Sleeping with the curtains open can increase the risk of stroke by up to 43 percent, a study suggests.
Street lights and light pollution from traffic disrupt the body’s natural sleep-wake cycle and not getting enough quality rest puts a strain on the heart and other organs.
Researchers in China made the discovery after comparing data from thousands of people.
Scientists suggested the bright lights disrupted people’s natural sleep-wake cycle, causing many to sleep less than the recommended seven hours a night (stock image)
Dr. Jain-Bing Wang, a public health expert involved in the paper, said: ‘Our study suggests that higher levels of outdoor artificial light exposure at night may be a risk factor for cerebrovascular disease.
‘We therefore advise people, especially those living in urban areas, to consider reducing that exposure to protect themselves from its potential harmful effects.’
Many people are keeping the curtains open at night because of a new wellness trend that encourages people to “wake up with the sun.”
But scientists warn that about 80 percent of the world’s population already lives in light-polluted areas, which can make it difficult for them to sleep.
Using the Bortle Dark Sky Scale, which rates the darkness of the sky from one to nine, scientists say the average moonless night has a benchmark of one – or very little light in the sky.
By comparison, major cities like New York have a reading of nine, indicating high levels of light pollution.
For the article, published today in the magazine Heart attackscientists recruited 28,300 people from the Chinese port city of Ningbo, about 200 kilometers south of Shanghai.
The participants were on average 62 years old and had no history of cerebrovascular disease, such as stroke and aneurysms.
Each was tracked for six years – from 2015 to 2021 – with scientists recording cases of stroke or other cerebrovascular disease through hospital medical records.
They discovered a total of 1,278 cases, of which 900 were strokes.
The analysis used satellite images to estimate the light pollution each patient experienced at night.
The results were adjusted by age, gender and income to suggest the risk of cerebrovascular disease from light exposure at night.
The researchers wrote in the paper: ‘Exposure to (bright light at night) could cause the body’s circadian rhythm to suppress melatonin secretion.
‘This could result in changes in biological indicators, including increased triglyceride levels… blood pressure and blood glucose, all of which are triggers for the onset of cerebrovascular disease.’
Dr. Wang added: “Despite significant progress in reducing traditional cardiovascular risk factors such as smoking, obesity and type 2 diabetes, it is important to consider environmental factors in our efforts to reduce the global burden of cardiovascular disease.”
Limitations of the article included that there were no data on indoor light exposure for participants or whether they used blackout curtains.
The research was also conducted in part in response to the Covid pandemic, which may have influenced people’s risk of disease through lifestyle changes.
The CDC recommends that everyone get between seven and nine hours of sleep every night.
The study also examined the risk of cerebrovascular disease from air pollution.
It found that those living in areas with the highest concentrations of PM10 – a tiny dust released from car exhaust – had an up to 50 percent higher risk of suffering from cerebrovascular disease compared to those exposed to the lowest levels.
Those exposed to the highest levels of PM2.5 – a smaller dust also released from cars – had a 41 percent higher risk.
And those exposed to nitrogen oxide, released from cars and industrial areas, had a 31 percent higher risk.
The researchers said there is no link between air and light pollution and the risk of cerebrovascular disease.
They explained the higher risk of air pollution in the article, adding: ‘An increased risk of haemorrhagic stroke can be achieved by provoking arterial vasoconstriction, increased blood pressure and increased susceptibility to cerebral vascular rupture by inducing endothelial dysfunction.’