title: Baseline predictors of worsening apathy in Parkinson's disease: A prospective longitudinal study.
abstract: BACKGROUND
  Apathy is one of the most common behavioural disorders in Parkinson's disease (PD) and contributes significantly to a reduced quality of life in PD patients.
  
  
  METHODS
  We conducted a prospective longitudinal study of 89 mild PD patients over 18 months, measuring apathy symptoms at 6-monthly intervals using the Starkstein Apathy Scale, as well as measures of motor and non-motor symptoms, cognitive function, and functional disability at baseline. Mixed-effects models were used to characterise the individual trajectories of apathy symptom severity, and linear regression with stepwise elimination procedure was used to select significant baseline predictors.
  
  
  RESULTS
  Clinically significant levels of apathy were present in 42.7% of our sample at baseline, with symptom severity remaining relatively stable on average over the course of 18 months. Male gender, lower educational attainment, higher depression symptom severity, more severe functional disability, and the presence of dyskinesias at study entry predicted increasing apathy over the subsequent 18 months.
  
  
  CONCLUSIONS
  Patients with these factors are at risk for progression of apathy, which may be prevented by treating depression and functional disability. Further studies are needed to address both the specific neurobiological pathways and psychosocial factors underpinning apathy in PD.
authors.affiliation: Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore.
authors.forename: Natalie
authors.initials: N
authors.lastname: Wee
authors.affiliation: Department of Neurology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore; Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore.
authors.forename: Nagaendran
authors.initials: N
authors.lastname: Kandiah
authors.affiliation: Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore.
authors.forename: Sanchalika
authors.initials: S
authors.lastname: Acharyya
authors.affiliation: Department of Neurology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Chander
authors.affiliation: Department of Neurology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
authors.forename: Aloysius
authors.initials: A
authors.lastname: Ng
authors.affiliation: Department of Neurology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore; Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore.
authors.forename: Wing Lok
authors.initials: WL
authors.lastname: Au
authors.affiliation: Department of Neurology, National Neuroscience Institute, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore; Duke-NUS Graduate Medical School, 8 College Road, Singapore 169857, Singapore. Electronic address: louis_tan@nni.com.sg.
authors.forename: Louis C S
authors.initials: LC
authors.lastname: Tan
mesh_terms: D000368:Aged; D057565:Apathy; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications* / Q000523:psychology*; D011446:Prospective Studies; D011569:Psychiatric Status Rating Scales; D011788:Quality of Life / Q000523:psychology; D012307:Risk Factors
keywords: Apathy; Longitudinal; Mixed-effects models; Non-motor; Parkinson's disease