AAN 2026 | Environmental risk and rising incidence of Parkinson’s disease: insights from population data

Parkinson’s disease is a disease that we’ve seen in the last few decades as an increasing disease. It means that there’s a number of new cases. Incidence is spiking, prevalence is increasing, so we know that there’s a number of total new cases that every year keep on increasing in every nation, not necessarily in the developing countries, but we see globally a constant increase of this condition. So the reason why this increase is happening is a little bit unclear. A number of ideas have been thrown, such as, for example, more diagnostic abilities, at least to identify patients earlier, but in reality, we don’t have a good explanation. We know that together with this increase of the disease, we have seen a number of different environmental exposures that have been on the rise. Through the years, pesticides, for example, have been associated with an increased risk of developing the disease. And with our study that we conducted in Minnesota, in Olmsted County, Minnesota, and the surrounding counties, we were basically looking at the exposure to golf courses indirectly in the means that water, wells, water contamination, pesticide use used around the golf courses, if they were changing the frequency of Parkinson’s disease in this population that lives nearby the golf courses. Well, we found that. We saw that basically people that were living in the vicinity within one to three miles, to six kilometers from the golf courses in the radius, they were having a 126 percent increased risk of Parkinson’s disease, and this risk was slightly lower, was reduced if the people that were living around the golf courses were using private well water. The idea was indeed that this contamination coming from the golf courses has to do with water, with water that we are consuming in our households, the water we are exposed to, obviously, also oxygen, obviously we have to breathe, so the air that we breathe is also having a major role, but that is a bit more difficult to identify just because we are needing to breathe oxygen every moment of our life. The key point of this is that we noticed that if we were living within a mile, three months from golf courses, the risk was way increased. And as we were moving away from the golf courses, there was a dose-dependent decrease of the risk of Parkinson’s disease. This is shedding light on the idea that the environment plays a role in the development of Parkinson’s disease. And we know it’s the case. But I want to be not that simplistic. Not everyone that lives in the golf course area or next to a big factory would have Parkinson’s. There’s an individual predisposition, genetic predisposition, to develop the disease. So you need to have both. Let me pass the term. You have to have two hits. Individual predisposition and environmental factors acting together. Some patients have more individual predisposition, genetic mutation. Some others have more environmental factors. But clearly, it’s not just the environment. It’s not just the genetics. It’s these two and maybe more. Maybe more things that are affecting ourselves during our lifetime. Because we are talking about an exposure that is lifelong. It’s not an exposure that is just discrete, a toxic environmental agent once. No, it’s done through a number of years and I’m expecting and we know that we’ve been exposed to environmental agents the moment that we were born, actually even before we were in the womb, within our own mothers, our mothers were exposed to water, to oxygen, and we are vicariously being fed by these particulars, not nutrients. So clearly, we have been exposed for our life and that’s a major role to consider. That’s why it’s not easy sometimes to identify these particular environmental agents. But the lack of our area is that we have this fantastic, powerful tool called the Rochester Epidemiology Project, a project that spans around the Mayo Clinic, but not only, where everyone that was ever seen in the hospital, in any of the hospitals surrounding the areas, had been assigned a number, a record linkage number. So we may have data from the moment that people were born, the moment people died, so 60, 70, 80 years of exposure to medical needs, obviously people can move, can get in, but those are all considerations that we have. This provides us the uniqueness of our area, which is to have very detailed, granular information on the way they live, or what people do, or where they live, or obviously medical information, but also work information, environmental exposure, something that can be happening only when you have this very clear and granular group of information that has been collected through the last 60 years, I would say.

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