# 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

## TL;DR

This study shows that even low-level nighttime road traffic noise can harm cardiovascular health and sleep in healthy adults.

## Contribution

The study provides direct evidence linking acute night-time road traffic noise to impaired vascular function and immune signaling in humans.

## Key findings

- FMD decreased significantly after exposure to 30 and 60 road traffic noise events.
- Noise exposure increased heart rate and reduced self-reported sleep quality.
- Proteomic analysis showed noise-related changes in immune signaling pathways.

## Abstract

Road traffic noise is the dominant source of environmental noise in Europe and a recognized cardiovascular risk factor, yet direct mechanistic evidence from human studies remains limited. This study investigated the acute effects of low-level night-time road traffic noise exposure on cardiovascular parameters in healthy adults.

In a randomized, double-blind, crossover design, 74 healthy participants were exposed to three overnight conditions: control (no noise, average sound pressure level (LAeq) 30.70 dB), 30 (LAeq 41.36), and 60 (LAeq 44.13) recorded road traffic noise events (peak level ≈60 dB). The primary endpoint was endothelial function assessed by flow-mediated dilation (FMD) the morning after each night; a subgroup received vitamin C to assess oxidative stress involvement. Secondary endpoints included sleep quality (questionnaires), cardiovascular parameters (blood pressure, heart rate, electrocardiogram), and targeted proteomic analysis (Olink panels). FMD significantly decreased from 9.35% (control) to 8.19% after 30 noise events (Δ = 1.16%, P = 0.005) and 7.73% after 60 events (Δ = 1.63%, P < 0.0001), with the strongest FMD improvement by vitamin C in the 60-event condition (Δ = 1.02%). Noise exposure increased heart rate (mean difference Δ = 1.23 bpm, P = 0.04; max Δ = 7.95 bpm, P < 0.001) and the odds of post-noise heart rate peaks (odds ratio 2.42, 95% confidence interval 2.07–2.83). After noise exposure, self-reported sleep quality and restfulness were significantly impaired across all dimensions. Clinical chemistry blood parameters did not change significantly. Proteomic analysis revealed noise-associated changes in interleukin signalling and chemotaxis in participants with the strongest FMD impairments.

Acute exposure to night-time road traffic noise leads to measurable changes in cardiovascular health parameters in healthy adults. These effects were linked to activation of molecular pathways of immune signalling. Plasma proteome changes were correlated to FMD changes (responders vs. non-responders), highlighting interindividual biological susceptibility to noise.

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