Obstructive: Sleep Apnea Syndrome (OSAS) is a condition marked by recurrent interruptions in airflow during sleep, causing intermittent hypoxia and inflammation. These changes adversely affect neurocognitive functions. OSAS is linked to impairments in executive functions, memory, attention, and intellectual capacity. This study aims to evaluate the effects of OSAS on cognitive functions and inflammatory markers and the impact of Continuous Positive Airway Pressure (CPAP) treatment. Methods: This retrospective study included 106 OSAS patients and 49 healthy controls, classified based on their Apnea-Hypopnea Index (AHI) and CPAP treatment adherence. Patients in the treatment group used CPAP for at least 4 hours daily over 3 months. Cognitive performance was measured using the Montreal Cognitive Assessment, and inflammatory markers such as Platelet Distribution Width (PDW), Platelet-Lymphocyte Ratio (PLR), and Neutrophil-Lymphocyte Ratio (NLR) were analyzed. Results: MoCA scores showed significant declines in cognitive functions across all OSAS groups (p < 0.001), with notable reductions in executive functions, language, and abstraction. Treated patients showed higher cognitive scores, though differences were not statistically significant. PDW, PLR, and NLR levels were significantly lower in the CPAP-treated group compared to untreated patients. Conclusion: Untreated OSAS significantly affects cognitive functions, particularly executive functions, language, and abstraction. CPAP treatment provides partial cognitive improvement and reduces inflammatory markers like PLR, PDW, and NLR. These markers may be valuable in assessing treatment effects and detecting suspected OSAS. Further research with larger cohorts is needed to validate these findings and enhance clinical management.