Using smartphones or being exposed to other sources of bright light before sleep may increase the risk of developing life-threatening cardiovascular diseases, Daily Mail reports, citing a study by the American Heart Association (AHA).

“We found an almost linear relationship between nighttime exposure to artificial light and heart disease: the greater the exposure, the higher the risk,” said Dr. Shadi Abouhashim, head of cardiac PET/CT research at Massachusetts General Hospital, in an interview with the newspaper.

According to RIA Novosti, the brain perceives bright light as a form of stress, triggering signals that can cause an immune response and inflammation of blood vessels. This, in turn, may lead to atherosclerosis and increase the risk of fatal conditions such as heart attack and stroke, the doctor explained.

The study involved 466 adults under the age of 55 who underwent PET/CT scans at Massachusetts General Hospital. Data on nighttime light exposure were compared with satellite images showing the levels of artificial lighting around their homes. By 2018, 17% of the participants had developed serious cardiovascular diseases.

Researchers concluded that even a slight increase in nighttime light exposure is associated with greater strain on the brain and arteries. They recommended limiting artificial light at night, sleeping in complete darkness, and avoiding the use of phones or TVs before bedtime.