Study finds light exposure during sleep may affect heart healthUpdated: 1:06 PM EDT Sep 10, 2026 Editorial Standards ⓘ CNNA new study suggests that exposure to light during sleep, even at low levels, may negatively impact heart health.
Related video: Sleep hacks, simple tips for the best restAdvertisementResearchers analyzed the sleep patterns of more than 11,000 people without heart disease.
Participants wore wrist sensors for seven days to measure light levels throughout the night.
During the study, authors found that individuals exposed to light levels of more than 3 lux experienced changes in the shape and function of their heart muscles compared with those who had no light exposure at night.
Experts not involved in the study noted its limitations, including the duration of testing and the use of light sensors.
Study finds light exposure during sleep may affect heart health
Updated: 1:06 PM EDT Sep 10, 2026 Editorial Standards ⓘ CNN
A new study suggests that exposure to light during sleep, even at low levels, may negatively impact heart health.
Related video: Sleep hacks, simple tips for the best rest
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Researchers analyzed the sleep patterns of more than 11,000 people without heart disease. Participants wore wrist sensors for seven days to measure light levels throughout the night.
Three years later, they underwent cardiac MRIs to examine their heart structure and function.
During the study, authors found that individuals exposed to light levels of more than 3 lux experienced changes in the shape and function of their heart muscles compared with those who had no light exposure at night. Three lux is roughly equivalent to moonlight or light bleeding under a closed bedroom door.
Experts not involved in the study noted its limitations, including the duration of testing and the use of light sensors. They emphasized the need for further research.
The study was published Wednesday in the European Heart Journal.
