A study published in the European Heart Journal has linked higher nighttime light exposure to measurable changes in heart structure and a higher long-term risk of cardiovascular disease. Researchers at Tulane University's School of Public Health and Tropical Medicine analysed UK Biobank data, using wrist-worn light sensors worn for one week by 11,071 participants between 2013 and 2015, followed by cardiovascular magnetic resonance scans roughly three years later. A separate group of 73,286 participants was tracked for eight to ten years of health outcomes. People with the highest nighttime light exposure, above 3 lux, showed greater left ventricular mass and wall thickness, along with weaker measures of how well the heart muscle contracts and relaxes. Over follow-up, this group had a 29% higher risk of heart failure, a 15% higher risk of atrial fibrillation, a 24% higher risk of heart attack, a 33% higher risk of stroke, and a 26% higher risk of cardiovascular death, compared with those exposed to the least light at night.
What the researchers say limits the findings
The study is observational, so it cannot show that light exposure itself causes heart changes, only that the two are linked. Light was measured for a single week, which may not reflect a person's usual exposure over months or years, and wrist sensors record ambient light rather than what reaches the eyes. There was also a gap of around three years between the light measurements and the heart scans. Shorter sleep duration explained only 24% to 49% of the association, meaning other factors may be involved.
What this means for you
This is a story about environmental light exposure, not a product ingredient, so it does not translate into a supplement recommendation. The findings describe an association between higher nighttime light and heart structure changes seen on a scan, not proof that changing bedroom lighting changes an individual's risk. Anyone with an existing heart condition, or concerns raised by findings like this, should speak to their GP or pharmacist rather than infer personal risk from a single observational study.
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