Frequency of Parkinson disease following COVID-19 infection: A two-year retrospective cohort study

Introduction: COVID-19 infection is known to cause various neurological symptoms, and potentially increases the risk of developing subsequent neurodegenerative conditions including parkinsonism. To our knowledge, no study to date has used a large data set in the United States to ascertain the risk of developing incident Parkinson disease in patients with history of COVID-19 infection compared to the risk amongst those without prior COVID-19 infection. Methods: We utilized data from TriNetX electronic health records network which includes 73 healthcare organizations and over 107 million patients. We compared adult patients with and without COVID-19 infection, with health records from January 1, 2020 through July 26, 2022, to determine the relative risk of developing Parkinson disease stratified by 3-month intervals. We used propensity score matching to control for patients' age, sex, and smoking history. Results: We collected data on 27,614,510 patients meeting our study criteria: 2,036,930 patients with a positive COVID-19 infection (COVID-19) and 25,577,580 without a positive COVID-19 infection (non-COVID-19). After propensity score matching, age, sex, and smoking history differences became non-significant, with 2,036,930 patients in each cohort. After propensity score matching, we found significantly increased odds of new onset Parkinson disease in the COVID-19 cohort at three, six, nine, and twelve months from the index event, with peak odds ratio at six months. After twelve months there is no significant difference between the COVID-19 group and non-COVID-19 group. Conclusions: There may be a transiently increased risk of developing Parkinson disease in the first year following COVID-19 infection.