for her groundbreaking research into the role of naps in children's memory and learning, 36 percent of 3- to 5-year-olds had TVs in their bedroom, and a third of those kids fell asleep with the TV on, often watching stimulating or violent adult programming.
The study, published in Sleep Health, the journal of the National Sleep Foundation, suggests that TV use by young children affects the quality and duration of sleep, measured for the first time by an actigraphic device kids wore like a watch on their wrist. Moreover, while daytime napping was found to increase among the kids who watched the most TV, it did not fully compensate for the lost sleep at night.
"The good news is, this is addressable," says Spencer, referring to the opportunity to educate parents about the new, myth-shattering evidence that TV does not help young children fall asleep. "Parents assumed that TV was helping their kids wind down. But it didn't work. Those kids weren't getting good sleep, and it wasn't helping them fall asleep better. It's good to have this data."
The findings of Spencer and Helm come on the heels of new guidelines from the World Health Organization (WHO), which say children between age 2 and 4 years should have no more than one hour of "sedentary screen time" daily -- and less or no screen time is even better. Similarly, the American Academy of Pediatrics suggests that daily screen time for 2- to 5-year-olds be limited to one hour of "high-quality programs," and that parents should watch the programs with their children. The WHO also emphasized the importance of young children getting "better quality" sleep for their long-term health.
Some 54 percent of kids in the UMass Amherst study are not meeting the WHO's TV-viewing guidelines on weekdays, and the figure jumps to 87 percent on weekends, Spencer says.
In addition to a dearth of data on TV viewing and sleep among this age group, previous research that does exist has relied on parent-reported measures of sleep, and "parents tend to overestimate sleep duration," according to the study. "One of the biggest advantages we have in our approach is the use of these actigraphs," which have been found to provide a reliable measure of sleep, Spencer says.
The new research piggybacked on Spencer's larger study about young children's sleep and cognition, supported by a National Institutes of Health grant. "Given that we already have some data about why sleep and naps are important for young kids, we decided to look into what are the factors that determine when they sleep, how they sleep and why they sleep," Spencer says.
A "very diverse" group of 470 preschoolers from Western Massachusetts participated in the study, wearing actigraphs for up to 16 days. Their parents and caregivers answered questionnaires about demographics and the children's health and behavior, including detailed questions on TV use. Among the findings:
· Preschoolers who watch less than one hour of TV per day get 22 more minutes of sleep at night -- or nearly 2.5 hours per week -- than those who watch more than an hour of TV daily.
· On average, young children without TVs in their bedrooms slept 30 minutes more at night than those with a TV in their bedroom.
· Although kids with TVs in their bedroom slept on average 12 minutes longer during naps, they still slept 17 minutes less during a 24-hour period than kids without TVs in their bedroom.
Spencer says she plans to expand future child sleep studies to examine the impact of hand-held digital devices, such as iPads and smartphones. She also points out that TV use by kids as reported by their parents is likely to be underestimated.
"I think TV is its own beast to understand," she says.
https://www.sciencedaily.com/releases/2019/05/190514110316.htm
Preschoolers exposed to nighttime light lack melatonin
One hour lowers sleep-promoting hormone 88 percent
March 5, 2018
Science Daily/University of Colorado at Boulder
A new study found that preschoolers exposed to bright light at bedtime had an 88 percent reduction in melatonin levels. Anatomical differences in their young eyes may make them more vulnerable to adverse impacts of bright light, the researchers say.
Exposing preschoolers to an hour of bright light before bedtime almost completely shuts down their production of the sleep-promoting hormone melatonin and keeps it suppressed for at least 50 minutes after lights out, according to new University of Colorado Boulder research.
The study, published today in the journal Physiological Reports, is the first to assess the hormonal impact nighttime light exposure can have on young children.
The study comes at a time when use of electronics is rapidly expanding among this age group and adds to a growing body of evidence suggesting that-because of structural differences in their eyes-children may be more vulnerable to the impact light has on sleep and the body clock.
"Although the effects of light are well studied in adults, virtually nothing is known about how evening light exposure affects the physiology, health and development of preschool-aged children," said lead author Lameese Akacem, a CU Boulder instructor and researcher in the Sleep and Development Lab. "In this study we found that these kids were extremely sensitive to light."
For the study, the researchers enrolled 10 healthy children ages 3 to 5 years in a seven-day protocol. On days one through five, the children followed a strict bedtime schedule to normalize their body clocks and settle into a pattern in which their melatonin levels began to go up at about the same time each evening.
On day six, Akacem's team came into the children's homes and created a dim-light environment, covering windows with black plastic and swapping out existing lights with low-wattage bulbs. This ensured that all the children were exposed to the same amount of light-which can influence melatonin timing and levels-before samples were taken.
That afternoon, the researchers took periodic saliva samples to assess melatonin levels at various times. The following evening, after spending the day in what they playfully referred to as "the cave," the children were invited to color or play with magnetic tiles on top of a light table emitting 1,000 lux of light (about the brightness of a bright room) for one hour.
Then the researchers took samples again, comparing them to those taken the night before.
Melatonin levels were 88 percent lower after bright light exposure. Levels remained suppressed at least 50 minutes after the light was shut off.
Direct comparisons between this study and studies in adults must be made with caution because of differing research protocols, the researchers stress. However, they note that in one study, a one-hour light stimulus of 10,000 lux (10 times that of the current study) suppressed melatonin by only 39 percent in adults.
"Light is our brain clock's primary timekeeper," explains senior author Monique LeBourgeois, an associate professor in the Department of Integrative Physiology. "We know younger individuals have larger pupils, and their lenses are more transparent. This heightened sensitivity to light may make them even more susceptible to dysregulation of sleep and the circadian clock."
She explains that when light hits the retina in the eye in the evening, it produces a cascade of signals to the circadian system to suppress melatonin and push back the body's entrance into its "biological night." For preschoolers, this may not only lead to trouble falling asleep one night, but to chronic problems feeling sleepy at bedtime.
Melatonin also plays a role in other bodily processes, regulating temperature, blood pressure and glucose metabolism.
"The effects of light at night exposure can definitely go beyond sleep," Akacem said.
The study sample size was small and it used only one intensity of light, 1,000 lux, which is far greater than the intensity of a typical handheld electronic device, she notes.
With a new $2.4 million grant from the National Institutes of Health, LeBourgeois recently launched a study in which she will expose 90 children to light of different intensities to determine how much it takes to impact the circadian clock.
"The preschool years are a very sensitive time of development during which use of digital media is growing more and more pervasive," Le Bourgeois said. Use of electronic media among young children has tripled since 2011. "We hope this research can help parents and clinicians make informed decisions on children's light exposure."
The takeaway for parents today: Dim the lights in the hours before bedtime.
https://www.sciencedaily.com/releases/2018/03/180305160151.htm