title: Meta-analyses on prevalence of selected Parkinson's nonmotor symptoms before and after diagnosis.
abstract: BACKGROUND
  Nonmotor symptoms are common among patients with Parkinson's disease (PD) and some may precede disease diagnosis.
  
  
  METHODS
  We conducted a meta-analysis on the prevalence of selected nonmotor symptoms before and after PD diagnosis, using random-effect models. We searched PubMed (1965 through October/November 2012) for the following symptoms: hyposmia, constipation, rapid eye movement sleep behavior disorder, excessive daytime sleepiness, depression, and anxiety. Eligible studies were publications in English with original data on one or more of these symptoms.
  
  
  RESULTS
  The search generated 2,373 non-duplicated publications and 332 met the inclusion criteria, mostly (n = 320) on symptoms after PD diagnosis. For all symptoms, the prevalence was substantially higher in PD cases than in controls, each affecting over a third of the patients. Hyposmia was the most prevalent (75.5% in cases vs. 19.1% in controls), followed by constipation (50% vs. 17.7%), anxiety (39.9% vs. 19.1%), rapid eye movement sleep behavior disorder (37.0% vs. 7.0%), depression (36.6% vs. 14.9%), and excessive daytime sleepiness (33.9% vs. 10.5%). We observed substantial heterogeneities across studies and meta-regression analyses suggested that several factors might have contributed to this. However, the prevalence estimates were fairly robust in several sensitivity analyses. Only 20 studies had data on any symptoms prior to PD diagnosis, but still the analyses revealed higher prevalence in future PD cases than in controls.
  
  
  CONCLUSIONS
  These symptoms are common among PD patients both before and after diagnosis. Further studies are needed to understand the natural history of nonmotor symptoms in PD and their etiological and clinical implications.
authors: Epidemiology Branch, National Institute of Environmental Health Sciences, 111 T.W. Alexander Dr, P.O. Box 12233, Mail drop A3-05, Research Triangle Park, NC 27709 USA.
authors: Honglei
authors: H
authors: Chen
authors: Epidemiology Branch, National Institute of Environmental Health Sciences, 111 T.W. Alexander Dr, P.O. Box 12233, Mail drop A3-05, Research Triangle Park, NC 27709 USA.
authors: Edward J
authors: EJ
authors: Zhao
authors: Epidemiology Branch, National Institute of Environmental Health Sciences, 111 T.W. Alexander Dr, P.O. Box 12233, Mail drop A3-05, Research Triangle Park, NC 27709 USA.
authors: Wen
authors: W
authors: Zhang
authors: Social & Scientific Systems, Inc, Durham, North Carolina USA.
authors: Yi
authors: Y
authors: Lu
authors: Epidemiology Branch, National Institute of Environmental Health Sciences, 111 T.W. Alexander Dr, P.O. Box 12233, Mail drop A3-05, Research Triangle Park, NC 27709 USA.
authors: Rui
authors: R
authors: Liu
authors: Departments of Neurology, Radiology, Neurosurgery, Pharmacology, & Kinesiology, Pennsylvania State University-Milton S. Hershey Medical Center, Hershey, Pennsylvania USA.
authors: Xuemei
authors: X
authors: Huang
authors: Social & Scientific Systems, Inc, Durham, North Carolina USA.
authors: Anna J
authors: AJ
authors: Ciesielski-Jones
authors: Social & Scientific Systems, Inc, Durham, North Carolina USA.
authors: Michele A
authors: MA
authors: Justice
authors: Social & Scientific Systems, Inc, Durham, North Carolina USA.
authors: Deborah S
authors: DS
authors: Cousins
authors: Biostatistics Branch, National Institute of Environmental Health Sciences, Research Triangle Park, NC USA.
authors: Shyamal
authors: S
authors: Peddada
keywords: Meta-analysis; Natural history; Nonmotor symptoms; Parkinson’s disease; Prevalence