Noise pollution and dementia
How noisy is your lived environment? Is it increasing your risk of getting dementia?
An interesting study confirming that transportation-related exposures increase your risk of dementia. The assumption is that it is due to noise pollution. But is it?
An accompanying editorial quotes a WHO report that ‘traffic noise alone is responsible for the loss of more than one million healthy life years annually in western Europe as a result of noise-related disability and disease, including cognitive impairment’. Is it premature to assume it is the noise that is the problem rather than air pollution or lack of sleep as a result of the noise? Both air pollution and poor sleep hygiene are known risk factors for dementia.
Animal studies indicate that exposure to noise modifies some brain structures and is associated with reduced brain volume in the medial prefrontal cortex and a reduction in cortical thickness in the hippocampal and amygdala areas—all are essential components of the neural circuitry mediating stress responses.
If noise exposure does harm the ageing brain then this is another modifiable risk factor to prevent dementia. Although this study only looked at residential noise what about noise pollution at work and in other components of the lived environment? Noise pollution might affect the risk of developing other chronic disorders, such as hypertension, hearing loss, insomnia and mental health problems, which are the real risk factors for dementia.
Being exposed to noise pollution may also be linked to other social determinants of health, in particular, education and deprivation, which although taken into account in the analyses below may be associated with other factors that were missed, for example, smoking, alcohol intake, head trauma, etc.
Regardless of whether the link between noise exposure and dementia is an association or causal, it would be worthwhile doing randomised studies to see if reducing noise pollution could reduce the incidence of all-cause dementia. What do you think?
Cantuaria et al. Residential exposure to transportation noise in Denmark and incidence of dementia: national cohort study. BMJ. 2021 Sep 8;374:n1954. doi: 10.1136/bmj.n1954.
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.
Ritz & Yu. Noise exposure and dementia: a rising concern in ageing populations. Editorial BMJ. 2021 Sep 8;374:n2120. doi: 10.1136/bmj.n2120.
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General Disclaimer: Please note that the opinions expressed here are those of Professor Giovannoni and do not necessarily reflect the positions of the Barts and The London School of Medicine and Dentistry nor Barts Health NHS Trust and are not meant to be interpreted as personal clinical advice.
My father, who died with/from Alzheimer's, worked around and drove noisy farm tractors for 20 or so years (before going to work for IBM, no less). I, loved rock'n'roll and turned up the volume way too loud, often with headphones on. He was very hard of hearing years before onset, I have tinnitus (and MS). Seems that there would be many opportunities to study the phenomenon in specific noise traumatized groups. (X-rock musicians, bartenders where rock bands play, etc.)
Since MS I’ve become extremely intolerant of intrusive noise, the extra cognitive processing it demands can make it too difficult to multi-task at times. I wonder if noise affects aging or damaged (MS) brain in a different way to a healthy young one - is it only when cognitive problems already exist that noise becomes this destructive addition? Bloody love my noise cancelling headphones!