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

BackgroundPain 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.ObjectivesTo assess the relationship between pain, fatigue, and mediating variables in PD.MethodsFifty-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.ResultsFatigue 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.ConclusionA 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.