Depression in Parkinson's disease: A case-control study.

BACKGROUND: To evaluate the association between Parkinson's disease (PD) prognosis and the patient's onset of depression.

METHODS: A total of 353 patients with newly-diagnosed PD and a history of depression were enrolled. On the basis of the onset of depression before or after PD diagnosis, we divided participants into PD patients with pre- or post-diagnostic depression. Cox's regression analysis was used to detect risks between the onset of depression and outcomes (including death, accidental injury, dementia, and aspiration pneumonia). The association between the onset of depression and levodopa equivalent dosage (LED) and cumulative equivalent dosage of antidepressants were assessed.

RESULTS: PD patients with post-diagnostic depression were associated with significantly higher risks of dementia (adjusted HR = 2·01, p = 0·015), and were older (58·5 ± 17·7 vs. 53·7 ± 18·6, p = 0·020) at the time of PD diagnosis than PD patients with pre-diagnostic depression. The higher incident rate of accidental injury was also noted in PD patients with post-diagnostic depression (48·1 vs. 31·3/1000 person-years, HR = 1·60, p = 0·041), but no statistical significance was observed in the adjusted hazard ratio (HR) (HR = 1·52, p = 0·069). Otherwise, mortality, motor condition and severity of depression revealed no significant difference between PD patients with pre-diagnostic and post-diagnostic depression.

CONCLUSION: PD patients with post-diagnostic depression had higher incidence of dementia, implying different onset time of depression could be associated with different subtypes and spreading routes which should be examined in follow-up studies.