Noise is an important health hazard
Traffic noise is one of the most important environmental factors hazardous to health. Scientists believe that in Europe, only air pollution is causing more damage. More than a quarter of the European population is exposed to noise levels above the maximum recommended loudness of 55 decibels.
Studies have linked exposure to traffic noise to the risk of various diseases, including coronary heart disease, obesity, and diabetes. Scientists speculate that noise can trigger the release of stress hormones that affect various bodily functions.
Noise at night leads to poor sleep quality. In experiments, it has been associated with vascular dysfunction, increased oxidative stress, endocrine system problems, and systemic inflammation. All of these factors are associated with the risk of developing dementia, in particular, Alzheimer’s disease.
Many of the previous studies on the association of noise with dementia risk were of low quality. Therefore, scientists from Denmark decided to clarify how serious this connection is.
What the new study showed
The authors of a new study, published in The BMJ, analyzed the link between long-term exposure to traffic noise and the risk of dementia using the example of two million people over the age of 60 who lived in Denmark from 2004 to 2017. They assessed the level of traffic and train noise in the areas where the people included in the study lived. Next, they checked how often they developed dementia over the course of 8.5 years.
Scientists compared how often dementia develops in people who are exposed to the highest and lowest (less than 40 decibels) noise levels.
It turned out that the ten-year risk of developing Alzheimer’s disease was 27% higher with traffic noise of 55 decibels and 24% higher with noise of 50 decibels. Only traffic noise was associated with an increased likelihood of developing vascular dementia, not trains.
When calculating, the scientists took into account the presence of other factors that can affect the risk of developing dementia in the study participants. As an observational study, the findings do not prove that noise increased the respondents’ risk of dementia – such studies may still miss some important factors. However, the strengths of the work were the large sample size and long observation period.
Scientists believe that if future research confirms the described effect of noise, control of it has the potential to be an important part of dementia prevention.