A new study led by Flinders University and published inJAMA Network Openreveals that exposure to bright light at night significantly increases the risk of serious heart conditions likeheart attacks,strokes, andheart failure. This groundbreaking research is the largest of its kind, tracking personal light exposure of nearly 89,000 UK adults using wrist-worn sensors over 13 million hours, and following them for up to 9.5 years. Bright light exposure at night disrupts the body’s natural circadian rhythm, increasing the risk of serious heart problems such as heart attacks, strokes, and heart failure. This disruption leads to metabolic and vascular changes that elevate cardiovascular risk independently of other lifestyle factors. Research shows that people exposed to the brightest nighttime light have a significantly higher chance ofheart disease, with women and younger individuals being especially vulnerable. Limiting nighttime light exposure by dimming lights and avoiding screens can protectheart health. The study highlights how disrupting the body’s internal circadian clock by exposure to bright light during normal dark hours raises cardiovascular risk independently of factors like exercise, diet, sleep, and genetics. People exposed to the brightest night light had a 56% higher chance of heart failure and a 47% greater risk of heart attack. Notably, women and younger participants were more vulnerable, with women’s risk equalizing to men’s despite typically lower heart disease rates. Methodologically, participants wore light sensors continuously, allowing precise measurement of indoor and outdoor light exposure reflecting real-world conditions. This approach surpasses prior studies relying on satellite data or subjective reports. Researchers used multivariate analyses adjusting for lifestyle and genetic confounders to isolate the effect of nighttime light exposure on cardiovascular outcomes. Dr. Daniel Windred, lead author, emphasized the importance of mitigating nighttime light exposure through practical measures like blackout curtains and reducing screen time before bed. The findings suggest public health policies should consider light pollution a modifiable risk factor for heart disease. Protecting circadian rhythms may be a powerful, yet underutilized, strategy in cardiovascular prevention—a call to view our modern lighting environments as a major health influence. Reference:Windred, D. P., et al. (2025). Light Exposure at Night and Cardiovascular Disease Incidence. JAMA Network Open. doi.org/10.1001/jamanetworkopen.2025.39031