title: Latent growth-curve analysis reveals that worsening Parkinson's disease quality of life is driven by depression.
abstract: OBJECTIVE
  Parkinson's disease (PD) is a neurodegenerative disorder resulting in a wide variety of symptoms. The current study examined the influence of apathy, depression and motor symptoms on quality of life (QoL) in PD patients. Information was drawn from an 18-month period.
  
  
  METHODS
  Participants (N = 397) were assessed for apathy (Apathy Scale; Starkstein et al., 1992), depression (Beck Depression Inventory-II; Beck, Steer, Ball & Ranieri, 1996), motor severity (Unified Parkinson's Disease Rating Scale, Part III; UPDRS; Fahn, Elton & Committee, 1987), and QoL (Parkinson's Disease Questionnaire-39; Jenkinson, Fitzpatrick, Peto, Greenhall, & Hyman,1997) at 3 time points: an initial clinical evaluation (baseline), a 6-month follow-up, and an 18-month follow-up. Latent growth-curve models were used to determine the influence of apathy, depression, and motor symptoms on QoL trajectories.
  
  
  RESULTS
  Greater difficulties with QoL at baseline showed the strongest relationship to more severe depression symptoms, followed by more severe motor symptoms, younger age, and less education (all p values < .001). Worsening of QoL over the 18-month period was only predicted by a worsening of depression (p = .003). The relationship between QoL and depression symptoms remained significant in a subsample of nondepressed PD patients.
  
  
  CONCLUSIONS
  Overall, findings from the current study suggest that self-reported QoL among PD patients is primarily related to depression. Future efforts to improving clinical care of PD patients may benefit by focusing on improving psychosocial adjustment or treatments targeting depression.
authors.affiliation: Department of Clinical and Health Psychology, McKnight Brain Institute, University of Florida.
authors.forename: Jacob D
authors.initials: JD
authors.lastname: Jones
authors.affiliation: Department of Clinical and Health Psychology, University of Florida.
authors.forename: Michael
authors.initials: M
authors.lastname: Marsiske
authors.affiliation: Department of Neurology, McKnight Brain Institute, University of Florida.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Okun
authors.affiliation: Department of Clinical and Health Psychology, McKnight Brain Institute, University of Florida.
authors.forename: Dawn
authors.initials: D
authors.lastname: Bowers
mesh_terms: D000367:Age Factors; D000368:Aged; D057565:Apathy; D003627:Data Interpretation, Statistical; D003863:Depression / Q000523:psychology*; D018450:Disease Progression; D004522:Educational Status; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D009069:Movement Disorders / Q000209:etiology / Q000523:psychology; D010300:Parkinson Disease / Q000523:psychology*; D011569:Psychiatric Status Rating Scales; D011788:Quality of Life / Q000523:psychology*