Even Low Levels of Light During Sleep Linked to Higher Risk of Heart Failure and Atrial Fibrillation
New research published in September 2026 found that exposure to even low levels of light, as little as 3 lux, during sleep is associated with increased risks of heart failure and atrial fibrillation. Researchers say the findings suggest that sleeping in a dark room may be an important and overlooked factor in cardiovascular health.
New research published in September 2026 found that exposure to even low levels of light during sleep is linked to a higher risk of heart failure and atrial fibrillation.
The study found that exposure to light as low as 3 lux during sleep, roughly equivalent to the glow of a nightlight or a streetlight filtering through curtains, was associated with measurable increases in cardiovascular risk. Atrial fibrillation, an irregular heart rhythm that raises the risk of stroke, and heart failure were both more common among people who slept in rooms with low-level light exposure.
Researchers said the findings point to a biological mechanism involving disruption of the body's circadian rhythm. Light exposure during sleep can suppress melatonin production and interfere with the body's natural overnight repair processes, which may affect heart function over time.
The study adds to a growing body of evidence linking sleep environment to long-term health outcomes. Previous research has connected light exposure during sleep to higher rates of obesity, diabetes, and depression.
Experts say the practical takeaway is straightforward: sleeping in a dark room matters. Blackout curtains, covering LED indicator lights on electronics, and avoiding screens before bed can all reduce light exposure during sleep.
The research was published in a peer-reviewed journal and involved a large sample of adults tracked over multiple years. Researchers called for further studies to determine whether reducing light exposure during sleep can directly lower cardiovascular risk.
