“The effect sizes are modest in absolute terms but consistent, dose-dependent, and observed across every cardiac chamber — which is what makes them noteworthy,” said Thomas Münzel, MD.
“Compared with no nighttime light exposure above 3 lux, the highest-exposure group showed 2.4% greater LV mass, 1.5% greater wall thickness, 1.9% lower myocardial contraction fraction, and roughly 3% reductions in circumferential, radial, and longitudinal strain, plus right ventricular and left atrial changes,” he said.
These aren’t hypothetical: in the parallel outcomes analysis of over 73,000 participants followed 8–10 years, the same exposure gradient tracked with a 29% higher risk of heart failure, 24% higher risk of myocardial infarction, 33% higher risk of stroke, and 26% higher cardiovascular mortality.
Münzel likened the health impact of this to living under a flight path, a recognized environmental cardiovascular risk factor, and said nighttime light exposure is a serious, independent cardiovascular risk factor with no safe lower limit.
“The important caveat: this remains observational data, so causation isn’t proven, and the absolute individual-level risk from light exposure alone is small next to established factors like hypertension or smoking. Its significance is more than it identifies a previously invisible, modifiable contributor sitting alongside the exposures we already screen for,” he added.
