Objectives/hypothesis: To explore how the different metrics of obesity, specifically body mass index (BMI), Mallampati, neck circumference, waist circumference, and waist-hip ratio, correlate with metrics of sleep disordered breathing (SDB), specifically the apnea/hypopnea index (AHI), and which is/are the most likely to predict and correlate with SDB.
Study design and methods: Four hundred fourteen patients presenting to the University of California San Diego Head and Neck Surgery Clinic for SDB had a sleep evaluation including a history and physical examination assessing the markers of obesity and a sleep test. Data comparing AHI with BMI, neck circumference, waist circumference, waist-hip ratio, and Mallampati were analyzed by means, standard deviations, and Pearson's correlations.
Results: The mean AHI for males was 34, and the mean AHI for females was 24. The mean age was 48 for both sexes. The mean waist circumference for males was 104 cm (41 inches) and for females 99 cm (39 inches). In males and females, waist measurement was most strongly correlated with SDB (males: r = 0.366, P = .00; females: r = 0.445, P = .00). The mean neck circumference for males and females was 43 cm (17 inches) and 38 cm (15 inches) (males: r = 0.358, P = .00; females: r = 0.38, P = .00). The mean waist-hip ratio for males and females was 0.94 and 0.87 (males: r = 0.359, P = .00; females: r = 0.254, P = .03). The mean BMI for males and females was 31 kg/m2 (males: r = 0.325, P = .00; females: r = 0.40, P = .00), and the mean Mallampati for males and females was 2.84 and 2.92 (males: r = 0.176, P = .012; females: r = 0.149, P = .16). A linear regression demonstrated that waist and neck circumference were better correlates of SDB than BMI.
Conclusion: Obesity correlates with SDB severity. Waist circumference is a better measure than BMI or neck circumference to predict SDB. Men and women are anthropometrically different. Even with an AHI of 5 or more, only half of SDB patients in this study were clinically obese. An abnormal waist circumference for men and women is 102 cm (40 inches) or more.