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Streetlights and traffic light pollution disrupt natural sleep cycles and can cause insomnia. They also appear to increase stroke risk. Poor nighttime rest puts strain on the heart and other organs.
Researchers at several major Chinese centers enrolled 28,300 volunteers from Ningbo, a port city. The participants’ average age was 62. None had a history of cerebrovascular diseases — the noncommunicable conditions caused by damage to the brain’s blood vessels, including stroke.
They followed participants for six years, tracking new cases of cerebrovascular disease. Over that time the team recorded 1,278 cases, 900 of which were strokes.
To estimate each participant’s nighttime light exposure, the researchers used satellite imagery. They adjusted the results for age, gender, and income, according to the Daily Mail.
What the study found
Many people leave their blinds up at night, following a wellness trend that encourages waking with the sun.
Dr. Jian-Bing Wang, a co-author of the study, said, “High levels of exposure to external artificial light at night may be a risk factor for cerebrovascular diseases.”
The team advised people—especially city dwellers—on how best to protect themselves from this exposure.
They warned that bright light at night can suppress melatonin secretion and disrupt the body’s circadian rhythms. That disruption can lead to higher blood pressure and blood glucose levels, which are triggers for cardiovascular disease.
The researchers said about 80 percent of the world’s population live in areas with bright nighttime lighting, which can make it harder to fall and stay asleep.
The findings were published in the journal Stroke.
Previous research recommends 7 to 9 hours of sleep each night.
