A Wake-Up Moment
It was just past midnight when I noticed the subtle glow of the router light under the TV stand. Outside, a pale orange wash from the streetlamp filtered through the curtains. I reached for my phone to check the time, and that soft blue light illuminated the entire room for a brief second.
That was when I started paying attention.
Across the world, researchers are uncovering the cumulative toll of light pollution inside our homes—especially in the bedroom. New data suggests that even moderate exposure to artificial light at night could be changing how our brains and bodies respond to stress, and not for the better.
What the Science Reveals
At Massachusetts General Hospital, a team led by Dr Shady Abohashem studied data from 466 adults who had previously undergone PET/CT scans. The scans revealed patterns of neural stress and arterial inflammation, offering a window into how our environment affects long-term health. When researchers cross-referenced residential light exposure with health outcomes, they found that individuals exposed to higher levels of artificial light during sleep had significantly more stress activity in the brain. This was accompanied by inflammation of the blood vessels, these being well-known precursors to cardiovascular disease. By the end of 2018, 17% of cohort subjects had undergone severe heart-related incidents.
Presented at the 2025 American Heart Association Scientific Sessions, the findings held even when external stressors such as traffic noise and lower neighbourhood income were accounted for. The link between nighttime brightness and cardiovascular risk remained clear.
Previous studies also supported those ideas. Northwestern University scientists in 2022 observed that sleeping under a room light of just 100 lux—a dim light scenario—raised heart rate and decreased insulin sensitivity in healthy adults the next day. That study also emphasised how one night of exposure would disrupt natural glucose metabolism in the body, thus compromising energy regulation. Bodies react to light by suppressing melatonin production, thus influencing circadian rhythm and autonomic nervous function. Slowly but surely, these alterations would initiate the factors for heart diseases, obesity, and type 2 diabetes.
A Global Public Health Concern
This isn’t a localised issue. Cities from São Paulo to Seoul are witnessing a rise in ambient light levels that seep into residential areas. In a global context, the satellite-based 2016 New World Atlas of Artificial Night Sky Brightness indicated that over 80% of the world’s population now lives under light-polluted skies. In Europe and North America, that figure climbs to over 99%.
In another large-scale analysis, a cohort study involving more than 88,000 adults showed a correlation between higher residential light exposure and increased risks of atrial fibrillation, heart failure, stroke, and coronary artery disease. The breadth of the sample added weight to the hypothesis that the problem isn’t isolated to individual behaviours but is woven into the urban fabric itself.
What You Can Actually Do
Abstractly said, awareness is at the forefront of any change. Knowing that exposure to artificial lights during the state of sleep poses a definite health risk can take whatever form towards helping people approach their nightly regimes. Simple interventions requiring minimal effort, such as installing blackout curtains or removing standby lights from the bedroom, might relieve some brain activities related to stress. Dimming the lights in the hours before sleep and charging devices outside the room are other actions recommended by the above results.
None of these requires overhauling your lifestyle. You don’t need specialised equipment. Just pay attention to your environment.
A Market Opportunity for Brands
The conversation doesn’t end with individuals. Companies operating in the health tech, wellness, or home appliance sectors have a role to play. Philips, for example, has released lighting systems with circadian rhythm settings. Sleepwear and home goods brands are positioning blackout-friendly products as essential to rest, not luxury. These aren’t marketing gimmicks. They respond to a growing body of research and a rising public interest in sleep health.
Urban planning is also evolving. Some cities are experimenting with street lighting strategies that reduce skyglow, adjusting the intensity and wavelength of public lighting to mitigate biological effects. These changes won’t happen overnight. But they mark a shift in how we think about light—not just as a tool, but as an environmental factor that impacts our health.
Simple Questions, Real Impact
The data points to one consistent recommendation: sleeping in total darkness may reduce brain stress, inflammation, and heart risk. That means identifying and minimising every source of artificial light in the room.
Can you see your hand in front of your face after lights out? Is there a blinking router light in your room? Are screens a part of your bedtime routine?
None of these questions requires medical training. But the answers might help you sleep better—and stay healthier.
Science doesn’t claim sleeping in darkness will fix everything. But study after study continues to link light exposure at night with elevated risk factors. This is an actionable area of personal health—one entirely within your control.
Rethinking Light
As more evidence emerges, global brands that adapt to these insights will lead with both relevance and responsibility. And for consumers, the path is straightforward: rethink how your bedroom is lit and whether that quiet glow might be doing more harm than good.