Ask the doctors: Temporary use of night-lights doesn’t harm children

Q: It is my understanding that one should sleep in a dark, cool room. At what age does it become a problem for children who have slept with night-lights and have been bundled up since birth? Do night-lights tell children that the dark is something to be afraid of?

A: You are correct about the new understanding regarding optimal conditions for a good night's sleep. They include a comfortable and yet supportive surface for your body, a quiet environment, a moderate room temperature in the mid-60s to low-70s, and no ambient light.

This may sound like a finicky to-do list, but our nightly recharge is important. High-quality sleep not only sets you up for the tasks and challenges of the coming day, but it plays a key role in physical, mental and emotional health.

When it comes to the effects of ambient light on the sleep of children, you have actually posed two different and very interesting questions. One focuses on the physiology of light exposure on sleep systems that are still in the developmental stage. The other asks what effect the protection of a night-light might have on a child's response to darkness.

Here in the United States, night-lights have long been a fixture of childhood bedrooms. But as we understand more about sleep physiology, it's reasonable to wonder how they help or hurt. This is particularly true because of what we're learning from research on circadian development.

It is important to understand that, in children, the circadian systems that wire the human body to the Earth's cycle of light and dark are still developing. The daily shifts from light to dark and back again trigger complex hormonal shifts. These shifts are calibrating young brains and bodies. That means light at nighttime — even the soft glow of a stuffed animal friend — can nudge that timing. It can shift the biological sense of when sleep should begin.

Research has shown that even a small amount of nighttime light can delay the internal sleep signal. This doesn't mean night-lights have to be banished, but it's a useful piece of information for managing children's sleep. You can always plan for a transition to a darker room in the future.

That brings us to your second question. Fear of the dark is natural and nearly universal in human development. It can begin as early as age 2 or 3, as memory forms and imagination grows. It usually peaks between ages 3 and 6. Brain development, parent reassurance and normal life experience work together to gradually resolve it.

While a night-light can ease a fear of the dark, it's not likely to cause it. What does matter is whether the light becomes a permanent fixture. If they never have darkness, a child can't make the important discovery that their room is just as safe without a light on.

The bottom line is that night-lights are not harmful for children. What matters is that they are used as a temporary bridge, and not a permanent crutch.

• Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu.

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