Composition of nocturnal hypoxaemic burden and its prognostic value for cardiovascular mortality in older community-dwelling men

Aims To investigate the composition of nocturnal hypoxaemic burden and its prognostic value for cardiovascular (CV) mortality in community-dwelling older men. Methods and results We analysed overnight oximetry data from polysomnograms obtained in 2840 men from the Outcomes of Sleep Disorders in Older Men (MrOS Sleep) study (ClinicalTrials.gov Identifier: NCT00070681) to determine the number of acute episodic desaturations per hour (oxygen desaturation index, ODI) and time spent below 90% oxygen saturation (T90) attributed to acute desaturations (T90desaturation) and to non-specific drifts in oxygen saturation (T90non-specific), respectively, and their relationship with CV mortality. After 8.8 +/- 2.7 years follow-up, 185 men (6.5%) died from CV disease. T90 [hazard ratio (HR) 1.21, P< 0.001], but not ODI (HR 1.13, P= 0.06), was significantly associated with CV death in univariate analysis. T90 remained significant when adjusting for potential confounders (HR 1.16, P= 0.004). Men with T90> 12 min were at an elevated risk of CV mortality (HR 1.59; P= 0.006). Approximately 20.7 (5.7-48.5) percent of the variation in T90 could be attributed to non-specific drifts in oxygen saturation. T90desaturation and T90non-specific were individually associated with CV death but combining both variables did not improve the prediction. Conclusion In community-dwelling older men, T90 is an independent predictor of CV mortality. T90 is not only a consequence of frank desaturations, but also reflects non-specific drifts in oxygen saturation, both contributing towards the association with CV death. Whether T90 can be used as a risk marker in the clinical setting and whether its reduction may constitute a treatment target warrants further study.