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. 2025 Oct 1;8(10):e2539031.
doi: 10.1001/jamanetworkopen.2025.39031.

Light Exposure at Night and Cardiovascular Disease Incidence

Daniel P Windred  1 , Angus C Burns  2   3   4   5 , Martin K Rutter  6   7 , Jacqueline M Lane  2   3   4   5 , Richa Saxena  2   3   4   8 , Frank A J L Scheer  2   3   4 , Sean W Cain  1 , Andrew J K Phillips  1
Affiliations

Light Exposure at Night and Cardiovascular Disease Incidence

Daniel P Windred et al. JAMA Netw Open. .

Abstract

Importance: Light at night causes circadian disruption, which is a known risk factor for adverse cardiovascular outcomes. However, it is not well understood of cardiovascular diseases.

Objective: To assess whether day and night light exposure is associated with incidence of cardiovascular diseases, and whether associations of light with cardiovascular diseases differ according to genetic susceptibility, sex, and age.

Design, setting, and participants: This prospective cohort study analyzed cardiovascular disease records across 9.5 years (June 2013 to November 2022) from UK Biobank participants who wore light sensors in a naturalistic setting. Data were analyzed from September 2024 to July 2025.

Exposure: Approximately 13 million hours of light exposure data, tracked by wrist-worn light sensors (1 week each), categorized into the 0 to 50th, 51st to 70th, 71st to 90th, and 91st to 100th percentiles.

Main outcomes and measures: Incidence of coronary artery disease, myocardial infarction, heart failure, atrial fibrillation, and stroke after light tracking were derived from UK National Health Service records. Risks of cardiovascular diseases were assessed using Cox proportional hazards models (3 primary models adjusted at 3 levels) and reported as hazard ratios (HRs).

Results: A total of 88 905 individuals were included (mean [SD] age, 62.4 [7.8] years; 50 577 female [56.9%]). Compared with individuals with dark nights (0-50th percentiles), those with the brightest nights (91st-100th percentiles) had significantly higher risks of developing coronary artery disease (adjusted HR [aHR], 1.32; 95% CI, 1.18-1.46), myocardial infarction (aHR, 1.47; 95% CI, 1.26-1.71), heart failure (aHR, 1.56; 95% CI, 1.34-1.81), atrial fibrillation (aHR, 1.32; 95% CI, 1.18-1.46), and stroke (aHR, 1.28; 95% CI, 1.06-1.55). These associations were robust after adjusting for established cardiovascular risk factors, including physical activity, smoking, alcohol, diet, sleep duration, socioeconomic status, and polygenic risk. Larger-magnitude associations of night light with risks of heart failure (P for interaction = .006) and coronary artery disease (P for interaction = .02) were observed for females, and larger-magnitude associations of night light with risks of heart failure (P for interaction = .04) and atrial fibrillation (P for interaction = .02) were observed for younger individuals in this cohort.

Conclusions and relevance: In this cohort study, night light exposure was a significant risk factor for developing cardiovascular diseases among adults older than 40 years. These findings suggest that, in addition to current preventive measures, avoiding light at night may be a useful strategy for reducing risks of cardiovascular diseases.

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Conflict of interest statement

Conflict of Interest Disclosures: Dr Rutter reported receiving personal fees from Eli Lilly (consultancy) and having stock ownership in GSK outside the submitted work. Dr Scheer reported having served on the Board of Directors for the Sleep Research Society and receiving consulting fees from the University of Alabama at Birmingham, Morehouse School of Medicine, and Salk Institute for Biological Studies outside the submitted work. Dr Scheer’s interests were reviewed and managed by Brigham and Women’s Hospital and Mass General Brigham in accordance with their conflict of interest policies. Dr Cain reported being a cofounder of Circadian Health Innovations; having a pending patent without royalties (WO2021102504A1); receiving research funding from Versalux and Delos; having consulted for Dyson, Colorbeam, and Beacon Lighting; and having received a philanthropic donation from Beacon Lighting outside the submitted work. Dr Phillips reported receiving grants from Beacon, Versalux, and being a cofounder of Circadian Health Innovations outside the submitted work. No other disclosures were reported.

Figures

Figure 1.
Figure 1.. Participant Flow Diagram
This figure details participant-level exclusions between data collection and final analyses for each of the 5 incident cardiovascular outcomes. aCategories are not mutually exclusive.
Figure 2.
Figure 2.. Risk of Cardiovascular Diseases Within Day and Night Light Exposure Percentile Groups
Hazard ratios (HRs) and 95% CIs are adjusted for age, sex, race and ethnicity, and photoperiod (model 1); additionally adjusted for education, employment, income, and deprivation (model 2); and further adjusted for physical activity, smoking status, alcohol consumption, diet, and urbanicity (model 3). Participants with the darkest environments (0-50th percentiles) were the referent group for all models. HRs (95% CIs) are presented numerically in Table 2.
See this image and copyright information in PMC

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