according to new research that investigators say highlights the growing strain on clinical services and the need for more research funding.
In an analysis of five databases and more than 15 million people, about 60,000-90,000 individuals older than 45 years are estimated to be diagnosed with Parkinson’s disease each year – which is far more than the previous estimate of around 40,000-60,000 new cases annually.
This is the latest study to update decades-old epidemiologic data on Parkinson’s disease incidence and prevalence. Previous incidence rates came from small, single-population studies that are now more than 25 years old.
“In the advocacy community, we’ve been earnest about the impact of people living with Parkinson’s disease, and what we really lacked was sufficient data to be able to demonstrate the urgency of our need,” said study coinvestigator James Beck, PhD, chief scientific officer at the Parkinson’s Foundation, New York.
“We wanted to revise these numbers, highlight that they are larger than people anticipated, and use it as a call to action to change the approach we have toward Parkinson’s,” Dr. Beck said.
The findings were published online in NPJ Parkinson’s Disease.
Updating an outdated model
The study builds on the Parkinson’s Prevalence Project, a 2018 initiative that used a new model to calculate Parkinson’s disease prevalence. Before then, federal prevalence data was based on a 40-year-old study of just 26 Parkinson’s disease cases in one small county in rural Mississippi.
Dr. Beck and others used a more sophisticated model, using data from five separate cohort studies. They estimated the total number of patients living with Parkinson’s disease in the United States to be 930,000, which is far higher than the 650,000 the old model predicted.
Researchers then moved on to the current project, developing a new method to estimate Parkinson’s disease incidence.
The project included 2012 data on more than 15 million individuals in the United States and Canada. The investigators drew from three large insurance databases (Kaiser Permanente Northern California, Ontario Health Care, and Medicare) and two long-term epidemiologic studies (the Honolulu-Asia Aging Study and the Rochester Epidemiology Project).
On the basis of their analysis, the investigators proposed a working Parkinson’s disease incident rate estimate of 47-77 cases per 100,000 people aged 45 years or older. Limiting the analysis to those aged 65 or older raised the incidence to 108-212 per 100,000 people.
That translates to 60,000-95,000 new cases each year among adults aged 45 years or older. Using the Medicare administrative database alone for this same time period suggests an annual incidence of nearly 90,000 for individuals aged 65 or older.
“The numbers we’re proposing are conservative,” Dr. Beck said. “The true numbers are probably north of 90,000.”
Incidence rates increased with age and were higher in men. The researchers also identified clusters of counties with higher incidence rates in parts of the country called the “Parkinson’s belt.”
That geographic area mirrors the Rust Belt and includes parts of the Northeastern and Midwestern United States with a long history of industrial manufacturing that used heavy metals and industrial solvents, which are environmental factors linked to risk for Parkinson’s disease.
Cases were also higher in southern California, southeastern Texas, and Florida – agricultural regions with high pesticide use, which is also a risk factor for Parkinson’s disease. Central Pennsylvania also had higher incidence rates.