Air pollution exposure tied to higher Parkinson’s risks, study finds

More exposure to air pollution over the years could increase people’s risk of developing Parkinson’s disease later on, a new study suggests.

For years, researchers have been exploring potential links between air pollution and the incurable degenerative disease, where nerve cells deteriorate in the part of the brain that controls movement, causing slurred speech, tremors, and stiffness.

Scientists believe that Parkinson’s is caused by a combination of genetic and environmental factors.

One potential culprit is PM2.5 – fine particulate matter that can travel far distances – because it can cross the blood-brain barrier, causing inflammation and oxidative stress and prompting the brain’s immune cells to activate so they can destroy pathogens.

These factors could enable Parkinson’s to develop and progress, according to researchers from the Barrow Neurological Institute and Mayo Clinic in the United States.

Their new study, published in the journal JAMA Network Open, suggests that the amount of air pollution someone experiences over time is also an important piece of the puzzle – and that curbing exposure could lower Parkinson’s risks and change how the disease develops.

Reducing air pollution could “not only [prevent the] development of Parkinson’s disease but also [improve] the quality of life of patients that [already have it],” Dr Rodolfo Savica, the study’s senior author and a neurologist at Mayo Clinic, told Euronews Health.

The study included nearly 5,200 people, including about 350 with Parkinson’s, and tracked their pollution exposure levels from 1998 to 2019.

Researchers found that people were more likely to have Parkinson’s if they had higher levels of exposure to PM2.5 and nitrogen dioxide – which mainly comes from cars, power plants, or other fuel emissions – in the 10 years before their diagnoses.

In metropolitan areas, people living in neighbourhoods with the highest levels of air pollution were 23 per cent more likely to develop Parkinson’s compared with people in areas with the lowest levels, Savica said.

Meanwhile, Parkinson’s patients with higher PM2.5 exposure levels were more likely to develop dyskinesia – muscle spasms in the face, arms, legs, or torso – and to present with akinetic rigidity – the stiffness and tremors that are characteristic of the disease – compared with those who were exposed to lower pollution levels over the years.

“Although we cannot make causal conclusions, the implications are such that moving from neighbourhoods with high PM2.5 could lower someone’s risk of developing Parkinson’s disease and complications of Parkinson’s disease,” Savica said.

Parkinson’s disease growing

Notably, higher PM2.5 exposure was not tied to a greater likelihood of death for Parkinson’s patients, though researchers said that the people in the study may have had better access to medical care than the average patient.

Previous research spanning six European countries found that long-term exposure to PM2.5, even at levels far below the European Union’s air pollution limits, could contribute to Parkinson’s deaths.

Parkinson’s disease affects an estimated 10 million people globally, and the number is growing in countries with ageing populations.

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In the EU, there were 344 Parkinson’s patients per 100,000 people in 2021, up from 224 in 2000, according to global disease burden estimates.

For the latest report, the authors said that the study’s geographical focus, lack of patient diversity, and other unknown variables, such as whether people spent more time away from home than expected, could have skewed the results.

Savica said the next steps for this research are to explore how other types of air pollution could affect Parkinson’s risks, and to better understand the link between genetic and environmental factors.