Comorbid Insomnia and Sleep Apnea Mechanistic Convergence, Phenotypic Heterogeneity, and Clinical Implications.

Purpose of Review: Comorbid insomnia and obstructive sleep apnea (COMISA) is increasingly viewed as more than two coexisting sleep disorders. This review asks whether COMISA reflects a distinct phenotype driven by mechanistic convergence, how heterogeneous it is across patients, and what that means for diagnosis and treatment. Recent Findings: Recent studies show COMISA is common, linked to greater sleep fragmentation, and higher cardiometabolic and psychiatric burden than either disorder alone. Mechanistic work supports bidirectional interaction between ventilatory instability and chronic hyperarousal, with autonomic and EEG findings suggesting persistent sympathetic activation and cortical hyperactivation. Treatment studies indicate that PAP and CBT-I each help, but single-modality treatment often leaves residual symptoms; combined, phenotype-informed care appears more effective. Summary: The evidence supports COMISA as a clinically important, heterogeneous convergence phenotype rather than a simple comorbidity. Future research should prioritize longitudinal outcomes, biomarker-based phenotyping, and endotype-stratified trials. This shift could move COMISA care toward more precise, mechanism-guided management.