Exposure to Bright Light at Night Increases Heart Disease Risk
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STORY AT-A-GLANCE
Exposure to artificial light at night disrupts your body’s natural sleep-wake rhythm, raising your risk of heart disease, heart attack, stroke, and heart failure
A large-scale study found that adults living in the brightest nighttime environments had up to a 56% higher risk of heart failure and a 47% higher risk of heart attack compared to those in the darkest settings
When combined with air pollution, bright night environments amplify cardiovascular risk even more — nighttime light accounted for up to 39% of the extra heart failure risk linked to polluted air
Nighttime light not only harms your heart but also increases the risk of mental health disorders, including depression, anxiety, PTSD, and bipolar disorder, while reducing exposure to bright daylight worsens these effects
Restoring a natural light-dark cycle — bright days and truly dark nights — helps regulate your hormones, protect your heart, improve mood, and reduce your risk of chronic disease
Light is supposed to signal your body that it’s time to rest, yet most people now sleep surrounded by it — streetlights streaming through the window, the glow of electronics, the standby light on the TV. What seems harmless is, in fact, an invisible stressor on your heart. Mounting evidence shows that artificial light at night interferes with your body’s ability to repair and regulate itself, setting the stage for the very diseases most people try to avoid through diet and exercise.
Heart disease — narrowed or hardened arteries that restrict blood flow — is influenced by poor lifestyle habits. But research suggests your nighttime environment plays a powerful role, too. When your internal clock is thrown off by light exposure, it triggers a cascade of changes: blood pressure creeps up, heart rate climbs, and inflammation rises. Over time, these small disruptions become the foundation for serious cardiovascular problems.
True recovery happens only in darkness. That’s when your body restores rhythm, balances hormones, and gives your heart a chance to rest. Yet for many people, that natural cycle is elusive. The simple act of dimming the light after sunset could make the difference between heart health and heart strain — and recent studies are revealing just how strong that connection really is.
Light Exposure at Night Linked to Cardiovascular Disease
A study published in JAMA Network Open analyzed about 13 million hours of light data from 88,905 adults aged 40 and older to determine whether brighter light at night increased cardiovascular disease risk.1
Over a 9.5-year follow-up period, researchers found that participants exposed to the brightest nighttime environments were significantly more likely to develop coronary artery disease, heart attack, heart failure, atrial fibrillation, and stroke. Those with the brightest nights — defined as the top 10% of nighttime light exposure — had up to a 56% higher risk of heart failure and 47% higher risk of heart attack compared to those with the darkest nights.
The participants represented real-world living conditions across the U.K. — This research tracked individuals in their natural environments using wrist-worn light sensors instead of relying on satellite imagery. By following real people over time rather than relying on lab-based light exposure or self-reports, the study provided some of the most compelling evidence yet that the artificial glow surrounding us at night is harming our hearts.
The more light participants were exposed to at night, the higher their risk of heart disease became — Those in the middle exposure range had slightly elevated risks, while those in the top range faced dramatically higher odds. For example:
32% higher risk of coronary artery disease
32% higher risk of atrial fibrillation (an irregular heartbeat)
28% higher risk of stroke
Women and younger adults were the most affected — The study found that women and younger adults faced stronger effects from nighttime light exposure. The biological reason may lie in sex-specific circadian sensitivity — women’s internal clocks are more reactive to light signals, meaning that a small disruption causes larger hormonal and cardiovascular effects.
<label class="hide-text" contenteditable="false">Text within this block will maintain its original spacing when published</label>Similarly, younger adults have greater circadian responsiveness, which fades with age, making them more vulnerable to nighttime light’s biological disruptions.
Light exposure at night confuses your body’s master clock — This is located in a brain region called the suprachiasmatic nucleus, which normally signals the release of melatonin, a hormone that promotes sleep and helps regulate blood pressure, blood sugar, and heart rate. When this rhythm is disturbed:
Heart rate increases when it should be at rest.
Blood pressure rises and stays elevated through the night.
Inflammatory pathways activate, damaging blood vessels over time.
The heart muscle becomes less efficient, leading to structural changes such as thickening of the walls and reduced pumping strength.
Daytime light exposure had the opposite effect, offering protection — Participants exposed to brighter light during the day showed lower risks of coronary artery disease, heart failure, and stroke.
<label class="hide-text" contenteditable="false">Text within this block will maintain its original spacing when published</label>This highlights the importance of maintaining strong light-dark contrast: getting enough bright light in the morning and daytime while keeping nights as dark as possible. Your body’s internal rhythm depends on this contrast to maintain healthy cardiovascular and metabolic function.
Night Light and Dirty Air Team Up to Hurt Your Heart
For a study published in the Journal of the American Heart Association, researchers tracked 416,032 adults for almost 15 years and looked at air pollution and nighttime light around their homes to see who developed heart and blood vessel problems like heart attacks, heart failure, irregular heartbeat, stroke, or died from heart disease.2
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