The burden of Parkinson disease (PD) and concomitant comorbidities
Introduction
PD is a leading cause of neurological disability in the adult population (Damiano et al., 1999). The burden of disease associated with PD includes physical, mental and psychological impairments, which are particularly problematic with the advanced stages of the disease. Health-related quality of life (HRQL) in PD is, more often than not, measured in clinical samples using disease-specific measures (Hobson et al., 1999, Jenkinson et al., 1999, Schrag et al., 2000b), which preclude comparisons to the population without PD and limit external validity. Although HRQL has been examined in clinical patient samples, relatively few studies have used representative samples of the population to evaluate the impact of PD on HRQL (Rubenstein et al., 1997, Karlsen et al., 1999, Schrag et al., 2000a). Population-based reference data provide a comparison and further detail about the HRQL of persons with PD. Additionally, the estimates can be used for quality adjusted life years (QALYs) when evaluating the efficiency of interventions.
There are a few population-based studies of the burden of PD that have adjusted for sociodemographic characteristics beyond controlling for age and sex (Rubenstein et al., 1997, Riazi et al., 2003). Patients with PD are 2–10-times more likely to have difficulties with self-care, social functioning, mobility, anxiety and depression and also have significantly lower overall HRQL scores (Schrag et al., 2000a). These findings, however, were compared to published UK population norms, rather than measuring HRQL in both the PD and general population without the disease at a single point in time. Similarly, a population-based survey of the US general population reported significant burdens of health in persons with PD as compared to controls (Rubenstein et al., 1997). The burden of PD has also been captured, in part, by exploring the economic consequences of the disease in terms of healthcare utilization, lost productivity and caregiver costs (Rubenstein et al., 1997, Chrischilles et al., 1998, Dodel et al., 2001). The direct and indirect costs of the disease represent significant burden which have been substantiated in a number of countries (Rubenstein et al., 1997, Dodel et al., 2001, Cordato et al., 2006, Noyes et al., 2006).
Because of the substantial impact of PD on health status, the literature has called for further investigation of the disease burden (GPDSSC, 2002, Dowding et al., 2006). Comparison of HRQL to the general population is a useful means of capturing disease burden from both patient and societal perspectives. The purpose of this study was to compare the health status of community-dwelling persons who have PD to those persons without PD, using a nationally representative sample of the Canadian general population. We also examined specific chronic medical conditions to evaluate their impact on the burden of PD. This comparison to the general population will provide quantitative estimates of the impact of PD on health status and HRQL.
Section snippets
Survey design
Data from the Canadian Community Health Survey (CCHS) Cycle 1.1 were used in this analysis. Ethical approval was obtained through the University of Alberta Health Research Ethics Board. Approval to access the survey data was obtained from Statistics Canada (2004).
The CCHS 1.1 is a cross-sectional survey of the Canadian population over the age of 12 years. Data pertaining to health status, determinants of health and utilization of health services were collected between September 2000 and
Results
The average age of respondents with PD was 68.9 years (CI = 66.6–71.2) compared to 44.8 years (CI = 44.8–44.9) in the general population (Table 1). The mean duration of disease for PD was 7.3 (CI 5.6–8.9) years. More than one-half of the respondents with PD were male (56%) and a substantial proportion had not completed high school (43%). The PD and general populations did not differ significantly with respect to marital status, social assistance and sex, but some differences were noted according to
Discussion
Within a representative sample of community-dwelling persons, substantially lower health status was reported in persons with PD than the general population. In particular, health status of persons with PD was seven times lower for what is considered the clinically meaningful difference than the general population. We found that the disease affected both physical and mental dimensions of HRQL (ambulation, dexterity, emotion, cognition and pain) relative to the general population. Other
Conclusions
In summary, PD has detrimental effects on both physical and mental attributes of HRQL, resulting in a substantial HRQL burden for persons with this neuro-degenerative disease. The progressive nature of the disease with its complex treatment underscores the diverse impact of burden and the need to manage all aspects of the disease. The findings presented provide baseline population estimates of disease burden for PD with which the efficacy, effectiveness and efficiency of therapeutic
Conflict of interest
None declared.
Acknowledgements
We would like to thank the Statistics Canada for providing access to the data through the Research Data Centre at the University of Alberta and the University of Alberta for providing facilities to access the data. The research and analysis are based on data from Statistics Canada (2004). The opinions expressed do not represent the views of Statistics Canada. We also express our gratitude to Dr. David Feeny, Dr. W. Martin and Ms. Marguerite Wieler for their constructive comments. This study was
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