Parkinson’s Disease Cases Diagnosed Each Year Are 50% Higher Than Prior Estimates, With Increased Incidents in Certain Areas

A new study suggests that cases of Parkinson’s disease diagnosed each year are substantially higher than prior estimates, and the increasing numbers may be due to a variety of factors, including the widespread use of the weed killer Paraquat, which many are now indicate should be banned in the U.S.

A group of researchers known as the Parkinson’s Foundation P4 Group published findings last month in the medical journal NPJ Parkinson’s Disease, indicating new Parkinson’s disease cases are rising at a rate 50% higher than previously estimated, with about 90,000 new cases now recognized every year nationwide.

Parkinson’s disease is a neurodegenerative disorder that causes central nervous system damage, often leading to movement problems, including stiffness and tremors. The condition can be treated, but there is no cure and it is often debilitating.

Researchers with the P4 group conducted a study to investigate the incidents of Parkinson’s disease cases in the U.S., investigating the prevalence across various epidemiological cohorts and regions. Researchers looked at data on 6.7 million person-years of adults 45 years old and older, and 9.3 million person years of adults ages 65 and older.

“Our estimates of age-sex-adjusted incidence of PD ranged from 108 to 212 per 100,000 among persons ages 65 and older, and from 47 to 77 per 100,00 among persons ages 45 and older. PD incidence increased with age and was higher among males,” the researchers reported. “We also found persistent spatial clustering of incident PD diagnoses in the U.S. PD incidence estimates varied across our data sources, in part due to case ascertainment and diagnosis methods, but also possibly due to the influence of population factors (prevalence of genetic risk factors or protective markers) and geographic location (exposure to environmental toxins). Understanding the source of these variations will be important for health care policy, research, and care planning.”

The researchers found that the incidence of Parkinson’s disease cases increased with age, and was substantially higher in certain areas of the U.S., including counties in the Midwestern and Southern regions country, as well as parts of southern California, southeastern Texas, central Pennsylvania and Florida. The researchers found lower incidence rates in the Mountain West, western Midwest and far Northwest regions of the country.

Beyond age, researchers did not have an explanation for the high Parkinson’s disease rates, which were about 50% higher than previously anticipated. There could be a variety of factors, including the aging population of the U.S., an increased awareness of the disease, genetic factors or environmental risks.

Paraquat Parkinson’s Disease Risks

In recent years, studies have linked exposure to the herbicide Paraquat to an increased risk of Parkinson’s disease. The widely used herbicide has been blamed for causing higher rates of Parkinson’s disease cases among farmers and workers in the agricultural community, who were exposed to the chemical while mixing, spraying and handling Paraquat, or being in the area where it was applied to fields.

Although Paraquat is already heavily restricted in the United States due to the risk of life-threatening toxicity if even a small amount of the weed killer is ingested, there are now a growing number of Paraquat lawsuits being pursued by former users diagnosed with Parkinson’s disease, indicating that studies have found exposure may be linked to a two- to five-fold increased risk among individuals regularly handling, mixing and spraying Paraquat, compared to populations that do not have such occupational exposure.

There are currently more than 2,000 product liability cases filed against Syngenta and Chevron in the federal courts, each raising similar allegations that the companies failed to warn farmers and agricultural users about the link between Paraquat and Parkinson’s disease, which research has found may develop years after regularly spraying, mixing, transporting or handling the weed killer.

Given common questions of fact and law raised in the litigation, the federal cases have been centralized as part of a Paraquat MDL (multi-district litigation), which is consolidated before U.S. District Judge Nancy J. Rosenstengel in the Southern District of Illinois, for coordinated discovery and pretrial proceedings.