Impact of obstructive sleep apnea and comorbid insomnia on all-cause mortality: a prospective cohort study of 2401 patients with 6-year follow-up

Abstract Study Objectives The impact of obstructive sleep apnea (OSA) on all-cause mortality needs further research as earlier data are inconclusive. Between 30 and 50% of patients with OSA have comorbid insomnia (COMISA), which may increase the risk of morbidity and mortality. The present study was aimed at investigating the association between OSA and COMISA and the subsequent risk of all-cause mortality in a cohort of patients recruited from a hospital sleep clinic setting. Methods Between January 2016 and December 2018, 2401 patients with suspected OSA underwent standard respiratory polygraphy and were recruited in the present analysis. OSA was categorized according to the respiratory event index (REI). Insomnia diagnosis was assessed with the Bergen Insomnia Scale. All-cause mortality was the primary endpoint. Results Mean age was 49.6 ± 14.0 years, 68.8% were males, and 36.2% had OSA with REI ≥ 15, 49.5% insomnia, and 16.9% COMISA (comorbid insomnia and OSA with REI ≥ 15). A progressive increase in the risk of all-cause mortality was observed with increasing OSA severity (REI < 5; 5–14.9; 15–29.9; ≥ 30). In a multivariable Cox regression analysis, OSA (REI ≥ 15) was independently associated with all-cause mortality (HR 2.65; 95% CI 1.12–6.30, p = 0.027). This relative risk was further increased to threefold (HR 3.02; 95% CI 1.30–7.04, p = 0.010) when OSA was replaced by COMISA in the same model. Conclusion This study demonstrates that OSA severity is an important determinant of long-term survival. Patients with moderate-to-severe OSA are at particularly increased risk, and the coexistence of insomnia appears to substantially amplify this risk. These findings underscore the prognostic significance of considering both sleep-disordered breathing and comorbid insomnia when assessing mortality risk in patients evaluated for OSA. Brief summary Obstructive sleep apnea (OSA) is linked to cardiovascular disease, but its impact on mortality, especially when combined with insomnia (COMISA), remains underexplored. This study investigated the prognostic OSA severity and COMISA in a large cohort of 2401 patients with suspected OSA. Our findings showed that moderate to severe OSA significantly predicted all-cause mortality, independent of traditional risk factors. The presence of COMISA tripled this risk, highlighting a synergistic negative effect. These results emphasize the importance of recognizing COMISA as a distinct, high-risk phenotype. Future clinical practice should include systematic screening and treatment of both OSA and insomnia to improve survival outcomes in affected patients.