Parkinson’s disease (PD) is characterized by a high prevalence of (non)-motor symptoms. Subthalamic Nucleus Deep Brain Stimulation (STN-DBS) is a common treatment for advanced PD as it reduces symptoms and improves Quality of Life (QoL). However, previous studies indicated that apathy could arise after STN-DBS and may worsen QoL outcomes. This study examined to what extent changes in apathy and depression were associated with changes in QoL following STN-DBS in people with PD and explored whether age and sex were associated with changes in apathy and QoL.

The sample consisted of 212 people with PD (Mage = 66.19, SDage = 8.37; 62.74% males). Self-report questionnaires were used to evaluate apathy, QoL and depression before and after STN-DBS. Change scores were computed, and associations were examined using Pearson correlations and hierarchical multiple linear regression. On average, apathy increased, whereas depression decreased and QoL improved following STN-DBS. Increases in apathy were associated with worsening in QoL, whereas improvement in depression was associated with improvement in QoL. 

However, in the regression model including apathy and controlling for baseline QoL, age and sex, only changes in depression, higher baseline QoL and older age predicted greater deterioration in QoL. Exploratory analyses indicated that men exhibited a greater increase in apathy than women, and that older age, was associated with worsening in QoL. These findings suggest that following STN-DBS, changes in depression and age may influence changes in QoL more strongly than apathy does. Although, future research should still consider apathy in QoL outcomes.