The quality of your sleep goes beyond how long you rest.
New research indicates that sleeping in total darkness may play a crucial role in protecting your cardiovascular system.
Even low levels of ambient light during sleep can trigger stress-related brain activity that causes arterial inflammation.
This inflammation is a key contributor to heart attacks and strokes, demonstrating that light exposure at night is more than a minor nuisance it can be a serious health risk.
A recent study presented at the American Heart Association Scientific Sessions in 2025 examined 466 adults over a decade to investigate the effects of artificial light at night, or LAN, on heart health.
Participants with higher levels of nighttime light exposure were significantly more likely to develop major cardiovascular issues.
For each standard deviation increase in light exposure, the likelihood of a heart attack rose by 35 percent over five years and 22 percent over ten years.
These risks were even higher for individuals living in areas with elevated environmental stressors, such as traffic noise or lower neighborhood income.
The study used advanced PET/CT brain imaging and satellite-based measurements to track both brain activity and ambient light exposure in participants’ homes.
The findings add to a growing body of evidence highlighting the negative effects of nighttime light on neurophysiological systems, metabolism, and inflammation.
Experimental research supports these observational findings.
In a 2022 study, participants who slept in typical bedroom light around 100 lux experienced higher heart rates, less deep sleep, and impaired insulin sensitivity compared to those in dimmer environments under 3 lux.
These physiological changes demonstrate how even modest amounts of light can disrupt critical restorative processes during sleep.
Jonathan Cedernaes, PhD, a sleep expert at Uppsala Universitet in Sweden, notes that both animal and human studies consistently show that LAN interferes with multiple bodily systems.
Metabolic regulation and cardiovascular function are particularly vulnerable to disruption by light at night.
For practical steps, experts recommend creating a bedroom environment that blocks as much light as possible.
Blackout curtains, light-blocking sleep masks, and turning off electronic devices can help minimize LAN exposure.
Even small adjustments, like dimming or eliminating nightlights, can support deeper sleep and reduce inflammation.
The emerging consensus is clear: complete darkness while sleeping is not just a comfort preference it is a protective measure for your heart.
Prioritizing this simple yet powerful change may reduce your risk of arterial damage and long-term cardiovascular disease.
By combining consistent sleep schedules with a fully darkened room, you give your body the environment it needs to repair, regulate, and maintain heart health.
Good sleep is not optional. It is an essential component of a long, healthy life.