Parkinson’s disease (PD) is a chronic condition that imposes a substantial burden on patients and their caregivers. The disease has a profound and progressive impact on various neurological functions, but its aetiology is not fully understood. There are an estimated seven to 10 million people with PD worldwide (including 1.2 million in Europe); it is the second most common neurodegenerative disease after Alzheimer’s disease.1-4 In PD, advancing age is a strong risk factor and its prevalence is likely to increase with demographic changes leading to increasingly elderly populations. 5 In Europe, the disease costs an estimated €13.9 billion per year (in 2012) 6,7 compared with an estimated €126 billion/year for cancer (in 2009)8 and an estimated €196 billion/year for cardiovascular disease (in 2012). 9 An increasingly recognised and important factor in PD is its impact on quality of life (QoL) and its assessment is becoming more important in clinical trials and routine practice. 10 Perspectives of QoL in PD as seen by patients, in clinical practice and in research can be quite different. For example, PD involves prominent motor symptoms such as slowness (bradykinesia) and stiffness (rigidity) that are a primary concern for patients, 11 but also causes a variety of non-motor symptoms that are frequently overlooked and/or unreported. 12,13 It is important that these perspectives are aligned to fully assess the differing impact of the disease on each patient and better monitor the effects of treatment. This article considers QoL in PD from different perspectives and a companion article in this issue continues this theme with the effect of therapeutic measures and QoL outcomes in PD in clinical trials. 14 Both articles are based on the discussions of an expert panel on QoL in PD that was convened at the 20th World Congress on Parkinson’s Disease and Related Disorders, Geneva, December 2013.
What is Quality of Life and What Scales are used in Parkinson’s Disease?
QoL is a general term relating to an individual’s overall well-being and satisfaction. This is a holistic approach encompassing various aspects of a patient’s condition and is gaining recognition as an important measure of disease impact and status. QoL is also a criterion that can be improved with treatment rather than simply concentrating on specific disease symptoms. 15 Health-related QoL (HRQoL) is a component of QoL and is a patient-reported outcome, with physical, mental and social domains that can be measured at single points and over time periods.
HRQoL scales may be generic and applicable to multiple different diseases, such as multiple sclerosis, Alzheimer’s disease, stroke and depression and include, for example, the EuroQoL-5D (EQ-5D) or Short Form-36 (SF-36). Some scales, however, are PD-specific, such as the 8- and 39-item Parkinson’s Disease Questionnaires (PDQ-8/PDQ-39), Parkinson’s Impact Scale (PIMS), Scales for Outcomes in Parkinson’s Disease – Psychosocial questionnaire (SCOPA-PS) or the Parkinson’s Disease Quality of Life scale (PDQUALIF) (see Table 1).16
The most commonly used HRQoL instruments characterise patients in multiple dimensions, e.g., disease symptoms, physical functioning, emotional well-being and social activity. 17 In PD, these measures of HRQoL provide important global information for assessing the efficacy of medical interventions. 10 The SF-36 questionnaire is the most widely used generic measure and gathers information of the patient’s physical and mental status, which are presented as two different sub-scores. The physical component summary encompasses physical functioning, physical role, bodily pain and general health; the mental health component encompasses vitality, social functioning, emotional role and mental health. This measure has been successfully used to assess the status of various diseases in clinical practice including PD. This scale, however, has limitations in assessing change in physical health but is useful in predicting the course of disease. 10,18,19
The EQ-5D is another generic measure of HRQoL that is frequently used in PD and is a five-dimension questionnaire dealing with aspects related to mobility, self-care, usual activities, pain/discomfort and anxiety/depression. 20 Other prominent generic HRQoL scales in PD include: the Quality of Life Questionnaire 15D, 21 the Schedule for the Evaluation of Individual Quality of Life-Direct Weighting22 and the World Health Organization Quality of Life Assessment Short Version. 16