The longitudinal impact of depression on disability in Parkinson disease.
OBJECTIVE
Depression in Parkinson disease (PD) is a common problem that worsens quality of life and causes disability. However, little is known about the longitudinal impact of depression on disability in PD. This study examined the association between disability and DSM-IV-TR depression status across six years.


METHODS
Longitudinal cohort study with assessments at study entry, year two, four, and six conducted in the Morris K. Udall Parkinson Disease Research Center. Recruitment totaled 137 adult men and women with idiopathic PD in which up to six years of data on demographic, motor, and non-motor variables was collected. Movement disorder specialists used the structured interview for DSM-IV-TR depressive disorders and the Northwestern Disability Scale to assess depression and disability. A generalized linear mixed model was fitted with Northwestern Disability Scale score as the dependent variable to determine the effect of baseline depression status on disability.


RESULTS
A total of 43 participants were depressed at baseline compared to 94 without depression. Depressed participants were more likely to be female, were less educated, were less likely to take dopamine agonists, and more likely to have motor fluctuations. Controlling for these variables, symptomatic depression predicted greater disability compared to both never depressed (p = 0.0133) and remitted depression (p = 0.0009). Disability associated with symptomatic depression at baseline was greater over the entire six-year period compared to participants with remitted depressive episodes or who were never depressed.


CONCLUSIONS
Persisting depression is associated with a long-term adverse impact on daily functioning in PD. Adequate treatment or spontaneous remission of depression improves ADL function.
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.|The Morris K. Udall Parkinson's Disease Research Center of Excellence, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Gregory M
GM
Pontone
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.|The Morris K. Udall Parkinson's Disease Research Center of Excellence, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Catherine C
CC
Bakker
Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Shaojie
S
Chen
The Morris K. Udall Parkinson's Disease Research Center of Excellence, Johns Hopkins University School of Medicine, Baltimore, MD, USA.|Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Zoltan
Z
Mari
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.|The Morris K. Udall Parkinson's Disease Research Center of Excellence, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Laura
L
Marsh
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.|The Morris K. Udall Parkinson's Disease Research Center of Excellence, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Peter V
PV
Rabins
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
James R
JR
Williams
Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.|The Morris K. Udall Parkinson's Disease Research Center of Excellence, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Susan S
SS
Bassett
D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003866:Depressive Disorder / Q000150:complications*; D004185:Disability Evaluation; D006233:Persons with Disabilities / Q000523:psychology*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications / Q000503:physiopathology / Q000523:psychology*; D011788:Quality of Life; D012307:Risk Factors; D012720:Severity of Illness Index
Parkinson disease; depression; disability; longitudinal; nonmotor