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The Impact of Obesity on Oxygen Desaturation during Sleep-disordered Breathing

¹ Department of Population Health Sciences, University of Wisconsin-Madison, Madison, Wisconsin; and ² Clinical and Academic Unit of Sleep and Breathing, National Heart and Lung Institute, Imperial College London, Royal Brompton Hospital, London, United Kingdom

Correspondence and requests for reprints should be addressed to Paul E. Peppard, Ph.D., Department of Population Health Sciences, University of Wisconsin-Madison, WARF Building #685, 610 Walnut St., Madison, WI 53726. E-mail: ppeppard{at}wisc.edu

Rationale: Obesity increases the risk and severity of sleep-disordered breathing. The degree to which excess body weight contributes to blood oxygen desaturation during hypopneic and apneic events has not been comprehensively characterized.

Objectives: To quantify the association between excess body weight and oxygen desaturation during sleep-disordered breathing.

Methods: A total of 750 adult participants in the Wisconsin Sleep Cohort Study were assessed for body mass index (BMI) (kg/m²) and sleep-disordered breathing. The amount of Sa_O2, duration, and other characteristics of 37,473 observed breathing events were measured during polysomnography studies. A mixed-effects linear regression model estimated the association of blood oxygen desaturation with participant-level characteristics, including BMI, gender, and age, and event-level characteristics, including baseline Sa_O2, change in VT, event duration, sleep state, and body position.

Measurements and Main Results: BMI was positively associated with oxygen desaturation severity independent of age, gender, sleeping position, baseline Sa_O2, and event duration. BMI interacted with sleep state such that BMI predicted greater desaturation in rapid eye movement (REM) sleep than in non-REM sleep. Each increment of 10 kg/m² BMI predicted a 1.0% (SE, 0.2%) greater mean blood oxygen desaturation for persons in REM sleep experiencing hypopnea events associated with 80% VT reductions.

Conclusions: Excess body weight is an important predictor of the severity of blood oxygen desaturation during apnea and hypopnea events, potentially exacerbating the impact of sleep-disordered breathing in obese patients.

Key Words: sleep apnea • overweight • hypoxia

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject Obesity increases the risk of sleep-disordered breathing, but the extent to which excess body weight influences the amount of blood oxygen desaturation during apneic and hypopneic events has not been characterized. What this Study Adds to the Field We show that body mass index is a significant independent predictor of the amount of oxygen desaturation during apneas and hypopneas. The impact of sleep disordered breathing may be greater in obesity due to exacerbation of intermittent hypoxia.