Metabolic profiles of nighttime road traffic noise exposure: A multi-cohort study in the European LongITools project

Background: Traffic noise has been associated with the risk of cardiometabolic diseases. Identifying internal exposome factors, such as metabolomic biomarkers, associated with traffic noise in the general population may help clarify the pathophysiological pathways linking noise to cardiometabolic outcomes. To address this gap, we investigated the relationships between nighttime road traffic noise and systemic metabolic biomarkers. Methods: This study included 272,229 European adults, aged 31 years and over, from the UK Biobank (UKBB), the Rotterdam Study (RS), and the Northern Finland Birth Cohort 1966 (NFBC1966). Annual average nighttime road traffic noise was linked to the individual residential address at the time of blood sampling, using national noise maps. We utilized high-throughput nuclear magnetic resonance metabolomics to profile 155 biomarkers (including lipids, lipoproteins, fatty acids, and other low-molecular-weight metabolites). In discovery analyses in UKBB, we applied linear models adjusted for age, sex, education, and fine particulate matter to identify significant biomarkers (Bonferroni P < 0.003125). The associated biomarkers were further assessed using multilevel random-effects meta-analysis across the UKBB, RS, and NFBC1966. Results: From the discovery analysis, nighttime road traffic noise (≥55 dB versus <45 dB) was associated with higher levels of 48 metabolites in the UKBB. Associations for 20 metabolites remained robust in meta-analysis and through sensitivity analyses. Noise (≥55 dB) was associated with elevated circulating concentrations of cholesterol-related biomarkers, including lipids in esterified cholesterol-enriched lipoproteins such as low-density lipoprotein (LDL) and intermediate-density lipoprotein (IDL), as well as unsaturated fatty acids and membrane biomarkers. Except for two unsaturated fatty acids, these biomarkers showed a monotonic exposure-response pattern from 50 dB onward. Conclusion: This study provides evidence that nighttime road traffic noise exposure from 50 dB upward is associated with alterations in blood cholesterol and lipid profiles in adults. This finding may clarify the association between traffic noise and cardiometabolic diseases.