Exposure to Air Pollution Linked to Increased Risk of Parkinson’s Disease

Increased exposure to air pollution in the form of particulate matter with a diameter of 2.5 µm or less (PM_2.5) and nitrogen dioxide (NO₂) was associated with a higher risk for Parkinson’s disease, according to a population-based case-control study in JAMA Network Open.

In this video interview, Brittany Krzyzanowski, PhD, of Barrow Neurological Institute in Phoenix, and Rodolfo Savica, MD, PhD, of the Mayo Clinic in Rochester, Minnesota, discuss the results of their study.

The following is a transcript of their remarks:

Krzyzanowski: So, in this study, we wanted to test the association between air pollution and Parkinson’s disease risk, also the clinical phenotypes and whether air pollution increases the risk of more severe Parkinson’s symptoms, specifically dyskinesia.

We used a population-based dataset of more than 6,000 people. This included more than 400 patients with Parkinson’s disease and their address history spread across the Midwest. So we were able to link patients to their air pollution exposures and test the impact of the two types of air pollution in the study, which would be particulate matter and nitrogen dioxide. We were looking at these two types of air pollution and their impact on Parkinson’s disease.

What we found was an association between air pollution and the risk of Parkinson’s disease, specifically in people living in neighborhoods with the highest levels of air pollution. These people had increased risk of developing the akinetic rigid form of the disease, as well as dyskinesia, compared to those who were exposed to lower levels of air pollution in our study region.

We found that the association between air pollution and Parkinson’s disease was stronger in metropolitan areas in our study area — the metros — and this aligns with the fact that we also detected the relationship between Parkinson’s and nitrogen dioxide exposure. So these two findings together suggest that there’s a possibility that the PM_2.5 association … may be driven in part by the traffic-related particulates.

Savica: The importance of this study and the results are pointing to a very interesting aspect.

The fact that in Parkinson’s disease — which as you all know is a degeneration of the brain, for the most part — the drive of degeneration is indeed potentially initiated and enhanced and perpetuated by environmental factors, in this case that would be the air pollution, that not only increases the risk overall, but also modifies some of the characteristics of the disease.

In this case, we are seeing a stronger association with a particular type of Parkinson’s that is called akinetic rigid. Usually people that have this particular type are slower, they’re falling, they’re more rigid, they’re more stiff, they don’t have too much tremor.

And the association that was incredibly relevant from a clinical standpoint was that one of the most feared complications of the treatment of Parkinson’s disease is the presence of dyskinesia — those are involuntary movements that come after years of treatment with the right medication — and that is the most feared within our population of patients. Well, the fact that an environmental factor, in this case air pollution, can modify the characteristic of the disease leading to an increased risk of having dyskinesia — it’s a first.

The Rochester Epidemiology Project is a project that is unique in its genera and allows us to do this study. In other datasets, despite maybe being larger, we would not be able to tell the granularity of the information that we have now in this cohort that would provide us information, not only about the disease, but also the confirmation of the real diagnosis, the confirmation of the symptoms, and the presence and timing of the symptoms through our lifetime, because, for most of the people that are involved in this project, we do have information from the moment they were born to the moment they actually passed, which is unique and allows us to do this study, obtaining very informative results in a very short term.

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