Parkinson’s disease (PD) impacts millions of people all over the globe—but knowing just how many people have the disease remains a big challenge. There are no universal reporting requirements for PD, either in the United States or the international community, meaning scientists need to put significant resources into estimating the number of cases. That’s partially why a study published in The BMJ in March 2025 estimating the number of Parkinson’s cases will grow to more than 25 million by 2050 has created conversation.
After all, this prediction would represent a 112% increase from 2021.
The study points to an aging global population as the primary driver of the growth in cases, and the authors note that the rise represents a growing public health challenge.
These numbers are just estimates, though. Brian Fiske, PhD, chief science officer at
The Michael J. Fox Foundation, points out, “There are important unknowns that prevent a pinpoint calculation. We have imperfect measurements and so we are often stuck with imperfect estimates.”
For example, researchers predict prevalence (the total number of cases) is based, in part, on incidence (how often new cases develop). However, there are reasons to believe the incidence rate could also fluctuate. Banning dangerous chemicals, for example, could reduce the incidence rate, while permitting their use could increase it — as certain chemicals are known to contribute to Parkinson’s. A change in either direction would affect the estimate of total number of cases by a given year. This is compounded by a number of other factors that influence prevalence figures, such as underdiagnosis in communities where there is a strong stigma surrounding PD or evolving disease definitions based on new biological discoveries.
Fiske notes, “Very smart people are doing the work to get as close as possible on these estimates. Understanding how many people there are with PD out there in the world goes such a long way towards demonstrating the importance of Parkinson’s research.”
MJFF continues its own work determining the impact of Parkinson’s, ranging from efforts to facilitate state governments creating registries to track cases to partnerships across the field to determine economic burden.
The estimate from this study — 25 million people with PD by 2050 — contributes to a broader picture of Parkinson’s disease, and while it may not be able to fully pinpoint the growth of PD, it certainly points to the importance of efforts towards a cure.