Association between respiratory function and motor function in different stages of Parkinson's disease

Introduction: Respiratory dysfunction in patients with Parkinson's disease (PD) could present in the early stage and worsen in the late stages. These changes could be a factor affecting the ability of daily living and quality of life of patients with PD. The primary objective of this study was to assess the respiratory function and its association with motor function in patients with different stages of PD. Methods: This was a cross-sectional study conducted at the Huashan Hospital of Fudan University in Shanghai, China. The study included 65 patients diagnosed with PD (the Hoehn & Yahr scale between 1 and 4) and 20 healthy individuals of similar age, gender, weight and height. The ventilatory function was assessed using the spirometry. Motor function was evaluated using subscale III of the United Parkinson's disease rating scale (UPDRS-III). After confirming the normality of data distribution, we performed one-way ANOVA with a Tukey's post-hoc test. Results: Compared with the healthy individuals, there was no statistical significance in forced vital capacity (FVC), forced expiratory volume in 1s (FEV1) and forced expiratory volume in 1s/forced vital capacity (FEV1/FVC) in the H & Y 1 group and H & Y 2 group (P>0.05); but reduced peak expiratory flow (PEF) in the H & Y 2 group (P=0.002). Reduced FVC?FEV1 and PEF was seen in the H & Y3 group (P=0.002, P=0.001 and P=0.0001, respectively). Reduced FVC?FEV1?PEF and FEF25-75% was seen in the H & Y4 group (P=0.001, P=0.0001, P=0.0001 and P=0.025, respectively). The correlation analysis revealed that there was a significant negative correlation between FVC and UPDRS-III scores (r=-0.248, P=0.046), disease duration (r=-0.276, P=0.026), H & Y scale (r=-0.415, P=0.001). FEV1 was negatively correlated with UPDRS-III scores (r=-0.277, P=0.025), disease duration (r=-0.291, P=0.019), H & Y scale (r=-0.434, P=0.0001). FEF25%-75% was negatively correlated with disease duration (r=-0.247, P=0.047), H & Y scale (r=-0.278, P=0.025). Conclusion: Our findings revealed that respiratory impairment is present in moderate and advanced PD patients, and directly related to the severity of the disease. It is important to conduct respiratory function test in the clinical practice.