Sleep architecture impairment and cognitive performance in obstructive sleep apnea phenotypes and the effects of CPAP treatment

BACKGROUND: This review investigated the impact of Obstructive Sleep Apnea (OSA) on sleep architecture and cognition. METHODS: Fifty-six entries identified from more than 11,000 records were synthesized into five sections: sleep macroarchitecture, sleep microstructure, comorbid insomnia and sleep apnea (COMISA), REM-related OSA (REM-OSA), and Continuous Positive Airway Pressure (CPAP) treatment. RESULTS: A shift toward lighter sleep and reduced Slow-Wave and REM sleep were associated with deficits in attention, memory, and executive functions. Severe OSA patients reported subjective cognitive complaints despite normal objective screening scores, highlighting a critical window for early assessment. Specific high-risk phenotypes emerged: COMISA, characterized by hyperarousal and reduced total sleep time; and REM-OSA, associated with poorer verbal memory and cognitive vulnerability in APOE ε4 carriers. Neuroimaging studies showed hippocampal disconnection and Default Mode Network dysregulation linked to REM deprivation and hypoxia-related white matter abnormalities. CPAP treatment was associated with improvements in sleep architecture and cognitive performance, although recovery appears incomplete and variable across individuals. CONCLUSION: Polysomnography-based assessment provides clinically relevant information beyond the apnea-hypopnea index, helping identify OSA patients at greatest risk of cognitive impairment. CPAP is associated with partial restoration of sleep architecture and improvement in selected cognitive domains, reinforcing the importance of sustained treatment adherence.