Bright Nights, Weak Hearts: Study Links Nighttime Light Exposure to Higher Heart Disease Risk
USA: A new study published in JAMA Network Open has revealed that exposure to bright light during nighttime hours may increase the likelihood of developing cardiovascular diseases among adults over 40.
The research, conducted by Daniel P. Windred and colleagues from the Flinders Health and Medical Research Institute (Sleep Health) at Flinders University, Australia, emphasizes the potential cardiovascular hazards of nighttime light pollution.
The large-scale cohort study analyzed data from 88,905 participants of the UK Biobank who were followed for an average of 9.5 years. Participants aged 40 and above wore wrist sensors that continuously recorded their light exposure for one week in a natural environment. Over 13 million hours of light exposure were evaluated and categorized into four groups based on brightness levels during the night.
The study led to the following findings:
- Individuals exposed to the brightest nighttime light (91st–100th percentile) showed significantly higher risks of cardiovascular conditions compared with those experiencing darker nights (0–50th percentile).
- The adjusted hazard ratios (aHRs) were 1.32 for coronary artery disease, 1.47 for myocardial infarction, 1.56 for heart failure, 1.32 for atrial fibrillation, and 1.28 for stroke.
- These associations remained significant even after adjusting for major cardiovascular risk factors, including smoking, physical activity, alcohol use, diet, sleep duration, socioeconomic status, and genetic predisposition.
- The effects of nighttime light exposure were more pronounced in women and younger adults, indicating possible biological or behavioral factors contributing to increased vulnerability.
According to the researchers, light exposure at night may disrupt the circadian rhythm—the body’s internal clock that regulates sleep and other physiological processes—thereby contributing to adverse cardiovascular outcomes. This circadian misalignment has been linked in earlier studies to metabolic disturbances, hypertension, and inflammation, which collectively elevate cardiovascular risk.
“Cardiovascular disease remains the leading cause of global death and disability,” the authors noted. “In addition to traditional preventive measures such as a balanced diet, regular exercise, and avoiding alcohol and tobacco, limiting light exposure at night could serve as a novel preventive approach.”
While the study provides compelling evidence linking night light to cardiovascular health, the researchers acknowledged several limitations. The UK Biobank participants were predominantly White (97%) and generally healthier than the general population, which could limit the generalizability of the results. Moreover, light exposure was tracked for only one week, and information about specific light sources—such as digital screens or outdoor lighting—was unavailable.
Despite these constraints, the study marks a significant step in understanding environmental factors affecting cardiovascular health. The authors emphasized the need for long-term, circadian-informed interventions to clarify whether reducing nighttime light exposure can directly lower cardiovascular disease incidence.
The pioneering research identifies nighttime light exposure as a potentially modifiable environmental risk factor for heart disease. Reducing exposure to artificial light during the night, the authors suggest, could be a simple yet impactful addition to existing strategies for cardiovascular disease prevention.
Reference:
Windred DP, Burns AC, Rutter MK, et al. Light Exposure at Night and Cardiovascular Disease Incidence. JAMA Netw Open. 2025;8(10):e2539031. doi:10.1001/jamanetworkopen.2025.39031
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