Residential exposure to transportation noise in Denmark and incidence of dementia: national cohort study
BMJ 2021; 374 doi: Residential exposure to transportation noise in Denmark and incidence of dementia: national cohort study (Published 09 September 2021) Cite this as: BMJ 2021;374:n1954Abstract
Objective To investigate the association between long term residential exposure to road traffic and railway noise and risk of incident dementia.
Design Nationwide prospective register based cohort study.
Setting Denmark.
Participants 1 938 994 adults aged ≥60 years living in Denmark between 1 January 2004 and 31 December 2017.
Main outcome measures Incident cases of all cause dementia and dementia subtypes (Alzheimer’s disease, vascular dementia, and Parkinson’s disease related dementia), identified from national hospital and prescription registries.
Results The study population included 103 500 participants with incident dementia, and of those, 31 219 received a diagnosis of Alzheimer’s disease, 8664 of vascular dementia, and 2192 of Parkinson’s disease related dementia. Using Cox regression models, 10 year mean exposure to road traffic and railway noise at the most (Ldenmax) and least (Ldenmin) exposed façades of buildings were associated with a higher risk of all cause dementia. These associations showed a general pattern of higher hazard ratios with higher noise exposure, but with a levelling off or even small declines in risk at higher noise levels. In subtype analyses, both road traffic noise and railway noise were associated with a higher risk of Alzheimer’s disease, with hazard ratios of 1.16 (95% confidence interval 1.11 to 1.22) for road Ldenmax ≥65 dB compared with <45 dB, 1.27 (1.22 to 1.34) for road Ldenmin ≥55 dB compared with <40 dB, 1.16 (1.10 to 1.23) for railway Ldenmax ≥60 dB compared with <40 dB, and 1.24 (1.17 to 1.30) for railway Ldenmin ≥50 dB compared with <40 dB. Road traffic, but not railway, noise was associated with an increased risk of vascular dementia. Results indicated associations between road traffic Ldenmin and Parkinson’s disease related dementia.
Conclusions This nationwide cohort study found transportation noise to be associated with a higher risk of all cause dementia and dementia subtypes, especially Alzheimer’s disease.
People who live next to main roads often claim that they "get used to it" but maybe it's their brain cells dying or they just forget what it's like to live in peace. The air pollution probably doesn't help either.