Sleeping With the TV or a Light On?What Studies Show
Sleep & NighttimeArticleFalling asleep to the TV is a habit for many women. In the US Sister Study of 43,722 women, those who slept with a TV or light on in the room were about a third more likely to develop obesity over about 6 years than those who slept in the dark, even after accounting for sleep length, diet and exercise. A lab study found one night with a room light on raised heart rate and next-morning insulin resistance. Here is what that means.
In this article
Plenty of women fall asleep with the TV murmuring or a lamp still on. It feels harmless, even comforting. Two kinds of research suggest it may be worth switching off.
The Sister Study
US government researchers asked 43,722 women aged 35 to 74 how much light was in their bedroom while they slept: none, a small nightlight, light from outside the room, or a light or TV on in the room.1 They followed the women for about 6 years.1
Compared with sleeping in the dark, women who slept with a TV or light on in the room were:1
| Outcome | Compared with a dark room |
|---|---|
| Gaining 5 kg (11 lb) or more | About 17% more likely1 |
| Developing obesity | About 33% more likely1 |
The link held after accounting for sleep length and quality, diet and exercise.1 It’s an observational study, so it can’t prove the light caused weight gain, but it ruled out several obvious explanations.
One night in the lab
At Northwestern University, healthy adults slept one night in a dimly lit room and one night with a moderately bright light on.2 With the light on, their heart rate was higher overnight and their bodies handled sugar less well the next morning, with higher insulin resistance.2
That’s a short-term change, but it suggests a way light during sleep could affect the body.
What to do
UK sleep advice is to keep the bedroom dark and quiet, using curtains, blinds or an eye mask if needed, and to avoid TV and phones right before bed.3
- Switch off the TV and room lights when you settle down to sleep.
- Block outside light with curtains or a mask.3 See does a sleep eye mask help?
See sleeping with a light on in older age and why you can’t fall asleep at night.
Try: “I can only fall asleep with the TV on, but I wake up tired. What can I try instead, and could this be insomnia?”
Did I Do That in My Sleep? covers evening screens and light in Chapter 10, “In Bed All Night, Tired All Day,” in a section called “Light, Screens and a Usable Routine.” Its 14-Night Lights-Out Record keeps a rough morning account of each night, so you can see whether a darker room makes a difference. See the book.
This article is for general educational purposes only and is not medical advice. It isn't a substitute for diagnosis or treatment from a qualified healthcare professional who knows your health history. Keep a low light available for safe night-time trips to the bathroom, especially if you're at risk of falls. See a doctor if poor sleep lasts for months or affects your days. Girl Playbook does not endorse any specific product, test, or provider.
Girl Playbook sells this book. It provides education and worksheets, not individualized medical care.
Sources
The research behind this article, in the order it’s cited. How we source our articles.
- JAMA Internal Medicine journal (abstract via PubMed), 2019Association of Exposure to Artificial Light at Night While Sleeping With Risk of Obesity in Women (opens in a new tab)abcdef
- Proceedings of the National Academy of Sciences (via PubMed Central), 2022Light exposure during sleep impairs cardiometabolic function (opens in a new tab)ab
- NHS, 2026Insomnia (opens in a new tab)ab
Spotted something out of date? Tell us and we’ll check it.
