Quantitative Evaluation of Respiratory Dysfunction and Its Relationships With Parkinson's Disease Symptoms

Respiratory disorders significantly impair functional baseline and quality of life (QoL) in Parkinson's disease (PD). This cross-sectional study aimed to evaluate spirographic lung function parameters in PD and determine their relationships with motor and nonmotor symptoms, QoL, and dopaminergic therapy. Spirometric parameters were recorded in 57 outpatients with PD and 10 healthy controls. PD patients underwent clinical assessments using UPDRS Parts II and III, Schwab and England scale, PDQ-39, and PFS-16. Spirometric analysis revealed significant decreases in VC %pred in PD patients versus controls, and in FVC %pred in PD Stage III versus PD Stage II. Decreased lung function correlated with H&Y stage (VC, FVC, FEV1) and showed inverse correlations with UPDRS Parts II and III scores, most pronounced for axial-locomotor impairments (posturing, gait, stability, arising from chair) and bradykinesia. PFS-16 fatigue index inversely correlated with FEV1 and PEF. Worse QoL (PDQ-39 summary index, emotional well-being, and cognition domains) was primarily coupled with decreased expiratory flow rates (FEV1, PEF). Untreated PD patients exhibited significantly lower FVC%pred, FEV1%pred, FEF75%pred, and Tiffeneau index than those on dopaminergic therapy. This study demonstrates the presence of respiratory dysfunction in PD Stages II and III and its negative association with QoL. The results highlight the relationship between lung function decline and overall PD progression, with the strongest associations revealing the most significant contribution of postural abnormalities, bradykinesia, and pathological fatigue. Furthermore, the obtained data suggest a potential compensating role of dopaminergic therapy.