Influencing effect of non-motor symptom clusters on quality of life in Parkinson's disease

https://doi.org/10.1016/j.jns.2014.10.032Get rights and content

Highlights

  • PD patients with NMS may have a specific cluster pattern.

  • NMSC emerged differently depending on sex and the severity of PD.

  • Some NMSCs may have a negative effect on quality of life in PD.

  • Understanding of NMSC in PD patients may provide better therapeutic interventions.

Abstract

The heterogeneity of non-motor symptoms (NMSs) in patients with Parkinson's disease (PD) has been well established. We investigated the effects of NMS as a cluster on the quality of life (QoL) of patients with PD. We recruited 180 patients with PD and used a descriptive cross-sectional study design. To determine interrelationships between non-motor symptoms, a principal component analysis with varimax rotation was performed based on the Non-Motor Symptoms Scale (NMSS). Among 180 PD patients, 172 patients (96.6%) had experienced at least 2 domains of concurrent non-motor symptoms. There were two types of non-motor symptom clusters (NMSCs). The first non-motor symptom cluster (NMSC1) consisted of mood, sleep/fatigue, attention/memory, urinary symptoms, and miscellaneous symptoms, while the second non-motor symptom cluster (NMSC2) consisted of perceptual problems, gastrointestinal issues, and cardiovascular symptoms. The elderly PD patients were more often categorized as experiencing NMSC2 than NMSC1. Our subgroup cluster analysis showed that PD patients with higher scoring NMS had significantly poorer QoL in both NMSC1 and NMSC2 subgroups, with subgroup-specific patterns. NMSCs also emerged differently depending on sex and the severity of PD. In conclusion, PD patients with NMS may have a specific cluster pattern of NMSC. Some NMSCs may have a negative impact on QoL. Understanding the clinical implications of NMSC in PD patients may provide better therapeutic interventions.

Introduction

Parkinson's disease (PD) is a chronic progressive neurodegenerative disorder characterized by dopaminergic neuronal loss in the substantia nigra and other brain regions [1]. Patients with PD not only experience motor symptoms including tremor, rigidity, bradykinesia, and postural instability, but also non-motor symptoms (NMSs) including anxiety, depression, sleep disturbance, and fatigue [2].

Non-motor symptoms of PD have a substantial negative impact on quality of life (QoL) [3], [4], [5], [6]. Most PD patients experience NMS and suffer from a higher frequency of NMS as the disease progresses [7]. The large-scale multicenter PRIAMO study showed that 98.6% of PD patients experienced NMS, with a mean number of 7.8 NMS per patient (range, 0–32) [8].

Previous studies of NMS in PD have focused mainly on single or isolated NMS such as dementia, mood, fatigue, sleep disturbance, and pain [9], [10], [11], [12], [13], [14]. Although this approach has led to a better understanding of each NMS, it has major limitations because most PD patients have multiple and various NMSs.

A ‘symptom cluster’ has been defined as a group of more than two symptoms that occur concurrently and are interrelated to each other; they may or may not have a common etiology [15]. Each symptom in the cluster is independent, but strongly interrelated, and one symptom can impact another symptom through its effect on a third symptom [15], [16], [17], [18].

Most studies thus far have focused on a single NMS in an attempt to identify the NMS that has the biggest impact on QoL or to assess its effect on QoL depending on its severity. However, little information is available on which NMSs form clusters, how clusters form depending on patient condition, and the impact of formed clusters on patient's QoL.

Understanding the non-motor symptom cluster of PD patients can be beneficial for the following reasons. First, it can contribute to identifying the significant symptoms that patients experience but do not report. Second, it can anticipate potential concomitant symptoms that may be manifested in the future, thereby providing effective patient management methods to be used over the course of time. Therefore, investigation of this complex effect of simultaneously occurring NMS in PD is essential for the successful management of this disease and the improvement of QoL in PD patients [19], [20]. Therefore, we investigated the comprehensive features of non-motor symptom cluster (NMSC) and their effects on QoL in PD patients.

Section snippets

Study design and patients

Descriptive cross-sectional design was used. We recruited 180 PD patients between January 1 and April 30, 2013 from Asan Medical Center, Seoul, Korea. Inclusion criteria for the present study were: (1) patients must have been diagnosed with PD based on the United Kingdom Parkinson's Disease Society Brain Bank criteria [21]; (2) 20 years of age or older; and (3) no past history of other major health problems that could potentially influence the NMS, such as active cancer and/or chronic renal

Characteristics of subjects

The demographic and clinical characteristics of the study subjects are summarized in Table 1. Of the 180 PD patients, there were 74 men and 106 women whose mean age was 62.6 ± 10.2 years (range, 28–81 years). The mean age at onset of PD was 55.6 ± 11.6 years (range, 22–80 years) and the mean disease duration was 7.2 ± 5.7 years (range, 0.5–24.0 years). The median Hoehn and Yahr stage was 2 (interquartile range, 2–3).

Characteristics of NMS

Among the 180 PD patients, 178 patients (98.8%) experienced NMS and 172 patients (96.56%)

Discussion

The present study suggests that PD patients may have a specific NMSC and NMSCs have a negative effect to their QoL. Our results have clinical implications, as we suggest that NMS of PD patients should be assessed and managed based on the clusters of complex NMS in PD.

Our results showed that the frequency of NMS in PD was 98.8%. Consistent with previous reports [8], 96.6% (n = 172) of PD patients in the study reported symptoms in at least two domains of NMS, with an average number of 5.1 per PD

Conclusions

PD patients with NMS may have a specific cluster pattern of NMSC. Some NMSCs may have a negative impact on QoL. Understanding the clinical implications of NMSC in PD patients may provide better therapeutic interventions.

Conflict of interest

The authors declare that they have no competing interests.

Acknowledgments

This paper was supported by research funds of Chonbuk National University in 2012.

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