Residential exposure to traffic noise and incidence of dementia in Denmark: a national cohort study.

BMJ 2021 ; 374 doi: https : //doi.org/10.1136/bmj.n1954

Commentary

This study was designed to investigate the association between long-term residential exposure to road traffic and rail noise and the risk of incident dementia.

Participants included 1,938,994 adults aged 60 years and older living in Denmark between January 1, 2004 and December 31, 2017.

The study population included 103,500 participants with incident dementia, of whom 31,219 were diagnosed with Alzheimer's disease, 8664 with vascular dementia, and 2,192 with Parkinson's disease-related dementia.

Using a Cox regression model, the average 10-year exposure to road traffic and railroad noise is maximum (L den max) and minimum (L den).

The exposed façade of the building was shown to be associated with a higher risk of dementia from all causes. This association showed a general pattern of higher hazard ratios with higher noise exposure, but a tendency for the risk to level off or decrease slightly with higher noise levels was also observed.

In the subtype analysis, both road traffic noise and rail noise were associated with a higher risk of Alzheimer's disease, with a hazard ratio of 1.16 for road L up to ≥65 decibels road L, compared with DEN <45 decibels, 1.27 for DEN min ≥55 decibels rail L, compared with <40 decibels, 1.16 for The maximum ≥60dB compared with <40dB for DEN Railway L, and the minimum ≥50dB compared with 1.24 (1.17-1.30) DEN<40dB.

These indicate that noise from road traffic, but not rail traffic, is associated with an increased risk of vascular dementia.