When the night glows too bright, the heart may whisper warnings we cannot hear.
Bright Nights, Hidden Risks
Higher exposure to light during the late-night hours, specifically between 12:30 a.m. and 6 a.m., has been linked to an increased risk of cardiovascular problems, according to a study published in the Oct. 1, 2025, issue of JAMA Network Open. The research analysed the habits and health outcomes of nearly 89,000 adults aged 41 and older.
Participants wore light sensors on their wrists for a full week, allowing researchers to quantify their exposure to artificial light at night. Over an average follow-up period of 9.5 years, the study tracked the development of various heart-related conditions, including coronary artery disease, stroke, atrial fibrillation, heart attack, and heart failure. Notably, individuals with the highest levels of night-time light exposure showed a higher risk for these cardiovascular events compared with those who experienced less night-time illumination.
Why Darkness Matters
The researchers accounted for multiple other factors that could influence heart health, including traditional risks like smoking, high blood pressure, and cholesterol levels, as well as sleep-related variables such as duration and timing of sleep. Despite these adjustments, the associations between night-time light exposure and cardiovascular problems remained significant.
While the precise mechanisms behind these findings are not fully understood, scientists suggest that exposure to light during the night may disrupt both sleep quality and the body’s natural circadian rhythm. These disruptions, in turn, could contribute to an increased risk of heart disease and related conditions over time. The study highlights the importance of preserving dark, uninterrupted night hours as a potentially simple yet effective way to support long-term heart health.
Sometimes, it is in the quiet darkness that the heart truly finds its rhythm.
Summary
A study in JAMA Network Open found that people exposed to higher levels of light between 12:30 a.m. and 6 a.m. face increased risks of coronary artery disease, stroke, atrial fibrillation, heart attack, and heart failure. The research tracked nearly 89,000 adults for 9.5 years, suggesting that night-time light may disrupt sleep and circadian rhythms, affecting cardiovascular health.
