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 (L den max) and least (L den min) 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 L den max ≥65 dB compared with <45 dB, 1.27 (1.22 to 1.34) for road L den min ≥55 dB compared with <40 dB, 1.16 (1.10 to 1.23) for railway L den max ≥60 dB compared with <40 dB, and 1.24 (1.17 to 1.30) for railway L den min ≥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 L den min 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.
Bibliografisk noteFunding Information:
11Department of Clinical Research, University of Southern Denmark, Odense, Denmark 12OPEN, Odense Patient data Explorative Network, Odense University Hospital, Odense, Denmark 13BRIDGE, Brain Research - Inter-Disciplinary Guided Excellence, Department of Clinical Research, Faculty of Health Sciences, University of Southern Denmark, Odense, Denmark 14Department of Natural Science and Environment, Roskilde University, Roskilde, Denmark Contributors: MS, MLC, JHS, FBW, LW, ERP, OR-N, JDT, and AHP conceived and designed the study and contributed to the methodology definition. JDT, AHP, MS, and OR-N contributed to exposure assessment. MK and JK geocoded addresses and estimated air pollution. VHV geocoded addresses and estimated proportion of green space. MS, OR-N, and AHP acquired health and confounder data. MLC classified register data and conducted the statistical analysis. MLC and MS wrote the first draft of the manuscript. All authors commented and contributed to the interpretation of results and the final manuscript. The corresponding author attests that all listed authors meet the authorship criteria. Funding: This work was funded by the William Demant Foundation (grant No: 18-0964) and the Independent Research Fund Denmark (grant No: 7016-00036B). The funders had no role in the design and conduct of the study; collection, analysis, and interpretation of data, writing of the manuscript, and decision to submit the manuscript for publication.
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. Data sharing: As this study is based on data from the Danish national registers, which belong to the Danish Ministry of Health and Statistics Denmark, the authors are not allowed to share data in raw form.