Transportation noise exposure and incident type 2 diabetes: A retrospective cohort study in a large U.S. healthcare system

OBJECTIVE: Transportation noise is increasingly recognized as a cardiometabolic stressor, but its relationship with type 2 diabetes mellitus (T2DM) remains poorly defined. We examined whether transportation noise exposure was associated with incident T2DM in a large, diverse U.S. healthcare system cohort. METHODS: We identified adults without baseline T2DM from the Houston Methodist Learning Health System Registry (2016-2023). Transportation noise exposure was assigned at the census block group level using the 2020 U.S. Department of Transportation National Transportation Noise Map. Five noise categories were examined: Road, Rail, Aviation, Road plus Aviation and Total. Cox proportional hazards models estimated associations across predefined categories, Quiet (≤45 dB), Moderate (45-54 dB) and Loud (≥55 dB), and per 10 dB increase, adjusting for demographics, cardiometabolic risk factors, socioeconomic vulnerability and PM₂.₅. RESULTS: Among 984 658 adults (2.1 million person-years), 39 587 developed T2DM (1.88 per 100 person-years). Loud rail noise (HR 1.14; 95% CI: 1.01-1.29) and loud total noise (HR 1.17; 95% CI: 1.03-1.33) were associated with higher T2DM risk. Continuous models showed similar patterns, with each 10 dB increase in rail noise (HR 1.09; 95% CI: 1.05-1.13) and road noise (HR 1.04; 95% CI: 1.01-1.08) associated with a higher hazard of incident T2DM. Effect sizes were modest but internally consistent and aligned with prior environmental noise studies. CONCLUSION: Transportation noise, particularly rail noise, was associated with higher T2DM risk. Given plausible mechanisms involving sleep disruption and stress-related neuroendocrine activation, these findings add to evidence linking environmental noise to metabolic health and motivate further studies to evaluate causality and potential benefits of noise mitigation.