Background

Depression is one of the most common nonmotor symptoms associated with Parkinson's disease (PD), yet the impact of depression on progression of disease is unclear.

Objective

The aim of this study was to prospectively characterize the relationship between depressive symptoms and measures of disease progression in a large sample of patients with early, medically treated PD.

Methods

Baseline and longitudinal Beck Depression Inventory (BDI) scores from participants in the NINDS Exploratory Trials in PD Long Term Study 1 were correlated with changes in multiple measures of disease severity over 5 years. Multivariate analysis of predictors of change in BDI was performed.

Results

Of 1,741 participants, 746 completed 5-year assessments and were included. Mean age was 62.00 years (standard deviation [SD]: 9.22) and mean disease duration was 1.69 years (SD, 1.16). Mean BDI score was 6.24 (SD, 5.02) at baseline and 8.57 (SD, 6.60) at 5 years. Baseline BDI score was strongly associated with rate of change in all examined measures of disease severity. In multivariate analysis, BDI 5-year change was associated with change in UPDRS Part I (excluding depression item; P < 0.01), 33-item Parkinson's Disease Questionnaire (P < 0.01), EuroQOL Five Dimensional Questionnaire (P = 0.02), and Total Functional Capacity (P < 0.01), but was not associated with motor or cognitive measures. This model explained 68.8% of the variance 5-year change of the BDI score.

Conclusions

Worse baseline BDI scores are associated with a decline in multiple measures of disease severity in PD. Worsening of BDI at 5 years was associated with worsening in UPDRS Part I and quality-of-life measures, but not with motor or cognitive measures.