Sleeping under realistic noise conditions
In order to investigate the acute effects of road traffic noise on the 74 study participants, the researchers simulated different levels of exposure: one night without additional noise and one night each with 30 and 60 road traffic noise events at an average volume of 41 to 44 decibels for 1 minute and 15 seconds each. The noise exposure occurred every 11.5 or 9.5 minutes via loudspeakers in the participants' private bedrooms. The next morning, the researchers evaluated the cardiovascular measurements from the night, analyzed blood samples for proteins involved in inflammatory processes, and examined the elasticity of the blood vessels. In the controlled, randomized, double-blind study, neither the participants nor the researchers who performed the measurements knew what sound levels they had been exposed to during the night.
Variation in individual noise sensitivity
The participants who were exposed to the noise sequences reported a perceived decline in sleep quality. Their reactions to the noise varied, indicating individual sensitivity to noise. Using a combination of heart rate analysis, molecular blood tests, and vascular measurements, the researchers were able to detect both functional and biological changes, which confirmed the reported impairment – even after just one night: Heart rate increased after individual noise events, changes in immune and inflammation-associated proteins were observed in the blood, and ultrasound measurements confirmed reduced blood vessel elasticity. This endothelial function in particular is considered an early warning sign for vascular health. “Our study findings could explain the molecular disease mechanisms triggered by noise in humans,” emphasizes Professor Daiber, head of the Molecular Cardiology research group at the Department of Cardiology at the University Medical Center Mainz.
11 million Germans are exposed to noise at night
The authors of the study advocate consistent noise protection measures, such as 30 km/h speed limits in urban areas and more green spaces as natural sound barriers. “Noise protection is heart protection,” emphasizes Professor Münzel. "Every decibel reduction means less stress on blood vessels, less inflammation in the blood – and, in the long term, fewer heart attacks and strokes. Urban planning is therefore not an aesthetic issue, but a cardiovascular prevention strategy. Healthy cities are quiet cities." Further research is needed to better understand how the results of this short-term study might be related to the long-term risk of cardiovascular disease, say the study authors. According to the UBA, more than 11 million people in Germany are exposed to nighttime traffic noise of at least 50 decibels.
Original publication: Hahad O., et al., A randomized, double-blind, crossover study of acute low-level night-time road traffic noise: effects on vascular function, sleep, and proteomic signatures in healthy adults, Cardiovascular Research, February 2026.
Source: Press release Mainz University Medical Centre
