The Relevance of Sleep Quality for Clinical Care in Parkinson’s Disease: Clinical and Cognitive Differences Between Good and Poor Sleepers: A Cross-Sectional Study

Background/Objectives: This study aimed to compare disease severity and cognitive performance between Parkinson’s disease (PD) patients with good and poor sleep quality. Methods: This cross-sectional observational study included 69 patients with PD. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Participants were classified as having good sleep quality (PSQI ≤ 5; n = 32) or poor sleep quality (PSQI > 5; n = 37). Disease severity was evaluated using the Unified Parkinson’s Disease Rating Scale (UPDRS) and Modified Hoehn and Yahr Scale (mH&Y). Global cognition, executive functions, and visuospatial performance were assessed using the Montreal Cognitive Assessment (MoCA), Stroop Test TBAG Form, and Clock Drawing Test, respectively. Results: Patients with poor sleep quality had significantly higher UPDRS scores (p = 0.004), longer disease duration (p = 0.043), and more advanced mH&Y (p < 0.001). They also demonstrated lower MoCA scores (p = 0.039) and lower Clock Drawing Test scores (p = 0.019). In addition, completion times on all Stroop test cards were significantly longer in the poor sleep quality group (p = 0.011–0.042), indicating poorer attention–executive performance. Moderate effect sizes were observed for disease severity and cognitive outcomes. Conclusions: Poor sleep quality was associated with greater disease severity and lower cognitive performance in early-to-mid-stage PD patients who were largely cognitively preserved. Routine assessment of subjective sleep quality may help identify patients with a higher clinical and cognitive burden and support more individualized, person-centered healthcare strategies in PD.