We need darkness for heart health: nights illuminated by artificial lights facilitate alterations that can favor heart failure.
Light pollution isn’t just taking away our starry skies. It could also affect cardiovascular health: excessive exposure to light at night is in fact linked to alterations to the structure and functionality of the heart.
This is suggested by the results of a study on over 11,000 people published in European Heart Journal. The research deepens and motivates the connection between nights without darkness and cardiovascular disorders which has already emerged in previous works.
Nights brightened by day
A team of scientists from Tulane University and the Harvard TH Chan School of Public Health in the United States analyzed data from 11,071 subjects included in the UK Biobank database who wore wrist devices with an integrated light sensor for 7 days between 2013 and 2015 and underwent cardiac MRI three years later.
The researchers compared the data of the participants who had been subjected to light levels higher than three lux (a unit of measurement that quantifies the illuminance, i.e. the amount of light that reaches a surface) with those of those who had almost no exposure to any light source at night.
Heart reshaped (but not for the better)
Those who had been exposed to higher levels of light at night showed signs of changes in the structure of the heart that are typically observed in those who have suffered chronic stress or after a heart injury.
Among these, a thickening of the wall of the left ventricle (one of the chambers of the heart, which when contracting pumps oxygenated blood towards the rest of the body through the aorta artery) which caused a reduction in the space of the ventricle itself; and then, changes in the right ventricle and left atrium (the atria are the two upper cavities).
Not only that: the test also showed signs of a reduction in the heart’s ability to contract while beating, an early indicator of cardiac dysfunction.
For Lu Qi, first author of the study, what was detected «is a process in which the structure and function of the heart change and which we generally observe in response to chronic stress or cardiac injury. It’s our body’s way of adapting to that stress, but it ultimately weakens the heart and can lead to heart failure.”
Shutters lowered: the doctor prescribed it!
According to the authors, it is enough to wish that the protection of night darkness is suggested by doctors who monitor cardiovascular health, and that policy makers understand that light pollution is dangerous Also for heart health: moreover, from a public health point of view, combating excessive night-time lighting is an intervention that can be pursued with simple measures and low costs.
Scientists also hope that those who care about heart health, and in particular patients with heart failure (a chronic condition in which the heart cannot pump enough blood) or atrial fibrillation (the most common heart arrhythmia), will regularly ask patients how dark their nights are. Questions like: what time does he turn off the TV or cell phone? Lower the shutters? How dark is his room? they may be more important than you think.
