• Transportation noise is an environmental risk factor for public health in Europe
  • Researchers found association between transportation noise and all-cause dementia
  • Knowing more about noises' harmful effects may help inform prevention efforts

Exposure to traffic noise for a long period of time may increase the risk of developing dementia, particularly Alzheimer's disease, researchers of a new study found.

Noise from transportation is considered to be the "second worst environmental risk factor" when it comes to public health in Europe, following air pollution, the British Medical Journal (BMJ) said in a news release. A fifth of people is said to be exposed to transportation noise that’s above the recommended 55 decibels (dB).

The researchers of the new study, published in The BMJ today, noted that 55 dB is about the same as the noise in an open office environment.

This is problematic because exposure to traffic noise isn't just bothersome and annoying, it has been linked to certain health problems such as diabetes, obesity and coronary heart disease.

"A few studies have, however, suggested that transportation noise might lead to cognitive impairment in adults," the researchers wrote. "Therefore, further high-quality population-based studies are required to test the hypothesis of a potential association between exposure to transportation noise and risk of dementia."

Dementia is among "the greatest health challenge of the 21st century," the researchers said. By the year 2050, the number of people with dementia worldwide is expected to reach more than 130 million. According to the BMJ, this is a "costly and growing global health crisis."

To shed light on the transportation noise's association with dementia risk, the researchers had a closer look at data from about two million adults over 60 years old in Denmark from 2004 to 2017.

For the study, the researchers estimated the road traffic and railway noise in the most and least exposed residential areas in Denmark. They also looked at the cases of all-cause dementia and its types in national health registers and found 103,500 new cases during their study period.

"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," the researchers wrote.

In 2017, for instance, they found that about 1,216 of the 8,475 cases of dementia in Denmark may be "attributed" to noise exposure. What's more, looking further into the types of dementia, they found the "highest and most consistent" risk estimates for Alzheimer's.

The study found a 27% higher risk of Alzheimer's disease from exposure to traffic noise over 55 dB and a 24% increase from exposure to railway noise over 50 dB. When it came to vascular dementia, however, the increased risk was only associated with traffic noise, but not railway noise, the BMJ noted.

The findings run similar to that of a study in 2020, wherein researchers found those who were living with an added 10 dB in their residences had 30% higher odds of having Alzheimer's disease.

"If these findings are confirmed in future studies, they might have a large effect on the estimation of the burden of disease and healthcare costs attributed to transportation noise," the researchers of the current study wrote. "Expanding our knowledge on the harmful effects of noise on health is essential for setting priorities and implementing effective policies and public health strategies focused on the prevention and control of diseases, including dementia," the research stated.

Traffic Road Street Residential Area Representation. Photo: S. Hermann & F. Richter/Pixabay