Objective: To determine the prevalence of depression, evaluate the relationship between depression, apathy and fatigue, and the impact of STN DBS on the same symptoms.

Background: The prevalence of depression in PD varies from 4 to 70%, that of apathy is about 60% and that of fatigue is 58%. Apathy often coexists with depression, but can also exist independently. Apathy is thought to be related to a dysfunction of the gratification/motivation system. The impact of STN DBS on depression, apathy and fatigue is controversial.

Methods: Patients with probable PD were selected. Validated self-questionnaires for PD on depression (Beck II), apathy and fatigue were used. Patients were segregated according to cut off scores as being symptomatic or not and according to DBS status. DBS and non-DBS patients were matched according to disease duration. Comparisons were made using Mann-Whitney-U test.

Results: Out of 297 contacted patients, 50 completed the three questionnaires and 87 at least the depression questionnaire. The population mean age was 67.0 ± 7.93 years. 21 patients (disease duration 16.05 ± 4.7 years) had had DBS and 12 (13.4 ± 4.7) not. 48% of the 87 participants had a score of at least 14 on the Beck II (depressed). Half of them were already treated with anti-depressants. 47% were not depressed but on antidepressants and the remaining 5% were not depressed and on no anti-depressant. Depressed patients had significantly more apathy (p<0.0001) and fatigue (p<0.0001) than non depressed patients. Apathetic patients had more depression (p=0.0002) and more fatigue (p=0.0021); and patients with fatigue had more apathy (p<0.0001) and depression (p=0.0064). There was no difference in depression and fatigue between STN DBS and non STN DBS patients, but operated patients had more apathy (p=0.0094).

Conclusions: In our study, only 5% are likely not to have experienced depression. Depression is under diagnosed and under treated as half of depressed patients are not treated and half is depressed in spite of anti-depressant therapy. Depression, apathy and fatigue are closely interconnected. Nevertheless, STN DBS is only associated to an increase in apathy. This supports the specificity of this symptom against fatigue and depression, and suggests that the STN may be important in the gratification/motivation system. Results from this study need to be interpreted with caution as the n is small and because of its retrospective nature.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/depression-apathy-fatigue-in-parkinson-with-or-without-stn-dbs/