Residential exposure to road and railway traffic noise and incidence of dementia: The UK Biobank cohort study.

Background: Evidence linking noise pollution and brain health, particularly at mid-to-late life, remains scarce. We investigated the associations between long-term exposure to road and railway traffic noise and incident dementia in the UK Biobank cohort.

Methods: Participants with available data for dementia incidence and linked traffic noise exposure during follow-up were included. Residential road traffic noise from both minor and major roads were calculated in accordance with CNOSSOS-EU framework; railway noise estimates were created by Extrium, with the raster datasets representing noise contributions from major railway corridors. Cox regression was used to quantify the associations between transport noise and incident dementia (incl. its subtypes), adjusting for potential confounders, air pollution and greenness.

Results: Of the full cohort (n = 502,416), 7668 participants had incident dementia during a median follow-up period of 9.67 years. No associations were found between all cause dementia incidence and road or railway noise. However, a 10-dB (dB) higher exposure in annual mean road traffic noise (Lden) was significantly associated with incident Alzheimer's disease (HR:1.150, 95 % CI: 1.022-1.294). The effect estimate was slightly higher when participants were exposed to night-time road noise above 45 dB (HR:1.188, 95 % CI:1.012-1.394) and this was mediated by the cardiovascular health profile. Railway noise (Lden) was significantly associated with incident Parkinson's disease related dementia (HR:1.042, 95 % CI:1.005-1.081), however, the effect estimate was slightly reduced after further adjustment of air pollution and residential greenness (HR:1.037, 95 % CI:0.998-1.077).

Conclusions: Distinct associations between different traffic noise exposures and incident dementia subtypes were found in this large UK prospective cohort study.