Dr Ray DorseyE. Ray Dorsey, MD
Studies have shown that from 1990 to 2015, the number of people with Parkinson disease in has doubled to more than 6 million, and a recent projection has suggested that both the United States and the world are on the brink of an emerging Parkinson disease pandemic.1

Additionally, while this projection was focused on Parkinson prevalence as a disease, the authors noted that the total burden caused by additional parkinsonian disorders, such as vascular parkinsonism or neurodegenerative atypical parkinsonism, is even greater.

To find out more about the study’s findings, NeurologyLive spoke with lead author E. Ray Dorsey, MD, the David M. Levy Professor of Neurology and director of the Center for Health and Technology at the University of Rochester Medical Center, in an interview. Dorsey also discussed his and his colleagues’ ideas for how to address this impending—but not inevitable—pandemic.

NeurologyLive: What prompted this research into the projection of Parkinson disease prevalence?

E. Ray Dorsey, MD: We've been looking at this issue for over a decade. We wrote a paper in Neurology in 2007 on the projected number of people with Parkinson disease in the world's most populous countries, and we projected then that it would double. Then, the Global Burden of Neurological Disease study came out about a year or so ago and that highlighted that neurological disorders are now the leading source of disability in the world. The fastest growing of those disorders is Parkinson disease.

A colleague of mine, Alexis Elbaz, MD, PhD, from France, and I helped lead the Global Burden of Parkinson disease study, in which we detailed that Parkinson is increasing in every region in the world. The areas where it's increasing the fastest are China—where age-adjusted rates have more than doubled—and the US. Globally, theage-adjustedd rates for disability, death, and the number of people affected have all increased by about 20%.

If you take those projections because the populations are aging and because Parkinson disease is associated with many products and byproducts of industrialization, the number of people with Parkinson will double again in the coming 25 years. When you start to see that something doubles every 25 years, that’s an exponential rise, and it's affecting the whole world. There aren't any areas of the world where Parkinson isn't increasing. It makes you think that we're in the midst of a pandemic, not of an infectious disease, but a pandemic of a chronic condition, and a pandemic that could be facilitated by the increased use of things that have been linked to Parkinson disease, such as pesticides and solvents.

What’s been the projection for this in the United States?

The global burden of disease study estimated that the number of people with Parkinson disease was around 700,000 in the United States. A paper by Connie Maris, Carly Tanner, and colleagues gave a minimum estimate of the number of people with Parkinson disease in the US in 2020. They said the overall prevalence in the US will rise to approximately 930,000 in 2020, and that these estimates should be considered minimum estimates.

The Global Burden of Disease study estimated that the number of people with Parkinson disease in the US was 700,000 in 2016. China was the most, the US is second. And almost every study that's done only raises estimates and the great study that was published maybe about 10 years ago and says that the higher the quality of the estimate, the higher the value becomes, so we're only underestimating.

What needs to be done to start addressing this pandemic?

There are 4 things we can do. We can one, prevent it. It's clear that there are modifiable risk factors for Parkinson, chief among them is the use of pesticides. One pesticide that's used commonly that's been banned by 32 countries and been linked to Parkinson's disease is paraquat. That’s been banned by 32 countries including China but is still used in the US. England banned it but exports it to the US, Indonesia, and Brazil and other countries. The EPA has proposed banning it but recently indicated that they were going to indefinitely postpone action on it. Other pesticides have been linked or classes that belong to organochlorine pesticides, including DDT—many of those have been banned in the US but not in other parts of the world. A chemical called trichloroethylene, which is used as a spot remover in dry cleaning and as a degreasing agent, has also been proposed to be banned by the EPA, but the EPA has yet to take action to my knowledge. It's the most common contaminant of groundwater in the US, and affects about a half of the Superfund sites throughout the country. Head trauma is also associated with Parkinson disease, other studies have linked individual habits, such as drinking caffeine and vigorous exercise to a decreased risk of Parkinson disease.

The second is the advocacy front. Despite the fact that Parkinson is increasing in its burden, the NIH funding, adjusted for inflation, for Parkinson disease is decreasing. Things have changed. The diseases where we've made the greatest progress over the last 25 years or so, like in HIV, where there was broad societal engagement by those with and those without the disease. Given that our lifetime risk of—yours and mine—developing Parkinson disease is on the order of 1 in 15, we should all be doing more to develop and secure more resources for Parkinson disease.

On the care front, over 40% of Medicare beneficiaries, so about 40% of people with Parkinson in the US don't see a neurologist. Those that don't have worse health outcomes including higher rates of fracturing their hips, higher rates of being placed in a skilled nursing facility, and higher rates of death. We need to find new care models that increase access to care for people with Parkinson disease, and focus on bringing care to patients instead of patients to care.

Then, on the treatment front for Parkinson, the most effective treatment is levodopa, which is more than 50 years old. There are few medical conditions in the US where the most effective treatment is 50 years old. In this century, we've had only 2 new classes of drugs approved for Parkinson disease—1 for lightheadedness and 1 for psychosis, which affect a subset of people with Parkinson disease. It's clear that we need to develop more effective treatments and develop better measures to determine whether the new drugs work or don't work because currently, our measures have significant limitations and are very subjective.

We put all that under the umbrella of a PACT. What can we do to Prevent the disease, what can we do to Advocate for additional resources, what can we do to Care, and what can we do to Treat.

What’s the one thing you want clinicians to take away from this?

Parkinson disease is becoming more common, and if we don't act it is only going to become more common. Their risk of developing Parkinson is 1 and 15, so if they're concerned in their self-interest, they should be very motivated to think about the ways that we can prevent this disease from occurring. Then, obviously, as clinicians, what can we do to improve care by bringing care to patients instead of bringing patients to care for people with Parkinson disease. It’s the fastest growing neurological disorder, and we should do something about it.
REFERENCE
1. Dorsey ER, Sherer T, Okun MS, Bloem BR. The emerging evidence of the Parkinson pandemic. J Parkinson Dis. 2018;8(Suppl. 1): S3-S8.
doi: 10.3233/JPD-181474.