The light at night is an invisible source of stress for the body which responds by inflaming the vessels, and increasing the risks for the heart.
The light from the street lamps that filters through the shutters at night could be more than just a nuisance. In the long run, it risks damaging heart health: preliminary research presented recently at a conference of the American Heart Association has found a link between nocturnal exposure to light pollution and increased stress-related brain activity, and between this and inflammation of the arteries and a higher risk of heart disease.
The analysis could explain why it has long been said that exposure to light during sleeping hours is harmful to heart health.
Satellites and instrumental tests
The study from Massachusetts General Hospital and Harvard Medical School in Boston explored the relationship between light pollution and heart health by taking advantage of the World Atlas of Artificial Night Sky Brightness, a global map of brightness from artificial sources captured thanks to measurements from Suomi NPP, a meteorological satellite from NOAA, the National Oceanic and Atmospheric Administration in the United States.
The scientists measured the nighttime light exposure of 466 adults with a median age of 55 years between 2005 and 2008, during which time the participants underwent regular PET and CT scans. PET (positron emission tomography) reveals metabolic activity in tissues, while CT scan provides a detailed X-ray anatomical photograph of them: by combining the two techniques it was possible to monitor how the brain responded to this source of stress and the level of tissue inflammation.
A stress for the eyes and the heart
Those subjected to more light pollution were also found to have higher levels of brain stress responses and had poorer cardiovascular health overall, with an increased risk of heart problems. This risk was assessed by cardiologists who did not have access to data on light exposure, and therefore were not aware of this disturbing element.
The increased risk for the heart has grown along with the increase in exposure to light. Each standard deviation (a statistical measure that indicates how much the data in a set deviates from their mean) of growth in light exposure was associated with a 35% increased risk of heart disease within 5 years, and 22% in the following 10 years. This association “held up” even when other environmental factors that can harm the heart were taken into consideration, such as noise pollution or living in disadvantaged socioeconomic contexts.
Darkness and light: the heart needs regular rhythms
The research, which has yet to be published in detail in a scientific journal, suggests that one of the possible disturbing factors caused by night light for the heart may be the brain’s response to it, a stress reaction that increases inflammatory processes and in the long run hardens the arteries. It will be necessary to intervene both at a municipal level, with strategies to reduce light pollution, and at a personal level with greater care in maintaining darkness in the bedroom.
