Impact of different hypopnea definitions on obstructive sleep apnea severity and cardiovascular mortality risk in women and elderly individuals

Abstract

ObjectiveTo assess the impact of three hypopnea definitions on the severity classification of obstructive sleep apnea (OSA) and its association with cardiovascular mortality risk in women and elderly individuals. MethodsWe analyzed two Spanish clinical cohorts (1116 women and 939 elderly individuals) who were studied for suspicion of OSA between 1998 and 2007. A calibration model was used to apply different definitions of hypopnea to our two cohorts. Hypopnea was defined as a 30–90% reduction in oronasal flow for ≥10 s followed by (1) ≥4% fall in oxyhemoglobin saturation—AHI4%; (2) ≥3% fall in oxyhemoglobin saturation—AHI3%; or (3) ≥3% fall in oxyhemoglobin saturation or an event-related arousal—AHI3%a. ResultsIn both cohorts, the prevalence of an AHI ≥30 events/h increased by 14% with AHI3%a, compared to AHI4% criteria. The percentage of women with an AHI <5 events/h decreased from 13.9% with AHI4% to 1.1% with the AHI3%a definition. In fully adjusted multivariable analyses, AHI ≥30 events/h was associated with increased cardiovascular mortality risk in women, regardless of the hypopnea definition, and in elderly individuals diagnosed using the AHI4% and AHI3% but not the AHI3%a definition. ConclusionsOur findings suggest that hypopnea definitions substantially influence OSA prevalence and severity classification, and also affect the association with cardiovascular outcomes. With the currently recommended criterion (AHI3%a), a threshold of 30 events/h is appropriate to identify women, but not elderly individuals with increased risk of cardiovascular death.