Event-Weighted Desaturation Burden and Cardiovascular Mortality in Sleep Apnoea: Findings from a Large Community-Based Prospective Cohort

Abstract

BACKGROUND AND AIMS: Obstructive sleep apnoea's prognostic value is limited by reliance on the apnoea-hypopnoea index (AHI), which fails to capture physiological heterogeneity of respiratory events. We developed a composite metric, event-weighted desaturation burden (EWDB), integrating weighted respiratory event load, regularity of consecutive inter-event intervals, and cumulative desaturation area. We evaluated its association with cardiovascular mortality and its incremental prognostic value compared with AHI and established hypoxic metrics. METHODS: We analysed 4,904 adults from the Sleep Heart Health Study with baseline polysomnography and adjudicated follow-up. EWDB was derived by combining a respiratory weighted index, a distribution factor based on inter-event interval regularity, and event-linked hypoxic burden (HB). RESULTS: The primary outcome was cardiovascular mortality. Over a median follow-up of approximately 11 years, 341 cardiovascular deaths occurred. In fully adjusted multivariable Cox models, higher EWDB was independently associated with cardiovascular mortality. However, AHI and HB associations were attenuated and lost statistical significance after full adjustment. EWDB (per 1-SD increase) remained robustly associated with cardiovascular mortality, whereas AHI did not. Incorporating EWDB into a comprehensive clinical model provided incremental risk stratification. Similar robust associations were observed for fatal coronary heart disease and incident heart failure. CONCLUSIONS: EWDB was independently associated with cardiovascular mortality and provided incremental prognostic information beyond established clinical and sleep-related factors in this cohort. By integrating respiratory event intensity, cumulative burden, and inter-event interval regularity, EWDB may better characterize cardiovascular stress related to sleep-disordered breathing.