Is C-reactive protein a marker of obstructive sleep apnea?: A meta-analysis

Abstract

Background: Obstructive sleep apnea (OSA) is a common disease, distinguished by recurrent episodes of upper airway obstruction during sleep, with an inflammatory component. C-reactive protein (CRP) and high-sensitivity C-reactive protein (hs-CRP) are markers of systemic inflammation and may serve as biomarkers of OSA.

Methods: Scientific studies published from January 1, 2006, to January 1, 2016 were obtained via searches of PubMed, Embase, SCI, and China National Knowledge Internet (CNKI) using relevant terms. Studies concerning serum CRP level/ hs-CRP in OSA patients were reviewed by 2 independent reviewers. Studies were included if they conform with our specific criteria of inclusion. Eligible studies were subjected to quality review, data extraction, and meta-analysis by using RevMan (version 5.2) and STATA (version 12.0).

Results: There were 15 studies that met inclusion criteria that included a total of 1297 subjects. Meta-analysis revealed that serum CRP levels in the OSA group were 1.98 mmol/L higher than those in control group (95% confidence interval: 1.39-2.58, P < .01). Similarly, serum hs-CRP levels in the OSA group were 1.57 mmol/L higher than that in the control group (95% confidence interval: 0.96-2.18, P < .01). Subgroup analysis showed greater differences between OSA patients and controls in the setting of obesity (body mass index)> = 30. The total weighted mean difference (WMD) between OSA and controls within the subgroup of subjects who had a CRP was 2.10; for hs-CRP, the WMD was 2.49. Comparing OSA patients of mean apnea hypopnea index> = 15 and controls, the total WMD for the CRP subgroup was 2.19; for the hs-CRP subgroup, the WMD was 1.70.

Conclusion: In our meta-analysis, serum CRP/hs-CRP levels were discovered to be higher in OSA patients compared with control subjects. Those with higher body mass index and apnea hyponea index demonstrated larger differences in CRP/hs-CRP levels. These data are consistent with an inflammatory component of OSA pathophysiology and support the role of CRP/hs-CRP as a biomarker in this disease.

Figure 1

Flow chart of the study selection process. After careful discussion between the 2 reviewers, a total of 10 studies were included to perform the meta-analysis.

Figure 2

Comparison of CRP/hs-CRP levels between OSA group and control group in the 15 included studies. Comparison of CRP/hs-CRP levels between OSA group and control group in the 15 included studies. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI). CRP = C-reactive protein, hs-CRP = high-sensitivity C-reactive protein, OSA = obstructive sleep apnea.

Figure 3

Subgroup analysis based on BMI> = 30. Calculation based on random effects model. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI).

Figure 4

Subgroup analysis based on BMI< = 30. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI).

Figure 5

Subgroup analysis based on average AHI> = 15. Results are expressed as weighted mean difference (WMD) and 95% confidence intervals (95% CI).