Quality of life in Parkinson's disease patients: progression markers of mild to moderate stages.

Objective: To investigate which factors are associated with the quality of life decline in Parkinson's disease patients from mild to moderate stages.

Methods: The Unified Parkinson's Disease Rating Scale and Parkinson's Disease Questionnaire-39 were used to evaluate clinical/functional data and the quality of life.

Results: The markers of clinical/functional worsening were drooling (p < 0.