Parkinson Disease Incidence Substantially Greater Than Previously Reported, Study Shows

Incidence of Parkinson disease (PD) was shown to be 50% higher than previous estimates, and it increased with age and was greater among males. Findings were reported recently in npj Parkinson’s Disease.

PD is the second most common age-related neurodegenerative condition diagnosed in North America, with prevalence increasing at a faster rate than any other neurodegenerative disease.

As the population in Western nations has shifted to include a greater proportion of older adults, the public health and economic burdens of age-associated neurodegenerative disease have increased as well, with an estimated economic cost of $52 billion per year in the United States alone, noted researchers.

Estimates of PD burden are vital to public health response efforts, and findings of a previous analysis by the study authors using multinational data from current and past epidemiology projects indicated that the prevalence of PD diagnoses was greater than previously reported.

Building upon their efforts for improved estimates of PD prevalence, they sought to investigate if this trend would also be true for PD incidence, an important complementary statistic that is a more direct reflection of the impact of risk factors for a disease.

“Prior PD incidence estimates have varied, for unclear reasons. There is a need for improved estimates of PD incidence, not only for care delivery planning and future policy, but also for increasing our understanding of disease risk,” said researchers.

A retrospective analysis was conducted using data from 5 epidemiological cohorts in North America in a common year, 2012: Kaiser Permanente Northern California, Honolulu–Asia Aging Study, Rochester Epidemiology Project, US Medicare program, and Ontario health administrative databases. The cohorts contained data on 6.7 million person-years of adults 45 years and older and 9.3 million person-years of adults 65 years and older.

By aggregation of the available data, age- and sex-stratified PD incidence estimates were derived. The spatial clustering of PD risk was additionally explored via Bayesian hierarchical modeling and smoothing.

Estimates of age- and sex-adjusted incidence of PD were shown to range from 108 to 212 per 100,000 among persons 65 years and older, and from 47 to 77 per 100,00 among persons 45 years and older. Prior PD incidence rates, based on smaller studies, were estimated to be in the 40,000 to 60,000 range per year. The new incidence rate was found to be 1.5 times higher at nearly 90,000 cases annually.

PD incidence estimates increased with age in the decades 65 to 74 years and 75 to 84 years in every study sample, and a higher incidence of PD was observed among males compared with females at all ages.

A clustering of counties with a higher incidence of PD was also shown in southern California, southeastern Texas, central Pennsylvania, Florida, and the “Rust Belt,” which consisted of parts of the northeastern and midwestern United States with a history of heavy industrial manufacturing. Lower incidence areas included the Mountain West region, the western Midwest, and the far Northwest.

“Unique to this study, we found that PD incidence estimates have varied for many reasons, including how cases are identified and the geographic location of the study,” said Allison Willis, MD, lead author of the study and associate professor of neurology in the Perelman School of Medicine at the University of Pennsylvania, in a press release. “The persistence of the PD belt in the United States might be due to population, health care, or environmental factors. Understanding the source of these variations will be important for health care policy, research, and care planning."

Brian Fiske, PhD, coauthor of the study and chief scientific officer at The Michael J. Fox Foundation for Parkinson’s Research, added, “The growth in those diagnosed and living with PD underscores the need to invest in more research toward better treatments, a cure, and one day, prevention. It’s also a clear call to lawmakers to implement policies that will lessen the burden of PD on American families and programs like Medicare and Social Security.”

Reference

Willis AW, Roberts E, Beck JC, et al. Incidence of Parkinson disease in North America. NPJ Parkinsons Dis. 2022;8(1):170. doi:10.1038/s41531-022-00410-y