The Cognition and Emotional Well-being indices of the Parkinson's disease questionnaire-39: What do they really measure?☆
Introduction
Health related quality of life (HRQoL) refers to the broad physical, emotional and social wellness of individuals and is influenced by various health conditions including Parkinson's disease (PD) [1]. Parkinson's disease is a neurodegenerative disorder classically identified by motor symptoms (resting tremor, rigidity, bradykinesia) but also consisting of non-motor symptoms, including cognitive and mood changes. The influence of non-motor symptoms on HRQoL may be particularly important in PD as previous findings have suggested that non-motor symptoms are stronger determinants of HRQoL than motor symptoms [2], [3].
The Parkinson's disease questionnaire-39 (PDQ-39) is one of the most widely used measures of HRQoL in individuals with PD [4]. The PDQ-39 assesses HRQoL across eight domains: mobility, activities of daily living (ADL), emotional well-being, stigma, social support, cognitions, communication and bodily discomfort. However, limited research has examined the validity of these separate domains. This is important for at least two reasons: 1) the atheoretical development of the eight indices, and 2) questionable evidence regarding the psychometric properties of some of the PDQ-39 domains.
First, the identification of the eight domains of the PDQ-39 relied on the atheoretical fit of items based on factor analysis [5]. Briefly, the development of the PDQ-39 included interviews with 20 patients in order to identify areas of life that have been negatively influenced by PD. This resulted in a 65-item questionnaire, which was mailed to a large group (N = 359) of PD patients. From this sample, a factor analysis was conducted, which found 10 factors. Two factors were deemed inconsistent/repetitive and were removed by the authors in order to reduce the number of items. Overall, this process resulted in a final set of 39 items representing eight factors or “domains” of the PDQ-39. Secondly, research has shown that some items have only moderate correlations with their respective domains [6], [7]. Misfit of items may be particularly questionable for the Cognitions index, as items frequently correlate stronger with other domains [7].
To date, validation of the PDQ-39 has focused on the external/convergent validity of the overall PDQ-39 Summary Index against other HRQoL and clinical measures, including the SF-36 Health Survey Questionnaire, the Hoehn Yahr Scale and the Columbia University Rating Scale [4], [5], [8]. To our knowledge the Cognitions and Emotional Well-being indices have not been examined for external/convergent validity. This is particularly relevant for the Cognitions index since two of the four items comprising the subscale do not directly refer to cognition; one item refers to unexpectedly falling asleep during the day and another item refers to the presence of distressing dreams or hallucinations.
The current study had two goals. The first goal was to examine the convergent validity of the PDQ-39 Cognitions index against standardized measures of neuropsychological performance. It was predicted that if the Cognitions index is sensitive to domains of HRQoL negatively affected by cognitive impairment then there should be a strong link between the Cognitions index and neuropsychological measures. This would be especially robust for measures of memory, executive function, and processing speed; all areas affected by PD. Thus, worse performance on memory, executive, and/or processing speed measures would be associated with higher scores on the Cognition Index (meaning worse endorsement). The second goal was to examine the convergent validity between the Emotional Well-being scale and standard measures of psychological distress, including apathy, depression and anxiety. It was predicted that if the Emotional Well-being scale is a measure of HRQoL affected by mood disturbances common in PD then there would be a strong relationship between the Emotional Well-being index and measures of apathy, depression and anxiety.
Section snippets
Design & participants
A cross-sectional design included a convenience sample of 303 patients with idiopathic Parkinson's disease according to UK Brain Bank criteria [9]. The study received approval from the University of Florida Institutional Review Board. Consent was attained prior to patient participation. All patients underwent a comprehensive neuropsychological assessment, including completion of mood and HRQoL questionnaires, between January 2006 and September 2010 as part of their routine clinical care through
Sample characteristics
Table 1 shows the sample characteristics of the 303 Parkinson patients. Overall, the sample was 69% male and 88% Caucasian; with a mean age of 64.7 and 15 years of education. Average duration of motor symptoms was 9.7 years and a mean UPDRS motor (on medication) score of 26.3. The average Dementia Rating Scale-II score and PDQ-39 Summary Index were 137.2 and 29.5, respectively.
