New research: Traffic noise increases the risk of dementia
You have a significantly higher risk of developing dementia if you are exposed to noise from a nearby road or railway track over an extended period of time. And the louder the noise, the greater your risk of developing dementia.
This is the finding of a major Danish research project in which researchers from the University of Southern Denmark (SDU), together with researchers from Roskilde University, Odense University Hospital and the University of Copenhagen, have demonstrated a link between noise and the development of dementia diseases such as Alzheimer's.
The Danish research results have been published today in the respected British Medical Journal.
"Traffic noise is a serious problem. It is harmful to our health, and it is generally an overlooked social problem. Now our latest research has shown that there is also a link between traffic noise and dementia. The body recovers while we sleep, and it doesn’t get the same opportunity when it’s exposed to traffic noise. This is a problem we need to address, both as researchers and as a society" says one of the researchers behind the study, Mette Sørensen, noise expert and adjunct professor at Roskilde University.
Among other things, the research results show that people have a 27% increased risk of developing Alzheimer’s disease and an 18% increased risk generally of developing dementia if they are exposed to traffic noise above 55 decibels over a number of years. Looking at the number of dementia cases, this means that of the 8,475 cases in 2017, 1,216 of them can be linked to traffic noise.
“I am surprised by the result because, for the first time, we can demonstrate a link between traffic noise and the development of dementia. Studies have been carried out previously, but they were smaller and not consistent” says Manuella Lech Cantuaria, PhD at the Maersk McKinney-Moller Institute and the Clinical Institute at SDU. She has led the extensive study.
The research project with health data from almost two million Danes was compared in terms of addresses and housing conditions in the period 2004 to 2017 and can thus, for the first time, document a link between traffic noise and the development of dementia.
The research is the largest of its kind in the world and demonstrates an increased risk of developing dementia, particularly Alzheimer’s disease, for people exposed to noise from roads and trains. Health data from all Danes over the age of 60 are compared was compared with population register information on their address and the traffic noise to which they were exposed.
Little research has been done on traffic noise and dementia, but the Danish results show that noise, like cardiovascular disease and poor lifestyle, also plays a major role in the development of dementia.
Major potential to prevent dementia
At Roskilde University, Mette Sørensen stresses that the results from the 3-year project could pave the way for even more, much-needed research in the field.
“Our result could potentially open up new possibilities for preventing dementia. If the conclusion is replicated in future studies, there is major potential for dementia prevention, as about 30% of all Danes are exposed to road noise that exceeds the Danish Environmental Protection Agency's limit of 58 decibels," she says.
This is an observational, database-based study that does not establish causality, but it does document a link that, according to the researchers, society needs to explore further in new research.
Possible explanations for a noise effect on health include the release of stress hormones and sleep disturbances leading to cardiovascular disease, changes in the immune system and inflammation – all of which are seen as early events in the onset of dementia and Alzheimer's disease.
“The next important step is to look more closely at what actually happens in the body when noise causes dementia. One possible explanation is that stress and poor sleep caused by noise can weaken the immune system, but more research is needed in this area," says Mette Sørensen.
For further information, contact:
- Adjunct Professor at the Department of Science and Environment, Roskilde University, e-mail: firstname.lastname@example.org, mobile: +45 30 23 68 03
- Press officer Camilla Buchardt, e-mail: email@example.com, mobile: +45 22 38 82 82
Facts about the study
Researchers from SDU, Roskilde University and the University of Copenhagen have spent three years studying the link between traffic noise and the risk of developing dementia. Similar studies have been conducted in the past, but access to the large Danish health registers has made it possible to conduct the largest international study in this field to date, with data from almost two million Danes over the age of 60 from 2004 to 2017.
The researchers have demonstrated a correlation by combining information and data on the participants’ address and thus their exposure to traffic noise over a 10-year period.
For example, the results show that people have a 27% increased risk of developing Alzheimer’s and an 18% increased risk of dementia from noise on the so-called quiet side of buildings when exposed to noise above 55 decibels for a number of years. There is generally an increased risk of 16% for noise above 65 decibels.
If we look at the number of dementia cases in 2017 in isolation and compare them with the results from the study, this means that of the 8,475 cases in 2017, 1,216 of them can be linked to traffic noise.
The researchers assessed road traffic and railway noise on the most and least exposed sides (or façades) of all residential addresses in Denmark.
They then analysed national health records to identify cases of dementia from all causes, and three different types of dementia (Alzheimer's disease, vascular dementia and Parkinson's disease-related dementia) over an average of 8.5 years.
They found 103,500 new cases of dementia during the study period.
Further analysis by type of dementia showed that both road traffic and rail noise were associated with a higher risk of Alzheimer’s disease, up to 27% higher for exposure to road traffic noise at 55 decibels and up to 24% higher for exposure to rail noise at 50 decibels compared to less than 40 decibels.