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Original Research: SLEEP MEDICINE |

C-Reactive Protein Is Associated With Obstructive Sleep Apnea Independent of Visceral Obesity

Macy Mei-sze Lui, MBBS; Jamie Chung-mei Lam, MBBS, FCCP; Henry Ka-Fung Mak, MD; Aimin Xu, PhD; Clara Ooi, MD; David Chi-leung Lam, PhD, FCCP; Judith Choi-wo Mak, PhD; Pek Lan Khong, MD; Mary Sau-Man Ip, MBBS, MD, FCCP
Author and Funding Information

*From the Departments of Medicine (Drs. Lui, D. Lam, J. Lam, and J. Mak), and Diagnostic Radiology (Drs. Khong, H. Mak, and Ooi), and Research Centre of Heart, Brain, Hormone and Healthy Aging (Drs. Xu and Ip), Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.

Correspondence to: Mary Sau-Man Ip, MBBS, MD, FCCP, Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong SAR, People's Republic of China; e-mail: msmip@hkucc.hku.hk


This study is supported by a grant from Lee Wing Tat Cardiorespiratory Fund (20000575.20600.400.01) and Hong Kong Research Grants Council grant award (HKU 7582/06M).

The authors have no conflicts of interest to disclose.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).


Chest. 2009;135(4):950-956. doi:10.1378/chest.08-1798
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Background:  Obstructive sleep apnea (OSA) is associated with adverse cardiovascular outcomes. C-reactive protein (CRP) predicts atherosclerotic complications. Our study evaluates whether OSA is associated with an elevated CRP level, after elimination of known confounders including visceral obesity.

Methods:  Men without significant chronic medical illness, regular medications, or illness in the preceding 4 weeks were enrolled. Subjects with morbid obesity, newly detected high BP, or fasting glucose were excluded. They underwent polysomnography and MRI of abdomen to quantify visceral fat volume. High-sensitivity CRP levels were measured.

Results:  111 men with mean body mass index (BMI) 26.3 ± 3.8 kg/m2 were evaluated. After adjustment for age, smoking, BMI, waist circumference, and sleep efficiency, CRP correlated positively with the apnea-hypopnea index (AHI) [r = 0.35, p < 0.001], duration of O2 saturation < 90% (r = 0.29, p = 0.002), and arousal index (r = 0.32, p = 0.001), and it correlated negatively with minimal O2 saturation (r = −0.29, p = 0.002). These correlations were consistent when adjustment was made for MRI visceral fat volume instead of waist circumference. In the regression model, significant predictors of CRP included AHI, waist circumference, and triglycerides (adjusted R2, 0.33, p = 0.001, p = 0.002, p = 0.018, respectively). Among the 111 subjects, 32 subjects with no or mild OSA (AHI < 15 events/h) were matched with 32 subjects with moderate-to-severe OSA (AHI ≥ 15 events/h) in MRI visceral fat volume. CRP was higher in subjects with moderate-to-severe OSA (median, 1.32; 0.45 to 2.34 mg/L) when compared to subjects with no or mild OSA (median, 0.54; 0.25 to 0.89 mg/L; p = 0.001).

Conclusions:  In healthy middle-aged men, elevated CRP level is associated with OSA independent of visceral obesity.

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