Study Links Nighttime Light Exposure to Increased Cardiovascular Risks

Researchers from the Flinders Health and Medical Research Institute in Australia, collaborating with colleagues in the United Kingdom and the United States, have uncovered significant associations between increased nighttime light exposure and heightened risks of various cardiovascular diseases. The study, titled "Personal night light exposure predicts incidence of cardiovascular diseases in >88,000 individuals," was published on medRxiv on June 20, 2025, and represents a substantial advancement in understanding how circadian rhythms influence heart health.

The study analyzed data from 88,905 participants in the UK Biobank, with a mean age of 62.4 years and a demographic distribution of 56.9% female. Participants wore wrist-based light sensors for one week between 2013 and 2016 across England, Scotland, and Wales. Researchers employed hazard modeling to examine the relationship between both day and night light exposure and new diagnoses of five major cardiovascular conditions: coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke. Data from the National Health Service (NHS) was utilized to track diagnoses up until November 2022.

The findings revealed a concerning correlation; individuals exposed to brighter nights were at a significantly higher risk for all five cardiovascular outcomes. Specifically, those in the 90–100th percentile of nighttime light exposure faced a 23-32% increased hazard for coronary artery disease, a 42-47% increase for myocardial infarction, a 45-56% rise for heart failure, a 28-32% increase for atrial fibrillation, and a 28-30% increase for stroke compared to those in the lowest exposure percentile (0-50th).

Dr. Daniel P. Windred, a leading researcher on the project, stated, "Our study underscores the critical importance of circadian rhythms in cardiovascular health. The disruptions caused by artificial light at night may lead to significant metabolic and vascular changes that increase cardiovascular risks."

These associations were found to persist even after controlling for various factors including physical activity, smoking, alcohol consumption, dietary habits, and socio-economic status. Notably, the researchers identified that women exhibited stronger correlations for heart failure and coronary artery disease, while younger participants showed heightened associations for heart failure and atrial fibrillation.

Circadian rhythms play a vital role in regulating physiological processes such as blood pressure, heart rate, and glucose metabolism. Long-term disruptions to these rhythms, as highlighted by the study, have been linked to adverse health outcomes including myocardial fibrosis, hypertension, and inflammation.

Experts have long posited that artificial nighttime light exposure can interfere with physiological processes, leading to increased cardiovascular risks. According to Dr. Sarah Johnson, Professor of Public Health at the University of California, Los Angeles, and co-author of a related 2024 study published in the Journal of Epidemiology, "The accumulated evidence suggests that minimizing exposure to artificial light during nighttime could be a straightforward yet effective strategy for cardiovascular disease prevention."

The implications of this research extend beyond individual health. Urban planners and policymakers are encouraged to consider circadian health in their designs and regulations. The authors of the study advocate for the adoption of circadian-informed lighting guidelines in homes, workplaces, hospitals, and public spaces to mitigate the adverse effects of artificial light exposure.

As the study progresses through peer review and potential publication in a reputable journal, it is anticipated that further investigations will explore practical applications of these findings. Future research may also delve into the biological mechanisms linking circadian disruption to cardiovascular pathology.

In conclusion, this groundbreaking study highlights the urgent need for awareness regarding the impact of nighttime light exposure on cardiovascular health, suggesting that strategies to minimize such exposure could play a crucial role in public health initiatives aimed at reducing cardiovascular disease prevalence. The call for circadian-informed lighting practices represents a pivotal step toward safeguarding population health in an increasingly illuminated world.