OBJECTIVES : A recent report has suggested that appendectomies increase the risk of Parkinson's disease (PD); however opposite results have also been reported. Additionally, it has been suggested that PD may onset in the gastrointestinal tract and spread via the vagus nerve to the brain. Our study aims to examine the relationship between surgeries, including appendectomies, and the development of PD, by using US claims data.

METHODS : Nested case-control study was conducted using MarketScan Commercial database (2013-2017), including 78,827,151 individuals. Cases were defined as those having PD diagnosis (coded as 332/G20 by ICD-9/ICD-10 at least once) with ≥1 year of observation period before the earliest diagnosis of PD (defined as first diagnosis). Controls were non-PD individuals and matched by birth date, sex, date of start and end of observation period. Surgeries conducted before first diagnosis of PD were compared between the two groups.

RESULTS : Among a total of 43,768 PD patients in the database, 13,951 patients had ≥1 year of observation period. Matched patients analyzed in this study were 13,927 (average [standard deviation] age: 56.7 [10.6], female: 42%, observation period: 28.8 [13.2] months) in each group. The percentage of case patients who received appendectomies (0.22%) was lower than that of the control group (0.27%), but the difference was not significant (P = 0.1657). Drain/injection joint/bursa without ultrasound was the most frequently performed surgery on case patients (14.8%), followed by biopsy skin lesion (11.8%) and esophagogastroduodenoscopy biopsy single/multiple (10.6%) with significant difference. In addition, the fourth, fifth, and seventh most frequently conducted surgeries in case patients with significant difference were also interventions on digestive system.

CONCLUSIONS : No relationship, either positive or negative, was found between appendectomies and PD onset in this study. Other surgeries often conducted for PD patients, in particular those on digestive system, may be associated with development of PD.