PDQ-39 cognitions and neuropsychological domains
Pearson's correlations revealed a significant, although small correlation between the PDQ-39 Cognitions score and the
Discussion
There are two main findings resulting from this study. First, this study found that the PDQ-39 Cognitions index was not broadly related to performance across multiple neuropsychological domains, and only minimally correlated with tests of delayed verbal memory and processing speed. Instead, mood, especially depression, showed a stronger relationship to the PDQ-39 Cognitions index score than did the neurocognitive measures. Secondly, the PDQ-39 Emotional Well-being domain was significantly
Conclusion
While the Emotional Well-being index of the PDQ-39 showed a moderate relationship to measures of depression and anxiety, the Cognitions index was unrelated to cognitive functioning. Rather than measuring HRQoL specific to cognitive functioning, the Cognitions index may be measuring a separate construct (possibly depression or arousal/sleep efficiency). An important take home message is that the Cognitions index is not a “proxy” for cognitive functioning, and future studies are needed to better
Author roles
Jacob Jones: Study concept, data analysis, interpretation, initial paper draft.
Chris Hass: Study concept, revision of draft.
Paul Mangal: Study concept, organization, revision of draft.
Jacob Lafo: Study concept, organization, revision of draft.
Michael Okun: Study concept, revision of draft.
Dawn Bowers: Study concept, study supervision and coordination, interpretation, review of all written drafts.
Financial disclosure/conflict of interest
Mr. Jones, Mangal, Lafo & Dr. Hass do not have any financial disclosures to report.
Dr. Okun serves as a consultant for the National Parkinson Foundation, and has received research grants from NIH, NPF, the Michael J. Fox Foundation, the Parkinson Alliance, Smallwood Foundation, the Bachmann-Strauss Foundation, the Tourette Syndrome Association, and the UF Foundation. Dr. Okun has previously received honoraria, but in the past >60 months has received no support from industry. Dr. Okun has
Acknowledgment
This study was supported by the infrastructure from the National Parkinson Foundation Center of Excellence, the UF INFORM database, and the UF Foundation.
References (26)
Quality of life and depression in Parkinson's disease
J Neurol Sci
(2006)- et al.
Factors affecting the quality of life of patients with idiopathic Parkinson's disease-a cross-sectional study in an outpatient clinic attendees
Park Relat Disord
(2005) - et al.
Validity and reliability of the PDQ-39 and the PDQ-8 in English-speaking Parkinson's disease patients in Singapore
Park Relat Disord
(2004) - et al.
Quantification of five neuropsychological approaches to defining mild cognitive impairment
Am J Geriatr Psychiatry
(2009) - et al.
Subjective perception of cognition is related to mood and not performance
Epilepsy & Behav
(2009) - et al.
Quality of life and related concepts in Parkinson's disease: a systematic review
Mov Disord
(2007) - et al.
The Parkinson's disease questionnaire (PDQ-39): development and validation of a Parkinson's disease summary index score
Age Ageing
(1997) - et al.
The development and validation of a short measure of functioning and well being for individuals with Parkinson's disease
Qual Life Res
(1995) - et al.
The 39 item Parkinson's disease questionnaire (PDQ-39) revisited: implications for evidence based medicine
J Neurol Neurosurg Psychiatry
(2007) - et al.
Self-reported functioning and well-being in patients with Parkinson's disease: comparison of the short-form health survey (SF-36) and the Parkinson's disease questionnaire (PDQ-39)
Age Ageing
(1995)
Accuracy of clinical diagnosis of idiopathic Parkinson's disease: a clinico-pathological study of 100 cases
J Neurol Neurosurg Psychiatry
Comparison of beck depression Inventories-IA and-II in psychiatric outpatients
J Pers Assess
The validity of the Beck depression inventory as a screening and diagnostic instrument for depression in patients with Parkinson's disease
Mov Disord
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