Cosmos Study

Parkinson’s Diagnoses Highest in Nebraska and Kansas

October 21, 2025

Team A:Kersten Bartelt, RNEmily Higgs

Team B:Blaine Franklin, PT, DPTGrant Keane

Key Findings

Nebraska and Kansas have the highest rates of Parkinson’s disease among U.S. states studied, with 620 and 596 people diagnosed per 100,000 patients, respectively. Even after adjusting for other factors like age, sex, and comorbidities, Nebraska and Kansas continue to have the highest rates among U.S. states, suggesting the elevation is not solely due to demographics.

Parkinson’s disease, a progressive neurodegenerative disorder, is considered a multi-factorial disease influenced by genetic factors, comorbidities, and environmental exposures such as air pollution and chemicals used in manufacturing and agriculture.¹ Understanding geographic patterns of Parkinson’s diagnoses can offer important clues about potential environmental contributions and regional differences.

We studied more than 46 million adult patients across 49 U.S. states who had at least three outpatient visits between 2020 and 2025 to better understand patterns of Parkinson’s diagnoses. Data for Alaska were too sparse to conduct a meaningful analysis. We first examined the unadjusted incidence rates for each state and then calculated an adjusted rate that accounted for age, sex, and comorbidities.

When looking at unadjusted incidence rates, we found that Nebraska (620 per 100,000 patients) and Kansas (596 per 100,000 patients) had the highest rates of newly diagnosed Parkinson’s disease during the study period. States with the lowest observed rates were Montana (264 per 100,000 patients) and Nevada (275 per 100,000 patients).

After adjusting for patient age, time in the study, sex, race, ethnicity, and comorbidities, a relative rate was established for each state compared to Minnesota, the median for overall rates. Nebraska and Kansas remained the highest with 561 diagnoses per 100,000 patients and 517 diagnoses per 100,000 patients, respectively. Utah had the third highest rate at 493 diagnosed per 100,000 patients. States with the lowest relative rates were Montana (308 per 100,000 patients), Wisconsin (329 per 100,000 patients), and Washington (339 per 100,000 patients).

Figure 1

Parkinson’s Diagnosis Rate by State

Figure 1. The rate of Parkinson’s diagnoses per 100,000 adult patients per state. The adjusted rates account for patient age, sex, race, ethnicity, and comorbidities.

These data come from Cosmos, a dataset created in collaboration with a community of Epic health systems representing more than 300 million patient records from 1,800 hospitals and more than 41,000 clinics from all 50 U.S. states, Canada, Lebanon, and Saudi Arabia. This study was completed by two teams that worked independently, each composed of a clinician and research scientists. The two teams came to similar conclusions. Graphics by Brian Olson.

References

Tanner CM, Ostrem JL. Parkinson’s disease. N Engl J Med. 2024;391(5):442-452. doi:10.1056/NEJMra2401857

Data Definitions

Study period: 1/1/2022 to 6/1/2025

Study population: inclusion

Patients with:

An outpatient face-to-face visit within 2020 to 2021, 2022 to 2023, and 2024 to 2025
An age of 20 or greater as of 1/1/2022

Study population: exclusion: Any diagnoses of Parkinson’s prior to 1/1/2022
Patients whose residence is outside of the United States

Outpatient face-to-fact visit: An encounter of type Emergency, Office Visit, Well Child, Follow-Up, Telemedicine, Urgent Care, Walk-In, Routine Prenatal, Postpartum Visit, Fetal Care Consult, or Hospital Outpatient Visit

Exposures: Patient’s state of residence as of their most recent healthcare encounter

Parkinson’s: A diagnosis with ICD-10-CM code G20* or SNOMED code 49049000

Confounders

Reliable sex
Age

<=34
35-49
50-64
65-74
75-84
85+

History of TBI
History of type 2 diabetes
History of CVD
Race and ethnicity

TBI (traumatic brain injury): A diagnosis with ICD-10-CM code S06* or SNOMED code 127295002

Type 2 diabetes: A diagnosis with ICD-10-CM code E11*

CVD (cardiovascular disease): A diagnosis with ICD-10-CM code I20*-I26*, I30*-I39*, I40*-I49*, I51*, or I70*-I79*

Race and ethnicity: Patients were classified by self-reported race and ethnicity as Hispanic (any race), multiracial, non-Hispanic Black only (Black), non-Hispanic White only (White), non-Hispanic Asian only (Asian), other, or unknown

Model specifications

Rates per state
Adjusted model:

Incidence density sampling matching patients 1:4 on age bucket and time in the study
Survival analysis adjusting for confounders to get a hazard ratio per state
Formula: MN unadjusted rate * the state of interest’s hazard ratio