Predictors of quality of life in people with Parkinson's disease: evidence for both domain specific and general relationships.

Purpose: To assess the determinants of health-related quality of life (HrQoL) in people with Parkinson's disease (PD).

Method: Eighty-one people with a diagnosis of idiopathic PD took part in a cross-sectional questionnaire-based study. Measures were collected in a community setting and included established determinants of HrQoL (demographic, clinical and cognitive variables) but also included a wide range of mental health variables (depression, anxiety and stress) and, for the first time, positive psychological functioning (optimism and self-esteem). HrQoL was measured by the full version of the Parkinson's Disease Questionnaire (PDQ-39) which includes eight domains of functioning.

Results: Mental health measures (depression, anxiety and stress) were more influential than any other block of determinants and influenced a broader array of HrQoL domains including physical ones. There was some evidence of domain-specific relationships, e.g. between physical determinants and the more physically-oriented HrQoL domains, and between mental health determinants and emotional well-being. However, cognitive ability did not influence the HrQoL domain of cognitive impairment.

Conclusions: The contribution of a multi-disciplinary approach is crucial given the many variables which affect HrQoL; in particular, significant overall improvements on HrQoL are unlikely if only physical rehabilitation is offered. Rehabilitation is likely to be beneficial in terms of HrQoL only if it is planned and delivered holistically. Implications for Rehabilitation Interventions to improve physical function may have only limited impact on quality of life and might be limited to more physical HrQoL domains. Psychological interventions have the potential to improve quality of life over a wider range of both emotional and physical HrQoL domains. Clinician-measured level of functioning does not necessarily translate into patient-perceived levels of functional ability and relatively small objective decreases in ability can be appraised much more significantly disabling by people with PD.