People exposed to road traffic noise for many years may face a higher risk of developing Parkinson’s disease, according to the largest study ever conducted on the subject. Researchers say constant noise exposure could affect brain health by causing long‑term stress and disrupting sleep.
The study, published in JAMA Neurology, followed 3.1 million adults aged 40 and above in Denmark over 18 years. Using national health records and residential data, researchers examined how long‑term exposure to traffic noise influenced the likelihood of developing Parkinson’s disease.
Findings showed that for every 11.5‑decibel increase in road traffic noise outside a person’s home, the risk of developing Parkinson’s disease rose by 3 per cent. While the increase may appear small, researchers said the link remained consistent throughout the study, suggesting long‑term exposure to traffic noise could play a role in the disease’s development.
Researchers also found that people with a quieter side of their homes appeared to have a lower risk of developing Parkinson’s disease. This suggests that reducing noise exposure, particularly during sleep, may help lessen harmful effects associated with long‑term traffic noise.
Parkinson’s disease is a progressive neurological disorder that develops when nerve cells in the brain responsible for producing dopamine become damaged or die. The disease mainly affects movement, causing symptoms such as shaking, stiffness, slowed movement, and poor balance. As the condition progresses, many patients also experience difficulties with speech, swallowing, memory, and other daily activities.
Although the exact cause of Parkinson’s disease remains unknown, scientists believe it results from a combination of genetic and environmental factors. Previous studies have linked the condition to exposures such as pesticides, air pollution, and certain industrial chemicals. The new research adds road traffic noise to the growing list of environmental factors that may contribute to the disease.
According to researchers, one possible explanation is that continuous exposure to traffic noise triggers chronic stress. Persistent noise can increase production of cortisol, commonly known as the stress hormone. High levels of cortisol over time have been associated with inflammation and damage to brain cells.
Researchers also noted that road traffic noise frequently interrupts sleep. Poor‑quality sleep has increasingly been recognised as an important factor affecting brain health. Sleep allows the brain to repair itself and remove waste products that build up during the day. When sleep is repeatedly disturbed, these natural repair processes may become less effective, increasing the risk of neurological disorders over time.
The study accounted for other environmental factors, including air pollution, to ensure the observed relationship was not explained by pollution alone. The association between road traffic noise and Parkinson’s disease remained even after adjusting for these factors.
However, researchers acknowledged they did not have detailed information on participants’ lifestyles, including smoking, diet, and physical activity, which may also influence risk. Despite this limitation, they found similar results regardless of participants’ income or education levels.
Researchers said the findings strengthen evidence that environmental noise should be considered a potential risk factor for Parkinson’s disease and warrant further investigation. "The findings move road traffic noise from being a possible risk factor to one that deserves serious attention and further research."
Independent experts welcomed the findings but urged caution in interpreting the results. They noted the study shows an association between traffic noise and Parkinson’s disease but does not prove noise directly causes the condition.
They explained that people living near busy roads may also be exposed to other environmental and social factors that could contribute to the disease. More research will therefore be needed to determine whether traffic noise itself is responsible for the increased risk.
According to the World Health Organisation (WHO), chronic noise exposure above recommended levels affects nearly one‑third of people in Europe, mainly due to road traffic. It notes that the number of people living with Parkinson’s has more than doubled over the past 25 years due to population growth and ageing.
Researchers project the number could rise to 25.2 million by 2050 if current trends continue.
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