Flinders Health and Medical Research Institute researchers, in collaboration with colleagues from the UK and U.S., have uncovered a significant link between increased exposure to bright night-time light and a higher risk of developing five major cardiovascular diseases.
Our bodies operate on circadian rhythms, which regulate various functions such as blood pressure, heart rate, hormone secretion, and glucose metabolism. Disruption of these rhythms, as seen in animal and human studies, can lead to conditions like myocardial fibrosis, hypertension, inflammation, and imbalanced autonomic function. Previous research in this area has often relied on satellite data or small-scale studies using light sensors in bedrooms or on wrists, which didn’t capture individual exposure patterns on a larger scale.
In a recent study titled “Personal night light exposure predicts incidence of cardiovascular diseases in >88,000 individuals,” published on medRxiv, researchers analyzed data from 88,905 participants in the UK Biobank. These individuals, with an average age of 62.4 years and a majority of females, wore wrist-based light sensors for a week between 2013 and 2016 across England, Scotland, and Wales.
The study linked night and day light exposure levels with the occurrence of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke, as recorded in National Health Service files up to November 2022. The analysis adjusted for various factors such as age, sex, ethnicity, socioeconomic status, lifestyle habits, sleep patterns, clinical risk factors, and genetic predisposition.
Results showed a clear dose-response relationship between brighter night-time light exposure and a higher risk of all five cardiovascular outcomes. Participants in the 90-100th percentile of night-time light exposure had a significantly increased hazard for coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke compared to those in the 0-50th percentile.
Even after accounting for factors like physical activity, smoking, diet, and genetic risk, the association between bright night-time light and cardiovascular diseases remained strong. Interestingly, women exhibited a more pronounced risk for heart failure and coronary artery disease, while younger participants showed a higher risk for heart failure and atrial fibrillation.
The authors suggest that circadian misalignment caused by excessive artificial light at night may disrupt metabolic and vascular functions, leading to an elevated risk of cardiovascular diseases. This disruption could contribute to conditions like endothelial dysfunction, atherosclerosis, hypercoagulability, high blood pressure, and arrhythmias.
As a practical recommendation, the authors propose avoiding exposure to bright light during usual sleep hours as an additional preventive measure against cardiovascular diseases. They advocate for the implementation of circadian-informed lighting strategies in homes, hospitals, and urban planning to mitigate the adverse effects of artificial light on cardiovascular health.
This study sheds light on the importance of considering light exposure as a factor in cardiovascular health and emphasizes the need for tailored interventions to address the risks associated with disrupted circadian rhythms. The findings underscore the intricate relationship between our environment, daily habits, and overall well-being, highlighting the significance of maintaining a healthy balance in our exposure to light sources.
