Study: traffic noise could increase the risk of Parkinson's disease

Prolonged exposure to road traffic noise could increase the risk of developing Parkinson's disease, according to a new study published in the journal JAMA Neurology, as cited by Euronews. The researchers believe that disrupted sleep and chronic stress caused by intense noise could contribute to the onset of this neurodegenerative disease.

Danish researchers analysed data from more than three million residents of Denmark, collected between 2000 and 2017. Participants were at least 40 years old and had not been diagnosed with Parkinson's disease at the start of the study. The aim was to determine whether persistent noise in residential areas, as well as the position of a dwelling relative to the noise source, influences the risk of developing the disease.

The results show that for every increase of approximately 11 decibels in noise on the most exposed side of a home, the risk of developing Parkinson's disease rises by around 3%. On the quieter side of the home, the risk increases by 4% for every additional 9 decibels.

The study also found that having a quiet side to one's home — at least 10 decibels quieter than the other side — acts as a protective buffer, reducing the negative effects of noise, particularly for residents exposed to generally high levels of noise pollution. By contrast, people whose homes have no quiet area experience noise more constantly and inevitably, especially at night, which the study's authors consider more harmful.

The researchers caution that previous studies, which only took into account the noisiest side of a dwelling, may have underestimated the true health risks, as they did not consider whether residents had access to a quieter space in which to retreat.

The findings remained consistent regardless of sex, education level, income, cohabitation status, or population density in the area.

How noise could affect the brain

According to the authors, these findings are biologically plausible: chronic noise can disrupt sleep, which is essential for brain health, and can trigger a stress response in the body. It may also cause neuroinflammation and oxidative stress in the brain, particularly in areas involved in dopamine production.

Parkinson's disease is the second most common neurodegenerative disease worldwide, affecting more than 11 million people, according to recent research. The number of cases is estimated to double in the coming decades as life expectancy increases and populations age in certain countries.

In this disease, neurons in the brain gradually deteriorate or die. Many of the symptoms are caused by the loss of dopamine-producing cells, which leads to irregular brain activity. The exact cause of the disease remains unknown, and there is currently no cure.

Fernando Alonso Frech, a neurologist and researcher at the HM CINAC Integrated Neurosciences Centre, who did not participate in the study, stated: "Identifying potentially modifiable environmental factors is a public health priority." He added that, given the large proportion of the population exposed to traffic noise, its impact on public health could be considerable.

"The study's findings highlight the importance of policies aimed at reducing urban noise pollution, through strategies such as urban planning, the construction of noise barriers, reducing traffic in residential areas, or designing homes with façades and rest areas that are less exposed to noise," the specialist added.