Sleeping with lights on may raise risk of heart disease, says new study

Exposure to bright light at night may disrupt circadian rhythm and increase the risk of heart failure, stroke, and arrhythmias, particularly in women

Do you often fall asleep with the lights or TV on? This habit might be hurting your health. A new study has found a significant link between night-time light exposure and increased risk of heart conditions like heart failure, stroke, and irregular heartbeat.

 

The study, titled Personal night light exposure predicts incidence of cardiovascular diseases in >88,000 individuals, published on medRxiv, was conducted by researchers from the Flinders Health and Medical Research Institute in collaboration with scientists from the UK and the US. It analysed personal light exposure data from over 88,000 individuals aged above 40 using wrist-worn light sensors.

Why is night-time light exposure risky for the heart?

The preliminary findings suggest that sleeping with lights on interferes with the circadian rhythm — the body’s internal 24-hour biological clock. This clock regulates sleep-wake cycles, blood pressure, glucose metabolism, heart rate, and hormone release.

 

According to the researchers, artificial light at night disrupts these functions, leading to metabolic changes, inflammation, and vascular damage that can raise the risk of cardiovascular disease.

 

They highlighted several mechanisms:

• Disrupted circadian rhythm affects glucose metabolism, increasing insulin resistance and diabetes risk 
• Light-induced hypercoagulability may raise the likelihood of strokes and heart attacks 
• Persistent elevation in night-time blood pressure can damage the heart and vessels 
• Conflicting signals to the heart’s pacemaker nodes can trigger arrhythmias

What did the study reveal about cardiovascular risks?

Based on 13 million hours of light exposure data from 88,905 UK Biobank participants, the study found that those in the brightest night-time light exposure group (top 10 per cent) had significantly higher cardiovascular risks than those in the lowest group:

• 23–32 per cent higher risk of coronary artery disease 
• 42–47 per cent higher risk of myocardial infarction 
• 45–56 per cent higher risk of heart failure 
• 28–32 per cent higher risk of atrial fibrillation 
• 28–30 per cent higher risk of stroke

Who is more vulnerable to night-time light exposure?

The study found that women had a stronger correlation between night-time light exposure and heart failure or coronary artery disease. Younger individuals were also more susceptible to heart failure and arrhythmias.

 

These findings suggest that factors like age, sex, and lifestyle may heighten vulnerability to the cardiovascular impacts of night-time light exposure.

How can you reduce the risks from night-time lighting?

Avoiding bright light exposure while sleeping could help lower your heart disease risk. Experts recommend:

• Using blackout curtains or eye masks at night 
• Switching to warm, dim lighting in the evenings 
• Avoiding falling asleep with the TV or phone screen on
• Opting for low-intensity, circadian-friendly night lights for safety

“Robust circadian rhythms are vital for healthy cardiovascular function,” the researchers concluded, adding that “disruptive effects of night light on circadian rhythms may lead to dysregulation of various cardiovascular and metabolic mechanisms.” 

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This content is for informational purposes only and is not a substitute for professional medical advice.