Artificial light at night might disrupt more than sleep. A new study suggests it can also link to changes in the heart’s structure and function, potentially increasing the risk of cardiovascular diseases. Researchers from Tulane University found that greater exposure to night light was associated with signs of adverse cardiac remodeling and reduced heart function. These findings were published in the European Heart Journal on September 9.
Cardiovascular diseases are the leading cause of death globally. In the U.S., one person dies from cardiovascular disease every 34 seconds, emphasizing the importance of understanding potential prevention measures.
Study Details
The team analyzed data from over 11,000 UK Biobank participants who wore wrist devices to monitor nighttime light exposure over seven days. Participants then underwent cardiovascular magnetic resonance (CMR) imaging to assess their hearts’ structure and performance.
Researchers found those exposed to higher nighttime light levels had increased heart muscle mass and thicker heart walls, changes that can precede cardiovascular disease. They also showed signs of impaired heart function affecting both sides of the heart.
Dr. Lu Qi, study lead and director of the Tulane University Obesity Research Center, mentioned that nighttime light exposure might affect the heart partly by reducing sleep duration and quality. Nighttime light is believed to disrupt the body’s circadian rhythm, impacting various systems.
Light Pollution Explained
Light pollution refers to excessive or unwanted artificial light in the environment. Common sources include streetlights, illuminated buildings, vehicle headlights, electronic devices, and outdoor advertising.
Past studies connected nighttime light exposure with obesity, hypertension, diabetes, and increased cardiovascular disease risk. Some research attributes this to impaired cardiac autonomic regulation, elevated systemic inflammation, and circadian rhythm disruption.
“Every cell in our body possesses a molecular circadian clock that orchestrates biological processes, ensuring these happen at the correct time of day,” said Martin Young, a professor of medicine at the University of Alabama at Birmingham. He was not involved in the study.
Young added that circadian clocks are “very sensitive to the environment, particularly light,” meaning “light exposure at the ‘wrong’ time, such as at night, can disrupt molecular clocks,” resulting in a “loss of temporal synchronization between different cells and organs within the body.”
Symptoms of Cardiovascular Diseases
Cardiovascular disease is an umbrella term for conditions affecting the heart and blood vessels, so symptoms vary depending on the condition. Common warning signs include:
- Chest pain or discomfort
- Stomach pain like indigestion
- Shortness of breath
- Tightness in the throat
- Dizziness or fainting
- Heart palpitations
- Extreme fatigue
- Swelling in the legs, ankles, or feet
Expert Opinions
“The importance of this study cannot be overstated,” Young said.
He noted researchers have long known that environmental factors and behaviors reducing sleep or impairing natural circadian rhythms increase risk for various cardiometabolic diseases, including obesity, diabetes, hypertension, stroke, and heart attacks. The findings stress the “urgent need to understand how factors like light exposure at night increase our disease risk.”
Young advised reducing light exposure at night. If not possible, blocking the blue light wavelength impairing sleep and circadian rhythms is a viable alternative. He also suggested methods to “resynchronize” clocks, like exposure to light, having a decent breakfast, and being physically active in the morning to help reset and align bodily clocks.