To determine the impact of liver fibrosis on motor symptoms in Parkinson’s disease.

Parkinson’s disease motor symptoms can vary with systemic illnesses. Liver disease is associated with parkinsonism, but the impact of hepatic dysfunction on the motor manifestations of Parkinson’s disease remains unknown.

We conducted a retrospective cohort study using data from the Parkinson’s Progression Markers Initiative. Liver disease was defined using the validated Fibrosis-4 (FIB-4) score. Our primary outcome was the association of the baseline FIB-4 score with Unified Parkinson’s Disease Rating Scale (UPDRS) part 3 score. Additional outcome measures were the UPDRS part 2 and 4 scores, Hoehn and Yahr stages and levodopa equivalent daily dose. We used linear regression models to assess the relationship between liver fibrosis and motor scores at baseline and linear mixed models to evaluate the association between baseline FIB-4 score and the rate of change in motor function over five years. Models were adjusted for demographics, comorbidities, alcohol use, time since Parkinson’s disease diagnosis, and genetic predisposition.

We included 360 people with Parkinson’s disease (mean age 61.8, 41.1% women). There was a significant association between liver fibrosis and baseline UPDRS part 3 score (β=2.3, 95% CI: 0.2, 4.5). Five years later, there was no significant association between baseline FIB-4 and motor assessment scores. In the subset of patients with elevated FIB-4 scores, the rate of change in UPDRS part 3 scores was slower. There was no association between FIB-4 score and the rate of progression of other motor symptoms.

In people with Parkinson’s disease, the presence of comorbid liver fibrosis was associated with more severe motor dysfunction early, but not later, in their disease course. Further work is required to determine the underlying mechanism.