Effect of motor improvement on quality of life following subthalamic stimulation is mediated by changes in depressive symptomatology

Background/Aims: Subthalamic deep brain stimulation (STN-DBS) for Parkinson’s disease (PD) improves motor symptoms and quality of life (QOL). Because depression is a potent correlate of QOL, and STN-DBS may be associated with changes in mood, this study sought to determine whether QOL improvement is a direct or indirect consequence of motor improvement. Methods: 26 patients with PD, free of dementia and major depression, who consecutively underwent bilateral, microelectrode-guided STN-DBS, underwent preoperative and 3-month postoperative neuropsychological evaluation, including measures of QOL (PD Questionnaire –39) and depressive symptoms (Beck Depression Inventory). Results: Motor score in the Unified Parkinson’s Disease Rating Scale (UPDRS Part III) improved significantly with STN-DBS relative to preoperative ‘on’ and ‘off’ scores, as did QOL and depressive symptoms. Extent of QOL improvement tended to be associated with improvement in motor score from presurgical on to postsurgical on stimulation and on medication state. QOL improvement was significantly related to amelioration of depressive symptoms. Partial correlations revealed that the association between QOL improvement and depression remained significant when influence of motor improvement on QOL and depression was controlled for. The motor-QOL association was no longer significant when effects of depression were controlled for. Conclusions: Significant QOL improvements after STN-DBS are associated with improved motor ‘on’ state and depressive symptoms. The influence of motor improvement on QOL may be largely indirect by reducing depression.