A new CVD risk factor emerges: Too much light exposure at night is bad for the heart
Too much light exposure at night, both when asleep and awake, may be bad for the heart. That was the eye-opening takeaway from a new study published in European Heart Journal.[1]
“Previous observational studies have linked nighttime light exposure with a higher risk of cardiovascular disease, but little is known about the related cardiac structure and functional changes,” senior author Lu Qi, MD, PhD, a researcher with Tulane University, said in a statement. “We carried out this research to find out what happens to the heart over time when people are exposed to too much light at nighttime.”
Qi et al. tracked data from more than 11,000 UK Biobank participants. They wore a light sensor on their wrists for seven days. Three years later, they all underwent a cardiac MRI scan.
Overall, study participants exposed to the most light—three lux or more—were associated with thickening of the wall of the left ventricle not seen in participants exposed to lower amounts of light. MRI results also showed that participants exposed to high amounts of light were experiencing issues with their heart muscle’s ability to flex during heartbeats, an early sign of heart damage.
“Light pollution has emerged as a new risk factor for cardiovascular disease,” Qi said. “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.”
Thomas Münzel, MD, a professor with University Medical Center Mainz in Germany, and two colleagues wrote an editorial in European Heart Journal exploring the implications of this study.[2]
“It is time for clinicians, particularly those managing patients with heart failure or atrial fibrillation, to start asking about the sleep environment: how dark the bedroom is, whether the patient works night shifts, and how much screen use occurs after sunset,” the group wrote. “The advice is simple and inexpensive: blackout curtains, warm-colored bedside lighting, and covering the small standby LEDs on household electronics.”
Münzel and colleagues emphasized that these findings are “more than an interesting observation.”
“It provides a crucial link between what satellites already show us, i.e. a planet glowing ever brighter at night, and the clinical reality unfolding inside our chests: hearts that are becoming stiffer, weaker, and less efficient,” they wrote. “The relationship is biologically coherent, the effect sizes are clinically meaningful, and the dose–response is unambiguous: more light, worse outcomes. The takeaway is clear, darkness deserves recognition as a vital sign, as essential to cardiovascular health as blood pressure control and clean air.”
Click here for the full analysis. Click here for the editorial.
Michael has more than 19 years of experience as a professional writer and editor. He has written at length about cardiology, radiology, artificial intelligence and other key healthcare topics.