Road Traffic Noise, Noise Difference Between Residential Facades, and Risk of Parkinson Disease.

Abstract

Importance Transportation noise has been proposed as a risk factor for Parkinson disease (PD), but epidemiological evidence remains limited and inconsistent. Objective To investigate whether long-term residential exposure to road traffic noise is associated with a higher risk of PD. Design, Setting, and Participants This was a Danish nationwide prospective cohort study with follow-up from 2000 to 2017. Danish residents 40 years and older were eligible. Analyses were conducted from April to May 2026. Exposures Based on complete residential address history from 1990 onward, 10-year time-weighted residential exposure to road traffic noise (LDEN) at the most and least exposed facades were assessed for all participants. Main Outcome and Measures Incident PD cases during follow-up were identified in the National Patient Register. Analyses were conducted using Cox proportional hazards models. Results Of 3 542 488 eligible individuals, 438 911 were excluded (prevalent PD, incomplete address history, or missing covariates), leaving 3 103 577 participants (mean [SD] baseline age, 50.9 [11.7] years, 1 588 658 female [51.2%]). Among 3 103 577 participants, 20 587 developed PD during follow-up. Road traffic noise at the most exposed facade (LDEN-Max) was associated with a hazard ratio (HR) of 1.03 (95% CI, 1.00-1.05) per interquartile increment of 11.5 dB in models adjusted for individual- and area-level sociodemographics, air pollution (fine particulate matter with a diameter of 2.5 µm or less [PM2.5] and ultrafine particles), and green space covariates. Having a difference between noise at the most and least exposed facades (Δnoise, indicator of having a quiet side) of 10 dB or more was associated with a decline in PD risk across different levels of LDEN-Max above 50 dB. Also, accounting for Δnoise strengthened the association between LDEN-Max and PD (HR, 1.06; 95% CI, 1.02-1.09). Noise at the least exposed facade was associated with PD, with an HR of 1.04 (95% CI, 1.02-1.07) per interquartile increment of 8.9 dB. Associations were consistent across strata of sex, education, income, cohabiting status, and population density and after additional adjustment for smoking and physical activity in a subpopulation. Conclusions and Relevance Results of this cohort study show that long-term exposure to road traffic noise was associated with higher PD risk. Having a quiet facade mitigated this association. These findings suggest noise as a novel risk factor for PD and support mitigation strategies ensuring a quiet residential side.