Pain and Fatigue in Parkinson’s Disease: Exploring Their Interrelation and Mediating Variables

Background Pain is a non-motor symptom (NMS) of Parkinson's disease (PD) present in up to 85% of patients. Fatigue is another highly prevalent NMS. Presence of both is detrimental for the individual's well-being, but their association remains largely unexplored. Objectives To assess the relationship between pain, fatigue, and mediating variables in PD. Methods Fifty-three PD patients with pain participated in a cross-sectional study. Correlation analyses were performed between clinical, self-reported measures of pain (Spanish-King's-Parkinson-Pain-Scale (S-KPPS) and Brief-Pain-Inventory (BPI) and fatigue (Fatigue-Severity-Scale (FSS), Daily-Fatigue-Impact-Scale (DFIS)). Partial correlations were performed considering these confounders: Levodopa-equivalent daily dose (LEDD), years from PD diagnosis, UPDRS-III score, anxiety, depression and kinesiophobia. Results Fatigue severity (FSS) was positively and moderately correlated with pain interference (BPI; ρ = 0.351, p = 0.045) and symptomatic burden (S-KPPS; ρ = 0.367, p = 0.042), but not intensity (BPI; ρ = 0.122, p = 0.446). DFIS did not correlate with any dimension of pain (p > 0.05). Motor symptoms, anxiety, depression and kinesiophobia changed correlation significance, but LEDD and disease duration didn’t. Conclusion A moderate correlation was found between fatigue severity and both pain interference and symptomatic burden, influenced by other non-motor symptoms (NMS) like anxiety and depression. Although anxiety and depression have previously been associated with fatigue, this study adds pain to a tetrad of interrelated NMS prevalent in PD