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

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. (C) 2014 Elsevier B.V. All rights reserved.