Night light linked to structural heart changes, study finds

A study of over 11,000 UK Biobank participants published in the European Heart Journal found that exposure to more than 3 lux of light at night is associated with cardiac remodelling — thicker heart walls and reduced pumping efficiency — which can precede heart failure. The findings suggest light pollution may be a modifiable cardiovascular risk factor, per the researchers.

Bottom line — High nighttime light exposure was linked to a 29% higher risk of heart failure over 8–10 years, per the study.

Go deeper (6)

• Participants wore wrist light sensors for seven days; cardiac MRIs taken three years later showed left ventricular wall thickening and reduced myocardial flexibility in those exposed to over 3 lux, according to the European Heart Journal paper.
• The observed changes are consistent with cardiac remodelling, a response to chronic stress that can weaken the heart, said lead author Lu Qi of Tulane University.
• In an accompanying editorial, Thomas Münzel of University Medical Center Mainz argued that darkness should be treated as a vital sign, as essential as blood pressure control.
• The study also tracked outcomes in over 73,000 participants: high nighttime light exposure was associated with a 24% higher risk of myocardial infarction and a 33% higher risk of stroke, per the same analysis.
• Shorter sleep duration mediated 24% to 49% of the association, suggesting light disrupts sleep and thereby harms the heart, the researchers said.
• Münzel and colleagues recommended clinicians ask patients about bedroom darkness, night-shift work, and screen use, and suggested cheap fixes like blackout curtains and warm-coloured bedside lighting.

Read the reporting