Nonmotor versus motor symptoms: how much do they matter to health status in Parkinson's disease?

Evidence suggests that both motor and nonmotor symptoms contribute to health status in Parkinson's disease. Less clear is how much change in health status can be expected if these clinical variables change. In addition, anxiety, separate from depression, has rarely been examined as a predictor of health status. We used hierarchical multiple regression analysis and standardized beta coefficients in a prevalent cohort of 462 patients with Parkinson's disease to explore the relative impact on health status (measured using the Parkinson's Disease Questionnaire) of 5 well-recognized symptom domains in Parkinson's disease: motor signs, depression, anxiety, cognition, and other nonmotor symptoms. In the health status scores, 19.6% of variance was explained by age, number of comorbidities, disease duration, and levodopa equivalent dose. Younger age predicted worse health status. A full regression model containing baseline variables and all 5 symptom domains explained 56% of the variance in health status. The standardized beta coefficient for depression was 2.1, 1.6, and 1.3 times that of motor signs, anxiety, and other nonmotor symptoms, respectively. Our findings provide a ranking order of clinical variables for their relative impact on health status in Parkinson's disease and show that depression has more than twice the impact of motor signs on health status. Anxiety and other nonmotor symptoms are also important separate determinants of poor health status in Parkinson's disease. Our results will help to guide the development of individual care and service planning for patients with Parkinson's disease.