Light & Young Children’s Health

A recent study by a research team at the University of Colorado at Boulder suggests even slight exposure to dim light can disrupt a youngster’s sleep. The research found any type of light exposure before bed can impact the production of a hormone called melatonin. Melatonin comes from the pineal gland in the brain and impacts your circadian rhythm, a 24-hour biological clock in charge of regulating when to sleep and when to stay awake.

The research team recruited 36 children between the ages of three to five for a nine-day study where children wore wrist monitors to track their sleep and light exposure at night. The first seven days recorded the children on a stable sleep schedule to normalize their circadian rhythms and adopt a pattern where melatonin levels increase at the same time each evening.

On the eighth day, the team transformed the children’s home into “caves” where they placed black plastic on the windows to dim the lights. They also took saliva samples from each child every half hour starting in the early afternoon until after bedtime to look at when the children’s biological night began and the level of melatonin at that time.

On the last day, every child played a game on a light table one hour before bedtime, in a similar position as someone looking at a lit-up phone or tablet. The light intensity varied from five lux to 5,000 lux (one lux is equivalent to the light from a candle three feet away).

Results show exposure to light suppressed melatonin levels by 70 to 99 percent in comparison to the previous night. Unlike adults, exposure to light made a bigger difference in melatonin suppression than brightness.

Specifically, lights at five to 40 lux — dimmer than the average room — suppressed melatonin by 78 percent. Moreover, melatonin production continued to be delayed for an additional 50 minutes after exposure to light.

“Together, our findings indicate that in preschool-aged children, exposure to light before bedtime, even at low intensities, results in robust and sustained melatonin suppression,” says Lauren Hartstein, a postdoctoral fellow in the Sleep and Development Lab at CU Boulder.

Read the full article here.


Light & Adult Heart Health

Researchers from Northwestern University’s Feinberg School of Medicine have found sleeping in a moderately lit room can potentially harm a person’s cardiometabolic health. The study saw just one night of sleep in a room with moderate ambient light increased nighttime heart rate and spiked insulin resistance in the morning.

This new study recruited 20 healthy young adults and split them into two groups. One group spent two consecutive nights in a sleep laboratory under dim light (less than three lux), while the other group spent one night in dim light and a second night under moderate light levels (a room light at 100 lux).

Daniela Grimaldi, co-first author on the study, said her team saw heightened overnight heart rates in participants exposed to brighter light while they slept. This increased stress on the heart at night could plausibly result in declines in a person’s cardiometabolic health over the long-term, according to Grimaldi.

“We showed your heart rate increases when you sleep in a moderately lit room,” said Grimaldi. “Even though you are asleep, your autonomic nervous system is activated. That’s bad. Usually, your heart rate together with other cardiovascular parameters are lower at night and higher during the day.”

The researchers also saw increased insulin resistance in participants the morning after sleeping under moderate light. Senior author Phyllis Zee said this finding may offer clues to observational studies linking higher rates of diabetes to nighttime light exposure.

Read the full article here.