Annual US Parkinson’s Rate 50% Higher Than Earlier Estimates

The number of US patients diagnosed with Parkinson’s disease (PD) each year is about 50% higher than previously thought, 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 PD 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 PD incidence and prevalence. Previous incidence rates came from small, single-population studies that are now more than 25 years old.

James Beck, PhD

“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,” study co-investigator James Beck, PhD, chief scientific officer at the Parkinson’s Foundation, New York City, told Medscape Medical News.

“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,” Beck said.

The findings were published online December 15 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Updating an Outdated Model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 PD prevalence. Before then, federal prevalence data was based on a 40-year-old study of just 26 PD cases in one small county in rural Mississippi.

Beck and others used a more sophisticated model, using data from five separate cohort studies. They estimated the total number of patients living with PD 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 PD incidence.

The project included 2012 data on more than 15 million individuals in the US 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 PD 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,” 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 US with a long history of industrial manufacturing that used heavy metals and industrial solvents, which are environmental factors linked to risk for PD.

Cases were also higher in southern California, southeastern Texas, and Florida — agricultural regions with high pesticide use, which is also a risk factor for PD. Central Pennsylvania also had higher incidence rates.

Why the Increase?

The increase in cases could be the result of the more comprehensive estimation model used, the researchers note. Or it could be improved detection, the aging population, a rise in sedentary lifestyles, increased exposure to environmental risk factors, or even the sharp decline in smoking in the US, as some studies have shown that smokers have a lower PD risk.

“The short answer is, we don’t know; and the long answer is, it’s all the above,” Beck said.

Although about 15% of PD cases have a genetic basis, the cause is unknown in the majority of cases. In addition, diagnosis is difficult because there is no blood test or scan that detects the disease.

“Diagnosis requires a skilled clinician with real familiarity with Parkinson’s. And we have a real shortage of neurologists in this country to not only be able to diagnose but also to treat the condition,” Beck said.

That was one motivation for doing the study: to highlight what experts say is a pending clinical crisis for patients with PD, he added.

The investigators also wanted to raise awareness about the scope of the disorder — not just about prevalence and incidence but also what those data mean for the healthcare industry, research aims, drug development and healthcare coverage, and policies.

In a 2020 study, the same researchers calculated a cost of $52 billion per year for medical and nonmedical costs related to PD, which works out to about $26,000 per year per patient. That figure is expected to surpass $79 billion by 2030.

“This is an urgent condition for many people who live with the disease. And to the extent we can get our country to recognize that and really make the investment now, this is an area where a stitch in time saves nine,” Beck said.

“If we can invest some money now, we have a chance to really make a difference in the future,” he added.

‘Groundbreaking’ Findings

Commenting for Medscape Medical News, Jori Fleisher, MD, MSCE, associate professor of neurological sciences at Rush University Medical Center in Chicago, called the results “groundbreaking” and said that they validate what clinicians have been seeing in real-world practice.

“The findings reflect what a lot of us in practice have been appreciating anecdotally, which is that it seems that Parkinson’s is being diagnosed more frequently and that the incidence has been rising,” said Fleisher, who was not involved with the study.

She noted that the use of multiple datasets is one element of the methodology that makes the data so significant.

“There has been great work out of individual centers; but no matter how good your study methods are within that one population, you’re drawing conclusions based on that one population,” Fleisher said.

This research, together with the previous work by the group on prevalence data, could go a long way toward raising awareness about the scope of PD in the US — which could lead to earlier diagnosis, more research funding, and increased attention on the need for more clinicians who specialize in movement disorders, she added.

“This should increase research funding across the spectrum, including everything from the basic science to translational research, clinical research and implementation, and health services research,” Fleisher said.

The study was supported by the Parkinson’s Foundation, The Michael J. Fox Foundation for Parkinson’s Research, and the Institute for Clinical Evaluative Sciences. Beck and Fleisher report no relevant financial relationships.

npj Parkinsons Dis. Published online December 15, 2022. Full article

Kelli Whitlock Burton is a reporter for Medscape Medical News covering neurology and psychiatry.

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