Relationships between disability, quality of life and prevalence of nonmotor symptoms in Parkinson's disease

Patients with Parkinson's disease suffer from a variety of motor and nonmotor symptoms (NMS), report reduced quality of life and increased disability. Aims of this study are to assess the impact of Parkinson's disease on disability and quality of life, to evaluate the relationships between them and NMS prevalence. In this cross-sectional study, adult patients were consecutively enrolled and administered the World Health Organization Disability Assessment Schedule (WHO-DAS II), the 36-Item Short-Form Health Survey (SF-36) and the Non Motor Symptoms Questionnaire (NMSQuest). One-sample t-test was used to compare WHO-DAS II and SF-36 scores with normative value. Pearson's correlation was performed between NMSQuest, WHO-DAS II and SF-36 summary scales. Independent-sample t-test was used to compare NMSQuest, WHO-DAS II and SF-36 scores in patients with Hoehn & Yahr stage <3 and ≥ 3. In total, 96 patients were enrolled. SF-36 and WHO-DAS II scores were significantly worse than the normative values. Correlation coefficients between NMSQuest, WHO-DAS II and SF-36's mental score were moderate, and were high between WHO-DAS II and and SF-36's physical score. Patients with Hoehn & Yahr stage ≥ 3 reported reduced quality of life, higher disability and more NMS. Parkinson's disease severity is strongly associated with reduced quality of life, increased disability and NMS prevalence. Disability and quality of life assessment tools measure psychosocial facets that are similar specifically with regard to physical health component of health-related quality of life, are sensitive enough to capture differences related to disease's progression and increased prevalence of NMS.