Sleep and heart health are national concerns in the U.S., where high blood pressure affects nearly half of adults, according to federal health agencies. A new research finding narrows that focus to one common habit: sleeping with the lights on.
What the study found
Scientists at Northwestern University reported on March 14, 2022, that sleeping with moderate room light was linked to higher nighttime blood pressure and heart rate in healthy adults. The study, published in the Proceedings of the National Academy of Sciences, included 20 people who spent 2 nights in a sleep laboratory.
On one night, participants slept in dim light. On the other, they slept with overhead room light on. The researchers said the brighter light condition was about 100 lux, a level similar to a cloudy day indoors.
The team found that after just 1 night of sleeping with room light, participants had higher heart rates during sleep and showed signs of increased insulin resistance the next morning. The researchers also reported that blood pressure stayed higher overnight, rather than dropping as much as it normally does during sleep.
What it means in everyday life
The study did not test every type of light people use at home. Researchers specifically examined indoor room light in a lab setting, so the results do not confirm the same effect for a TV, a phone screen, or a hallway night-light.
What is confirmed is that even 1 night of moderate light changed measurable cardiovascular markers in the 20-person study. The researchers said the body remains on alert with light exposure at night, which may affect the autonomic nervous system during sleep.
For U.S. households, that makes this finding especially relevant because many people sleep with a lamp, television, or other light source nearby. The study did not release state-by-state data, and it did not track long-term blood pressure outcomes outside the lab.
Why researchers think this happens
The Northwestern team said nighttime light may disrupt the body’s normal sleep-related recovery processes. During healthy sleep, blood pressure usually dips, but in the bright-room condition, that decline was reduced, according to the study.
Researchers also pointed to the role of the autonomic nervous system, which controls heart rate and other automatic functions. In the light-on condition, the body appeared less able to fully rest, even though participants were asleep for the night.
For readers, the practical takeaway is narrow and factual: this study connected moderate light during sleep with higher nighttime blood pressure after 1 night in a lab. The researchers said avoiding or dimming room light at bedtime may help support normal overnight cardiovascular function, while more research is still needed on long-term effects.
