Living near a busy road has long been associated with health problems like heart disease and stroke. Now, a new study from Denmark suggests that chronic exposure to traffic noise may also increase the risk of developing Parkinson's disease, one of the most common neurodegenerative disorders worldwide.
Researchers from Aarhus University and other Danish institutions analyzed data from over 3 million Danes aged 40 and older, tracking them from 2000 to 2017. They found that for every increase of roughly 11 decibels (dB) in noise on the most exposed side of a home, the risk of Parkinson's rose by about 3%. On the quieter side of the house, each additional 9 dB of noise was linked to a 4% higher risk.
The study, published in JAMA Neurology, also highlighted a protective effect: homes where one side was at least 10 dB quieter than the other appeared to buffer residents from the worst effects. People without such a quiet side faced more persistent and unavoidable noise, especially at night, which the authors noted is particularly harmful.
Why Noise Matters for Brain Health
The researchers suggest that chronic noise disrupts sleep—a critical process for brain maintenance—and triggers systemic stress responses. These can lead to neuroinflammation and oxidative stress in brain regions responsible for dopamine production, the very areas affected in Parkinson's disease.
Parkinson's affects over 11 million people globally, and its prevalence is expected to more than double in coming decades as populations age. The exact cause remains unknown, and there is no cure. Identifying modifiable environmental risk factors is therefore a public health priority, said Fernando Alonso Frech, a neurologist at the HM CINAC Comprehensive Neuroscience Center in Madrid, who was not involved in the study.
“The large proportion of the population exposed to traffic noise means its potential impact on public health could be considerable,” Alonso Frech said. “These findings reinforce the importance of policies aimed at reducing urban noise pollution, through strategies such as urban planning, noise barriers, reducing traffic in residential areas, or designing housing with façades and resting spaces that are less exposed to noise.”
The results were consistent regardless of sex, education, income, cohabiting status, or population density. The authors note that previous studies focusing only on the loudest side of a house may have underestimated health risks by failing to account for whether residents had a quiet retreat.
While the study does not prove causation, its scale and biological plausibility add weight to calls for stricter noise regulations in European cities. From Copenhagen to Milan, urban planners are already grappling with the health impacts of traffic, and this research provides another reason to prioritize quieter streets and better-insulated homes.
For those living in noisy areas, the findings suggest that even a small reduction in noise exposure—such as moving a bedroom to the quieter side of the house—could have meaningful benefits. As Europe's population ages and Parkinson's cases rise, such simple interventions may become increasingly important.
