Long-term exposure to a busy road may increase the chances of developing Parkinson's disease, though a quiet side of the house could give some protection, new research suggests.
Long-term exposure to road traffic noise was associated with a higher risk of Parkinson’s disease, possibly due to sleep disruption and systemic stress, according to a new study.
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Danish researchers analysed over three million residents to determine if persistent noise in different residential areas and positions increases the risk of this neurodegenerative disorder.
The study, published in the journal JAMA Neurology, looked at over three million Danes between 2000 and 2017 who were at least 40 years old and free of Parkinson’s disease at the start of the study.
For every rise of roughly 11 decibels (dB) in noise on the most exposed side of a home, the risk of Parkinson’s disease increased by about 3%, the researchers found.
On the quiet side of the home, the one least exposed to traffic, the Parkinson’s disease risk rose by 4% for every additional 9 dB of noise.
At the same time, the study found that a quiet side — where one side of the house is at least 10 dB quieter than the other — acts as a protective buffer which can mitigate these harmful effects, particularly for those living with higher overall noise levels.
People without a quiet side face a more persistent and unavoidable level of noise, especially at night, which the authors noted is more harmful.
The study’s authors added that previous studies only looking at the loudest side of a house might underestimate the health risks, because they fail to account for whether residents have a quiet place to retreat to.
The results were consistent regardless of sex, education, income, cohabiting status and population density.
How does noise affect Parkinson’s disease risk?
The authors suggest that these findings are biologically plausible because chronic noise can disrupt sleep, which is vital for brain health, and can also trigger a stress response in the body.
It can also cause "neuroinflammation" and oxidative stress in the brain, specifically in areas related to dopamine production.
Parkinson’s disease is the second most common neurodegenerative disorder worldwide, affecting over 11 million people according to recent research, a burden expected to more than double in the coming decades as people live longer and some countries experience population growth.
In Parkinson's disease, nerve cells in the brain called neurons slowly break down or die. Many symptoms are caused by a loss of dopamine-producing neurons, resulting in irregular brain activity.
The exact cause of the condition is unknown, and there is currently no cure.
“Therefore, identifying potentially modifiable environmental factors is a public health priority,” said Fernando Alonso Frech, neurologist and researcher at the HM CINAC Comprehensive Neuroscience Center, who did not participate in the study.
He added that the large proportion of the population exposed to traffic noise means its potential impact on public health could be considerable.
“In this context, the findings reinforce the importance of policies aimed at reducing urban noise pollution, through strategies such as urban planning, the creation of noise barriers, reducing traffic in residential areas, or designing housing with façades and resting spaces that are less exposed to noise.”
