Impact of non-motor symptoms on health-related and perceived quality of life in Parkinson's disease.

OBJECTIVE: To investigate the impact of non-motor symptoms on health-related and perceived quality of life in Parkinson's disease (PD).
METHODS: One hundred and fifty PD patients (57.3% males; 70.9±8.6years old) were included in this cross-sectional, monocenter, evaluation study. Multiple linear regression methods were used to evaluate the direct impact of non-motor symptoms (as assessed by the Non-Motor Symptoms Scale [NMSS]) on 1) the 39-item PD Quality of Life Questionnaire Summary Index score (PDQ-39SI), and 2) a subjective assessment of perceived quality of life (PQ-10), after adjusting for age, sex, mood (Beck Depression Inventory), disability (Schwab&England Activities of Daily Living Scale), and PD-specific motor dysfunction (ON-state Hoehn&Yahr/Unified Parkinson's Disease Rating Scale [UPDRS] part III, and motor complications [UPDRS part IV]).
RESULTS: Higher NMSS total scores were systematically associated with worse quality of life (for PDQ-39SI, p=0.013; for PQ-10, p=0.017). PD-specific motor dysfunction had a larger negative impact on health-related quality of life (PDQ-39SI) than non-motor symptoms (2.8% vs 0.7%). In contrast, the negative impact of non-motor symptoms on perceived quality of life (PQ-10) was larger than that found for PD-specific motor dysfunction (2.8% vs 0.9%). While the model for PDQ-39SI provided an adequate fit (adjusted R-squared, 0.83), a substantial proportion of the PQ-10 variance remained unexplained (adjusted R-squared, 0.48).
CONCLUSIONS: Non-motor symptoms have a direct negative impact on health-related and perceived quality of life in PD. Perceived quality of life is not adequately explained by motor and non-motor manifestations of the disease.