Conventional metrics to evaluate sleep disordered breathing (SDB) have many limitations including their inability to identify subclinical markers of cardiovascular (CV) dysfunction.Does sleep study-derived circulation time (Ct) predict mortality, independent of CV risks and SDB severity?We derived average lung to finger Ct (LFCT) from sleep studies in older men enrolled in the multi-center Outcomes of Sleep Disorders in Older Men (MrOS Sleep) study. LFCT was defined as the average time between end of scored respiratory events and nadir oxygen desaturations associated with those events. We calculated the hazards ratio (HR) for the CV and all-cause mortality by LFCT quartiles adjusting for the demographic, body habitus, baseline CV risk and disease (CVD). Additional model included apnea-hypopnea index (AHI), time with SpO2 below 90%, and hypoxic burden. We also repeated analyses after excluding those with CVD at baseline.A total of 2631 men (mean age 76.4 +- 5.5 years) were included in this study. LFCT median [IQR] was 18 [15-22] s. During average follow up of 9.9 +/- 3.5 years, 427 (16%) and 1205 (46%) men experienced CV death and all-cause death, respectively. In multivariate analysis, men in the 4th quartile of LFCT (22-52 s) had a HR of 1.36 [95% CI =1.02, 1.81] and of 1.35 [1.14, 1.60] for CV and all-cause mortality, respectively, when compared to men in the 1st quartile (4-15 s). The results were similar when additionally adjusting for AHI, time with SpO2 below 90%, or hypoxic burden. Results were stronger among men with no history of CVD at baseline.LFCT is associated with both CV and all-cause mortality in older men, independent of baseline CV burden and SDB metrics. LFCT may be a novel physiologic marker for CV vulnerability and adverse outcomes in patients with SDB.