Tulane University Study Links Nighttime Light Exposure to Cardiovascular Disease Risk
Exposure to artificial light during sleep—even at levels as low as 3 lux, roughly the brightness of moonlight—is associated with a higher risk of cardiovascular disease, according to a new study from Tulane University. Researchers found that nighttime light exposure correlates with increased risks of heart failure, atrial fibrillation, heart attack, stroke, and cardiovascular death.
The findings build on broader research examining how ambient light at night impacts human health. A separate study involving 466 adults tracked via Massachusetts General Hospital scans found that higher levels of artificial light at night increased the likelihood of a heart attack by 35% over five years and 22% over a 10-year period.
How Circadian Rhythms and Melatonin Respond to Bedroom Lighting
Sleep is partially controlled by the circadian rhythm, which acts as the brain’s internal 24-hour clock regulating sleep and wakefulness, according to Chelsie Rohrscheib, Ph.D., a sleep expert and neuroscientist based in Michigan. Light entering the eyes signals the brain to suppress melatonin production, a hormone that manages the timing of sleep.
“As melatonin levels rise in the evening, they help prepare the brain and body for sleep,” Rohrscheib told Fox News Digital. “Light pollution from various sources in our bedroom can trick the brain into producing less melatonin, which can negatively impact sleep quality.”
Consistent light exposure chronically reduces overall sleep quality, interrupting biological processes such as hormone release, immune system function, and metabolic regulation. Rohrscheib noted that a 2022 Northwestern Medicine study demonstrated how just one night of sleeping with moderate light exposure at 100 lux disrupted glucose regulation while increasing heart rate and sympathetic nervous system activity.
Vulnerable Populations and the Impact of Blue Wavelengths
Certain groups face heightened sensitivity to nighttime light exposure. Alex Dimitriu, M.D., a double board-certified sleep medicine doctor and founder of Menlo Park Psychiatry & Sleep Medicine, told Fox News Digital that shift workers, children, older adults, and individuals with insomnia or mood disorders are especially vulnerable to the disruption of sleep depth.
Different types of light carry varying levels of disruption. Dimitriu explained that blue wavelength light from televisions and mobile phones is the most disruptive because human retinas are most sensitive to it, leading to maximal melatonin suppression. Conversely, dim, warm, red-toned night lights cause far less circadian impact, mirroring natural sunset colors.
Ashley Curtis, PhD, a sleep researcher and assistant professor at the University of South Florida College of Nursing, agreed that warmer, dimmer light with longer wavelengths does not impact melatonin production to the same severe degree as brighter light, allowing the body time to recover.
Pro Tip: Cultivating a Healthy Sleep Environment
Experts recommend several practical changes to optimize your bedroom without requiring pitch-black conditions:
- Turn off harsh overhead lights one to two hours before bed.
- Place night lights close to the floor.
- Use bulbs that are dimmer and emit warmer light, such as orange, amber, or red.
- Discontinue screen use at least one hour before bedtime.
- Layer window treatments to soften bright street lighting, or consider a face mask.
Frequently Asked Questions
How much light exposure during sleep is considered harmful?
Research from Tulane University links exposure to more than 3 lux of light—roughly equivalent to moonlight—to increased cardiovascular risks, including heart attack, stroke, and heart failure.
Why is blue light more disruptive to sleep than other colors?
According to Alex Dimitriu, M.D., human retinas are most sensitive to blue wavelength light from screens like phones and TVs, which maximally suppresses the production of the sleep hormone melatonin.
Do older adults react to nighttime light the same way younger adults do?
Ashley Curtis, PhD, notes that older adults often become less sensitive to light, meaning short-wavelength light has a weaker direct effect on suppressing melatonin compared to younger demographics, though older populations already experience a higher baseline prevalence of sleep disruption.
To learn more about maintaining healthy sleep habits and protecting your long-term cardiovascular health, explore our related health resources or subscribe to our newsletter for weekly updates.
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