A bedroom lamp, streetlight coming through the window or the glow from electronic devices may seem harmless at bedtime. But new research suggests that regular exposure to light during the night could have implications beyond sleep, potentially affecting cardiovascular health.
A study published in the European Heart Journal examined more than 11,000 people and found that greater nighttime light exposure was associated with changes in heart structure and function.
The Heart May Respond to Nighttime Light
Researchers found that people exposed to higher levels of light at night showed signs of changes in several chambers of the heart, including increased heart muscle mass and alterations in cardiac function.
These findings add another dimension to the growing research around light exposure and health.
Sleep Could Be Part of the Explanation
Nighttime light can interfere with the body’s natural circadian rhythm and may reduce sleep duration. In the new study, shorter sleep statistically explained part of the relationship between nighttime light exposure and changes in the heart.
This suggests that maintaining a healthy sleep environment could be relevant to cardiovascular wellbeing.
Heart Risks Were Also Observed
During follow-up, participants with higher nighttime light exposure had higher observed risks of heart failure, atrial fibrillation, heart attack, stroke and cardiovascular death compared with those reporting no nighttime exposure.
However, these are observational associations, so the research does not establish that bedroom light directly causes these conditions.
What Counts as Nighttime Light?
Nighttime exposure can come from several sources: outdoor street lighting, bedside lamps, television screens, electronic devices and other illumination around the bedroom.
Even relatively low levels of light may matter, with the study examining exposure above 3 lux.
Creating a Darker Sleep Environment
Making the bedroom darker is a simple habit that may support better sleep. People can consider using blackout curtains, switching off unnecessary lights and keeping bright screens away from the sleeping area.
These measures should be viewed as part of healthy sleep habits rather than a substitute for medical treatment.
Don’t Panic About a Little Light
The findings should not be interpreted as proof that every person sleeping with a night-light is going to develop heart disease. The study examined population-level associations and has limitations, including the UK Biobank’s predominantly White and relatively healthy population.
A Simple Sleep Habit Worth Considering
The research adds to evidence suggesting that dark nights and adequate sleep may be important components of cardiovascular health.
For people who can comfortably reduce unnecessary light around bedtime, creating a darker bedroom may be a simple addition to an overall healthy sleep routine.