Exposure to light at night may be linked to potentially harmful changes in heart’s structure and performance, according to study involving more than 11,000 people. Findings were published in European Heart Journal.
Research was led by Professor Lu Qi of Tulane University, New Orleans, USA. He said: “Previous observational studies have linked nighttime light exposure with higher risk of cardiovascular disease, but little is known about related cardiac structure and functional changes. We carried out this research to find out what happens to heart over time when people are exposed to too much light at nighttime.” This is first study of its kind to link measured night light to detailed cardiac MRI remodeling.
Measuring Nighttime Light Exposure With Wrist Sensor For 7 Days
Study included 11,071 participants from UK Biobank. Each person wore light sensor on wrist for seven days so researchers could measure how much light they were exposed to at night in real life, not just self-reported bedroom brightness.
Three years later, participants underwent cardiac MRI scans. These detailed scans allowed researchers to examine both structure of heart and how effectively it was functioning over time.
Team compared people exposed to more than three lux of nighttime light with those exposed to almost no light at night. Lux is measure of how much visible light reaches surface. Three lux is dim, equivalent to faint hallway light, yet still associated with changes.
Changes In Multiple Heart Chambers – Left Ventricle Thickening Found
People with higher nighttime light exposure showed thickening in wall of left ventricle, one of chambers of heart. That thickening reduced amount of space available inside chamber for blood. Researchers also found evidence heart muscle was less able to flex properly during each heartbeat. Reduced flexibility can be early sign heart is not functioning normally and moving toward stiffness. Changes were also observed in right ventricles and left atria, two other chambers of heart, suggesting association was not limited to single part of organ but widespread cardiac remodeling.
Professor Qi said: “This is first study of its kind, and it shows exposure to higher levels of light at nighttime is linked to cardiac remodeling. This is where structure and function of heart changes and we typically see it in response to chronic stress or injury to heart.”
“It’s our body’s way of adapting to that stress, but ultimately it weakens heart and can lead to heart failure. Light pollution has emerged as new risk factor for cardiovascular disease,” Qi explained.
“Our findings, together with evidence from other studies, suggest reduction of nighttime light exposure should be considered as one of potential strategies for preventing heart disease by clinicians and policy makers,” he added.
Analysis: Could Darker Bedroom Help Protect Heart?
In accompanying editorial, Professor Thomas Münzel from University Medical Center Mainz, Germany, and colleagues argued doctors should pay more attention to patients’ nighttime light environments. They said: “It is time for clinicians, particularly those managing patients with heart failure or atrial fibrillation, to start asking about sleep environment: how dark bedroom is, whether patient works night shifts, and how much screen use occurs after sunset.”
“The advice is simple and inexpensive: blackout curtains, warm-coloured bedside lighting, and covering small standby LEDs on household electronics. From public health perspective, implications are larger still. Light pollution is one of few environmental hazards that cities can control directly and affordably,” editorial noted.
“Shielded fixtures, warm-spectrum bulbs, and dimming or motion-activated streetlights are already available, energy-efficient, and climate-friendly,” authors added.
“Ultimately, this study is more than interesting observation. It provides crucial link between what satellites already show us, i.e., planet glowing ever brighter at night, and clinical reality unfolding inside our chests: hearts that are becoming stiffer, weaker, and less efficient.” “The relationship is biologically coherent, effect sizes are clinically meaningful, and dose-response is unambiguous: more light, worse outcomes. Takeaway is clear: darkness deserves recognition as vital sign, as essential to cardiovascular health as blood pressure control and clean air,” editorial concluded.
Q&A
Q: Does sleeping with light on damage your heart?
A: European Heart Journal study of 11,071 found >3 lux nighttime light linked to left ventricle thickening and reduced heart muscle flexibility after 3 years.
Q: How was nighttime light measured in heart study?
A: UK Biobank participants wore wrist light sensor for 7 days to measure real night exposure, followed by cardiac MRI 3 years later to assess remodeling.
Q: How to protect heart from light pollution at night?
A: Editorial advises blackout curtains, warm-coloured bedside lights, covering standby LEDs, less screen after sunset, and city-level shielded warm streetlights.
FAQ
1. Where was light at night heart study published?
Study published September 9 in European Heart Journal led by Professor Lu Qi Tulane University using 11,071 UK Biobank participants.
2. What heart changes were linked to night light exposure?
Thickening of left ventricle wall reducing chamber space, reduced flex during heartbeat, plus changes in right ventricle and left atria indicating cardiac remodeling.
3. What is 3 lux light exposure?
Lux measures visible light reaching surface; 3 lux is dim light, like faint night light or hallway glow, compared to near-dark <1 lux.
4. Is light pollution now considered heart disease risk factor?
Researchers say light pollution has emerged as new risk factor for cardiovascular disease alongside known factors; dose-response shows more light worse outcomes.
5. Should doctors ask about bedroom darkness?
Yes, editorial by Professor Thomas Münzel Mainz says clinicians managing heart failure or atrial fibrillation should ask about bedroom darkness, night shifts, screen use after sunset.
Disclaimer; This article is for informational purposes only and does not constitute medical advice. Always consult qualified healthcare professionals or cardiologists for heart failure, atrial fibrillation, or cardiovascular disease prevention.
