Determinants of disability and quality of life in mild to moderate Parkinson disease

Objective: To identify factors that independently contribute to disability and quality of life (QoL) in patients with mild to moderate Parkinson disease (PD). Methods: A group of 190 patients with PD recruited from outpatient clinics and the Dutch Parkinson's Disease Association participated in this cross-sectional study. Data on demographic and clinical factors, motor symptoms, cognitive functions, affective symptoms, comorbidity, and social support were collected during neurologic and neuropsychological examinations. Disability was rated using the Schwab and England Activities of Daily Living Scale (SE-ADL), the AMC Linear Disability Score (ALDS), and the Functional Independence Measure (FIM). QoL was assessed with the Parkinson's Disease Quality of Life questionnaire (PDQL) and the Medical Outcome Study Short Form (SF-36). Multiple linear regression analyses were conducted to identify determinants of disability and poor QoL. Results: Axial impairment (postural instability and gait difficulty) explained the largest proportion of variance in disability. Bradykinesia and comorbidity contributed to disability, but to a lesser extent. Self-reported mood symptoms and axial impairment were the two factors most closely associated with poorer QoL, but comorbidity and bradykinesia additionally contributed to the explanatory power. Semantic fluency and psychomotor skills were the only cognitive variables related to some aspects of functional outcome. Conclusion: Axial impairment is strongly associated with disability in patients with mild to moderate Parkinson disease (PD). Self-report indices of mood status and axial impairment are identified as the main determinants of poor quality of life (QoL). The results of this study may help to identify patients with PD at risk for functional dependence and reduced QoL.