Living in a big city is associated with living with a large amount of artificial light. LED street lightsscreens, signs, traffic… great light pollution that is undoubtedly one of the most visible traces of urban progress. But this is something that not only affects biodiversity or sleep, since a study presented in the American Heart Association Scientific Sessions 2025 suggests that it could also be linked to a higher risk of cardiovascular disease.
Currently the towns are being left desolate, and the citizens are They are concentrating in the big cities because of the great job or training opportunities they have. But there are always different drawbacks, the noise being possibly very annoying (especially for sleeping and resting), but light is also something to explore.
A few weeks ago the topic of the moment was undoubtedly the time change and why experts point out that winter time is the best despite the fact that it gets dark really soon. A debate that focuses on our circadian cycles and sunlightbut we must also take into account the great exposure to artificial lights that we have, especially in large cities.
The study. The research, developed by the team of cardiologist Shady Abohashem, from Massachusetts General Hospital and Harvard Medical School, analyzed data from 466 Boston adults without active cardiac pathologies. The researchers crossed their brain scans (PET/CT) with satellite images of urban night glow from the New World Atlas of Artificial Night Sky Brightness.
The result was quite clear in this case: the higher the levels of artificial light at night where they lived, the greater the stress-related brain activity and the greater the inflammation of the arteries. Two key indicators of cardiovascular risk, which undoubtedly set off all the alarms.
If we put it into concrete figures, the risk of developing cardiovascular disease after five years is 35% higher than that of people who live in large cities. But looking at ten years, this risk stands at 22%.
Its mechanism. In order to understand the reason for this data, we have to go to the brain. When this organ detects light at night (a time when in theory there should be complete darkness), the hypothalamic stress axis is activated. This response, maintained over time, can cause inflammation throughout the body and especially atherosclerosis, as has been shown in studies on chronic stress and cardiovascular disease. This phenomenon, Abohashem suggests, would explain how a seemingly harmless environmental factor could be integrated into the cardiac risk equation.
Julio Fernández-Mendoza, expert in sleep medicine and author of the recent scientific statement of the American Heart Association on circadian and cardiometabolic healthsums it up like this: “Artificial light at night suppresses melatonin and disrupts the internal clock. This alters blood pressure, metabolism and endothelial function. This new study shows how this alteration can be observed even at the brain and arterial level.”
More evidence. But this study is not isolated, since the idea is not new and there is already literature that supports it. For example, a cohort study with more than 400,000 people in South Korea already observed that living in brighter areas increased the risk of heart attack and stroke. The same thing happened in China with a study that detected that prolonged exposure to urban light increased the incidence of coronary heart disease in older adults.
Besides, a published review in Sleep Medicine Reviews explains how artificial light can alter melatonin secretion, modify the circadian rhythm and activate low-grade inflammatory reactions in humans. In the end all the ingredients for us to expose ourselves to an alteration in our system.
What can we do? Although the new work is observational and has not yet been peer-reviewed, its authors suggest concrete measures that could have a real impact: reducing unnecessary street lighting, implementing motion sensors in residential areas, choosing warm tones (less blue) and, at home, keeping bedrooms dark and free of screens before bed.
In the end the idea is the one we have always repeated: maintain good sleep hygiene. Something that is achieved by avoiding looking at your phone minutes before going to sleep or even separating dinner from bedtime in order to maintain the best conditions for our brain.
Images | Nao Ya DESIGNECOLOGIST
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