The Relationship between PDQ-8 and Costs in Parkinson's Disease-A Swedish Register-Based Study

Parkinson's disease (PD) is a progressive neurodegenerative disorder associated with substantial costs which increase with progression state. However, few studies have investigated the association between costs and health related quality of life.

To estimate the relationship between costs and health related quality of life, measured by the Parkinson's disease Quality of Life Questionnaire (PDQ)-8 from a societal perspective, partial societal perspective (excluding productivity loss), and a health care perspective.

The Swedish Parkinson's Disease registry was linked to health care data registries to estimate annual costs. A generalized linear model was used to assess the relationship between instrument items and costs.

The results suggest that PDQ-8 captures the increase of costs by PD severity, particularly for costs within the broader societal perspective. From the best to worst PDQ-8 quartile, we observed approximately 7-fold increases within the societal perspective (39,400 to 274,300 SEK) and the partial societal perspective (31,800 to 219,400 SEK), and the increase within the health care perspective more than doubled (21,900 to 49,700 SEK). The PDQ-8 dimensions "mobility," "activities of daily living" and "social support" were associated with high costs in all perspectives.

Using a disease-specific measure reflecting the patient's perspective, we found an increase of costs with worsening severity of PD, particularly for costs within the broader societal perspective. High costs were associated with not only motor symptoms, but also the dimension "Social support."