Objectives: Obstructive Sleep apne syndrome is a disease with high morbidity and mortality. The aim of this study was to investigate the conditions affecting the mortality of patients diagnosed with OSAS at six year follow up. Methods: 970 patients who admitted to Sleep laboratory between 2011-2013 were evaluated retrospectively. 74 patients whose mortality data could not be accessed through the system were excluded. The patients who died until April 2019 were compared with the surviving group in terms of demographic, clinical, comorbidities and polysomnographic findings. Results: Total 47 patients who died were older, had higher BMI, AHI and ODI values, lower minimum oxygen saturations compared with the survival group (p < .001). In the Cox-hazard regression analysis, BMI (hazard ratio (HR), 1.08; 95% CI, 1.04-1.12), age (1.12, 1.08-1.15), accompanying COPD (2.19, 1.08-4.43), accompanying CAD (2.76, 1.34-5.67) and AHI of >50/h (2.19, 1.19-1.4.05) were reported. Conclusion: This study showed that OSAS increases the risk of death accompanied by CAD and COPD. It has also been shown that patients with higher AHI (AHI > 50/h) values die more. Therefore, it may be useful to classify the AHI> 50/h group as very severe OSAS instead of severe OSAS.