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Sleep-disordered Breathing and Cardiovascular Disease

An Outcome-based Definition of Hypopneas

¹ Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland; ² Center for Aging and Population Health, Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania; ³ Population Health Sciences, University of Wisconsin; ⁴ Institute for the Future of Aging Services, American Association of Homes and Services for the Aging, Washington, DC; and ⁵ Division of Pulmonary and Critical Care Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania

Correspondence and requests for reprints should be addressed to Naresh M. Punjabi, M.D., Ph.D., Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, 5501 Hopkins Bayview Circle, Baltimore, MD 21224. E-mail: npunjabi{at}jhmi.edu

Rationale: Epidemiologic studies on the consequences of sleep-disordered breathing invariably use the apnea–hypopnea index as the primary measure of disease severity. Although hypopneas constitute a majority of disordered breathing events, significant controversy remains about the best criteria used to define these events.

Objectives: The current investigation sought to assess the most appropriate definition for hypopneas that would be best correlated with cardiovascular disease.

Methods: A community sample of middle-aged and older adults was recruited as part of the Sleep Heart Health Study. Full-montage polysomnography was conducted and hypopneas were defined using different thresholds of oxyhemoglobin desaturation with and without arousals. Prevalent cardiovascular disease was assessed based on self-report. Logistic regression analysis was used to characterize the independent association between the hypopnea index and prevalent cardiovascular disease.

Measurements and Main Results: Using a sample of 6,106 adults with complete data on cardiovascular disease status and polysomnography, the current study found that hypopneas associated with an oxyhemoglobin desaturation of 4% or more were associated with prevalent cardiovascular disease independent of confounding covariates. The adjusted prevalent odds ratios for quartiles of the hypopnea index using a 4% desaturation criterion were as follows: 1.00 (<1.10 events/h), 1.10 (1.01–3.20 events/h), 1.33 (3.21–7.69 events/h), and 1.41 (>7.69 events/h). Hypopnea measures based on less than 4% oxyhemoglobin desaturation or presence of arousals showed no association with cardiovascular disease.

Conclusions: Hypopneas comprise a significant component of sleep-disordered breathing in the general community. By varying the criteria for defining hypopneas, this study demonstrates that hypopneas with a desaturation of at least 4% are independently associated with cardiovascular disease. In contrast, no association was observed between cardiovascular disease and hypopneas associated with milder desaturations or arousals.

Key Words: sleep-disordered breathing • cardiovascular disease • Sleep Heart Health Study

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Sleep-disordered breathing has been associated with numerous health consequences. However, empirical data on an outcome-based definition of hypopneas are lacking. What This Study Adds to the Field Hypopneas with a 4% or more decrease in oxyhemoglobin saturation are associated with prevalent cardiovascular disease. Hypopneas with less than a 4% desaturation or those with an arousal are not associated with prevalent cardiovascular disease.