Could nighttime light be quietly changing the heart?

Clinical takeaway: Consider asking patients with or at risk for heart failure or atrial fibrillation about nighttime light and their sleep environment. Although causality remains unproven, using blackout curtains, choosing dim warm-colored lighting, limiting screen use, and covering indicator lights are low-risk steps that may support sleep and cardiovascular health.

Artificial light at night has been associated with cardiovascular disease, but its effects on the heart itself have been unclear. A UK Biobank study now links greater nighttime light exposure to subtle structural and functional changes across several heart chambers.

Researchers studied 11,071 adults without cardiovascular disease who wore wrist light sensors for seven days and underwent cardiac MRI about three years later. Compared with participants who had essentially no exposure to light at night, those with high exposure had 2.4% greater left ventricular mass relative to body size, 1.5% greater mean wall thickness, and a 1.9% lower myocardial contraction fraction. Measures of myocardial strain were also approximately 3% worse.

Similar structural and functional changes were seen in the right ventricle and left atrium, with cardiac findings becoming progressively less favorable as nighttime light exposure increased.

Researchers also examined longer-term clinical outcomes in a separate analysis of more than 70,000 participants followed for about 8 to 10 years. High nighttime light exposure was associated with higher risks of heart failure (29%), atrial fibrillation (15%), myocardial infarction (24%), stroke (33%), and cardiovascular death (26%).

Shorter sleep duration statistically explained 24% to 49% of many associations, suggesting that sleep disruption may be one—but not the only—pathway. By linking nighttime light to both early cardiac changes and later cardiovascular events, the study provides a rationale for clinicians to consider sleep environment as part of cardiovascular risk counseling.

“Light pollution has emerged as a new risk factor for cardiovascular disease. Our findings, together with evidence from other studies, suggest that reduction of nighttime light exposure should be considered as one of the potential strategies for preventing heart disease by clinicians and policy makers,” said study author Lu Qi, MD, PhD, professor at Tulane University.

Source: Dai J, et al. (2026 Sep 9) Eur Heart J. Nighttime light exposure and cardiac structure and function