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. 2021 Sep 8:374:n1954.
doi: 10.1136/bmj.n1954.

Residential exposure to transportation noise in Denmark and incidence of dementia: national cohort study

Affiliations

Residential exposure to transportation noise in Denmark and incidence of dementia: national cohort study

Manuella Lech Cantuaria et al. BMJ. .

Abstract

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.

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Conflict of interest statement

Competing interests: All authors have completed the ICMJE uniform disclosure form and declare: MLC and JHV report grants from the William Demant Foundation during the conduct of the study. JHV also received grants from Innovation Fund Denmark and William Demant Foundation, and a joined grant from Hearing aid Industry (Oticon, WSA, GN Hearing), outside the submitted work; no other support for the submitted work; no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

Figures

Fig 1
Fig 1
Associations between 10 year mean exposure to road traffic and railway noise at the most (Ldenmax) and least (Ldenmin) exposed façades of buildings and risk of all cause dementia, using the fully adjusted model (model 2). Figure shows hazard ratios and corresponding 95% confidence intervals
Fig 2
Fig 2
Associations between 10 year mean exposure to road traffic noise at the most and least exposed façades of buildings and risk of dementia subtypes, using the fully adjusted model (model 2). Figure shows hazard ratios and corresponding 95% confidence intervals
Fig 3
Fig 3
Associations between 10 year mean exposure to road traffic noise at the least exposed façade of buildings and risk of incident all cause dementia according to sex, population density, type of building, income, calendar year, and comorbidity. Figure shows hazard ratios and corresponding 95% confidence intervals

Comment in

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