Common bedroom mistake could be quietly taking a toll on your health, experts say
Nighttime Light Exposure May Heighten Risk of Heart Disease, Tulane Study Finds
A new research effort from Tulane University has revealed that even modest amounts of light at night—levels comparable to a full‑moon glow—can increase the likelihood of serious cardiovascular events. The study, which examined data from thousands of participants over several years, found that those exposed to more than 3 lux of illumination while sleeping were at higher risk for heart failure, atrial fibrillation, heart attack, stroke, and heart‑related death.
The findings come as a reminder that the body’s internal clock, or circadian rhythm, is tightly linked to light. “The circadian rhythm is strongly influenced by light entering the eyes – light exposure signals the brain to suppress melatonin production, a hormone that helps regulate the timing of sleep, while low light levels signal the brain to produce more melatonin,” explained Chelsie Rohrscheib, Ph.D., a sleep expert and neuroscientist based in Michigan. “As melatonin levels rise in the evening, they help prepare the brain and body for sleep. Light pollution from various sources in our bedroom can trick the brain into producing less melatonin, which can negatively impact sleep quality.”
Rohrscheib added that chronic, consistent exposure to light at night can erode overall sleep quality, which in turn impairs vital physiological processes. “Sleep plays an essential role in many biological processes, including body and brain restoration, hormone release, immune system functioning, cognitive processes such as memory consolidation, brain waste clearance and metabolic regulation,” she said. “When sleep is consistently poor, these processes do not function optimally, which in turn elevates the risk for many chronic health conditions such as hypertension, cardiovascular disease, stroke, type 2 diabetes, obesity, neurodegenerative diseases, certain cancers and mood disorders.”
A separate study from Northwestern Medicine that Rohrscheib cited showed that a single night of sleeping with moderate light exposure (about 100 lux) can disrupt glucose regulation, elevate heart rate, and reduce heart‑rate variability—an early marker of sympathetic nervous system activity. “Consistent light exposure will chronically reduce overall sleep quality,” she warned.
Sleep researcher Ashley Curtis, Ph.D., an assistant professor at the University of South Florida College of Nursing, echoed concerns about the long‑term health consequences. “Emerging evidence even suggests that it affects the gut microbiome, everything from digestion to immunity,” she told reporters. “Sleep impairment is also linked to increased risk of mortality.” She highlighted that certain groups—shift workers, children, older adults, and individuals with insomnia or mood disorders—might be especially vulnerable. “Blue wavelength light from TVs and phones is the most disruptive because people’s retinas are most sensitive to it,” she said. “Dim, warm, red‑toned night lights cause far less circadian impact – these are natural sunset colors one would see in the evenings.”
Curtis also noted age‑related differences. “Older adults often become less sensitive to light, meaning bright or short‑wavelength light has a weaker effect on suppressing melatonin than it does in younger adults,” she explained. “The caveat, however, is that older adults also experience a higher baseline prevalence of sleep disruption, which can bidirectionally impact the circadian system.” She emphasized that even dim light can initially suppress melatonin, but the body can recover if the exposure is brief. “Research shows that even if dim light impacts melatonin initially, it allows time for the body to recover,” Curtis said. “Therefore, it doesn’t disrupt your sleep to the degree that brighter light does.”
Dr. Alex Dimitriu, a double‑board‑certified sleep‑medicine physician and founder of Menlo Park Psychiatry & Sleep Medicine, agreed on the importance of lighting choices. “Shift workers, children, older adults, and individuals with insomnia or mood disorders are especially vulnerable to the effects of light on sleep depth,” he said. “Dim, warm, red‑toned night lights cause far less circadian impact.” He added that blackout curtains remain the gold standard for those seeking optimal sleep, but “you don’t need to have absolute darkness to maintain a healthy sleep environment.”
The Tulane study underscores that the simple act of leaving a nightlight on or using a phone for a few minutes before bed can have measurable effects on heart health over time. While the research does not yet establish a direct causal pathway, it reinforces the growing consensus among sleep scientists that maintaining a dark, cool bedroom is one of the most effective strategies for protecting cardiovascular health.
For readers looking to reduce nighttime light exposure, experts suggest turning off bright screens at least an hour before sleep, using dim, warm‑colored bulbs for any necessary illumination, and considering blackout curtains or eye masks if light leaks into the bedroom. As the science of sleep continues to evolve, the message remains clear: the light we keep on after dark may be doing more harm than we realize, especially for our hearts.
