October 21, 2020

expert reaction to study looking at long term noise exposure and associated cognitive decline and dementia in older adults

Research, published in Alzheimer’s & Dementia, looked at long term noise exposure and associated cognitive decline and dementia in older adults.

Dr Rosa Sancho, Head of Research at Alzheimer’s Research UK, said:

“There are nearly one million people in the UK living with dementia and it’s caused by devastating diseases.

“This new US-based research suggests a link between noisier areas to live and early-stage thinking problems, but if any causal link exists between these two factors, it is not confirmed by this study.

“The researchers estimated the noise levels someone experienced with readings taken during the daytime and during non-rush hour traffic, ten years ago in the US, so it’s difficult to say whether this research maps to the lives of people in the UK.

“Research has already implicated hearing loss in midlife as a risk factor for dementia and as the diseases causing dementia develop in the brain up to two decades before symptoms show, understanding what may be causing this link will be crucial for further research.

“While we can’t know from this study whether reducing noise pollution could reduce people’s dementia risk, policies to tackle this could have many other benefits for people living in noisy areas. For reducing dementia risk, the best current evidence indicates staying physically and mentally active, eating a healthy balanced diet, not smoking, drinking only within the recommended limits and keeping weight, cholesterol and blood pressure in check.”

Dr Byron Creese, from the University of Exeter Medical School, said:

“The study links neighbourhood noise levels with higher prevalence of Alzheimer’s disease and Mild Cognitive Impairment.  It adds to growing evidence suggesting that the environment in which we live might impact our dementia risk.  However, like any observational study we cannot be sure of causality – we do not know from this study that higher noise levels cause Alzheimer’s disease or Mild Cognitive Impairment.  The authors controlled for a number of important lifestyle and socio-economic variables in their analysis, which increases confidence in the findings.  However, they did not measure a number of key medical conditions (e.g. blood pressure, diabetes and hearing loss) which are known to influence risk of dementia and may be more prevalent in those living in areas urban high noise areas. The average age of the sample was around 74 so we cannot be sure from this study of the impact of noise levels on people younger than this.”

Prof Carol Brayne, Professor of Public Health Medicine, University of Cambridge, said:

“Residual confounding due to societal inequalities is very hard to reduce altogether in analyses and it is possible that at least some of the findings might suffer from this bias. People who live their lives, and have their employment in very noisy settings are also more likely to have experienced disadvantage throughout their life course. Many of the risk factors that have been found to increase our risk of dementia as we age are heavily associated with social disadvantage – from education to obesity. We need policies to address all these across the life course to ensure healthy brains, in which good quality housing, environments and employment play a major part.”

Dr Llwyd Orton, Senior Lecturer in Neurophysiology, Manchester Metropolitan University, said:

“Importantly, the study did not measure noise exposure, this was estimated by a model. This is clear in the paper but not in the press release, which suggests noise was directly measured.

In addition, the study did not measure auditory function in the participants, so the individual level of hearing loss associated with noise exposure was not accounted for.

“This work fits with increasing evidence for an association between noise exposure and negative impacts on cognition and these findings largely generalise across the globe. Prospective, longitudinal studies are needed that combine audiological and cognitive measures to provide better quality of evidence.

“Other factors that may explain the finding that cannot be discounted include greater pollution sources other than oxides of nitrogen and associated higher rates of cardiovascular disease and diabetes in areas with higher noise exposure, which are known to impact cognition.”

‘Long-term community noise exposure in relation to dementia, cognition, and cognitive decline in older adults’ by Jennifer Weuve et al. was published in Alzheimer’s & Dementia at 5:01 UK time on Wednesday 21 October.

DOI: 10.1002/alz.12191

Declared interests

Dr Byron Creese: No declarations of interest

Prof Carol Brayne: No declarations of interest

Dr Llwyd Orton: No declarations of interest

None others received.