Sleeping with a nightlight may feel routine, but new research is raising concerns about what nighttime illumination could mean for cardiovascular health. A Tulane University study linked light exposure during sleep with a higher risk of cardiovascular disease.

Researchers found that exposure to more than 3 lux of light, roughly the brightness of moonlight, was associated with increased risks of heart failure, atrial fibrillation, heart attack, stroke and cardiovascular death. Atrial fibrillation is an irregular and often very rapid heart rhythm.

Household surroundings and ambient neighborhood conditions can directly interfere with restful sleep, according to Erin Palinski-Wade, a New Jersey nutritionist and author of “The Sleepdemic Solution.” Light entering the bedroom from either indoor or outdoor sources may affect the body’s sleep processes.

Sleep is partially controlled by the circadian rhythm, the brain’s internal 24 hour clock that regulates sleep and wakefulness, according to Chelsie Rohrscheib, Ph.D., a sleep expert and neuroscientist based in Michigan. That rhythm is strongly influenced by light entering the eyes.

Light exposure signals the brain to suppress production of melatonin, a hormone that helps regulate sleep timing. Lower light levels signal the brain to produce more melatonin, helping prepare the brain and body for sleep as evening arrives.

Light pollution from various sources in the bedroom can trick the brain into producing less melatonin, Rohrscheib told Fox News Digital. Consistent exposure can chronically reduce overall sleep quality, potentially interfering with processes that depend on adequate rest.

Sleep plays an essential role in body and brain restoration, hormone release, immune system function and cognitive processes such as memory consolidation. It also supports brain waste clearance and metabolic regulation, making persistent sleep disruption a concern that extends beyond feeling tired.

When sleep is consistently poor, those processes do not function optimally, Rohrscheib warned. Poor sleep can elevate the risk of chronic health conditions including hypertension, cardiovascular disease, stroke, type 2 diabetes, obesity, neurodegenerative diseases, certain cancers and mood disorders.

Rohrscheib also cited a 2022 Northwestern Medicine study that examined a single night of sleep with moderate light exposure measured at 100 lux. The study found disrupted glucose regulation, increased heart rate and greater sympathetic nervous system activity, reflected by reduced heart rate variability.

Sleep impairment is also linked to an increased risk of mortality, according to Ashley Curtis, PhD, a sleep researcher and assistant professor at the University of South Florida College of Nursing. Emerging evidence suggests that disrupted sleep also affects the gut microbiome, including digestion and immunity.

Some people may be particularly sensitive to nighttime light. Alex Dimitriu, M.D., a double board-certified sleep medicine doctor and founder of Menlo Park Psychiatry & Sleep Medicine, identified shift workers, children, older adults and people with insomnia or mood disorders as especially vulnerable.

Curtis noted that older adults often become less sensitive to light, so bright or short wavelength light may have a weaker effect on melatonin suppression than it does among younger adults. However, older adults also have a higher baseline prevalence of sleep disruption, which can affect the circadian system in both directions.

There is also some evidence that bright light has a more pronounced impact on melatonin suppression in men, Curtis noted. For people with insomnia, bright light exposure before bedtime can worsen existing sleep disruption by further interfering with the biological circadian rhythm.

Blue wavelength light from televisions and phones is the most disruptive because the retina is particularly sensitive to it, according to Dimitriu. This type of light maximally suppresses melatonin, while dim, warm and red toned nightlights have far less circadian impact.

Curtis similarly noted that warmer and dimmer light with a longer wavelength does not affect melatonin production as strongly. Even when dim light initially affects melatonin, research indicates that it gives the body time to recover and does not disrupt sleep as much as brighter light.

The experts recommend turning off harsh overhead lights one to two hours before bed. They also advise using dimmer bulbs that produce warmer light with longer wavelengths, such as orange, amber or red.

Screen use involving computers and phones should stop at least one hour before bedtime to eliminate brain stimulation. Layered window treatments can soften bright street lighting, while a face mask may further prevent light pollution from affecting sleep quality.