Introduction: Health-related quality of life (HRQL) in Parkinson's disease (PD) is an area that is receiving a growing amount of interest as the new biopsychosocial model of medicine is adopted. AIM. This paper is the second part of a review of the current state of the art concerning HRQL in PD and focuses on its main determining and associated factors.
Development: A total of 56 studies are reviewed and the determining factors are grouped according to different variables, which may be disease-related (including motor and non-motor symptoms), sociodemographic (level of schooling, economic factors, gender and others), psychological and related to mental status (depression, anxiety, cognitive impairment, physician-patient relationship and others), and disability. The following characteristics of the studies were taken into account: the type of design (longitudinal or cross-sectional), the instrument used for measuring the HRQL (generic or specific), the statistical method employed (univariate or multivariate) and the sample size.
Conclusions: Most of the studies are cross-sectional and the majority use the 39-item Parkinson's Disease Questionnaire as a measure of HRQL with multivariate data analysis. The three most important factors determining HRQL in PD are depression, the stage of the disease and the time elapsed since onset of the disease. Nevertheless, the preferred methodology does not allow for causal inferences, due to the scarcity of longitudinal studies.