Nighttime light exposure linked to heart disease
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- Reviewed by Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
Higher exposure to light at night between 12:30 a.m. and 6 a.m. is linked to an increased risk of cardiovascular problems, according to a study in the Oct. 1, 2025, issue of JAMA Network Open.
The study included nearly 89,000 people ages 41 and older who wore light sensors on their wrists for one week. Researchers then tracked their risk of heart disease over the following 9.5 years. People with the highest exposure to nighttime light had higher risks of coronary artery disease, stroke, atrial fibrillation, heart attack, and heart failure. These associations held even after the researchers adjusted for other common heart-related risks (such as smoking or high blood pressure) and sleep-related factors (such as when and how long the participants typically slept).
The explanation for these observations isn’t completely clear. But nighttime light exposure may disrupt sleep as well as the body’s circadian rhythm, both of which can influence cardiovascular risk.
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About the Author
Julie Corliss, Executive Editor, Harvard Heart Letter
About the Reviewer
Robert H. Shmerling, MD, Senior Faculty Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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