New index for analysis of polysomnography, 'integrated area of desaturation', is associated with high cardiovascular risk in patients with mild to moderate obstructive sleep apnea

Abstract

Background: Although obstructive sleep apnea (OSA) severity is evaluated by the apnea-hypopnea index (AHI), the value of AHI in evaluating cardiovascular risks, especially in mild to moderate OSA, is unclear.

Objectives: The purpose of this study is to evaluate the validity of a new index, the integrated area of desaturation (IAD), to detect the incidence of cardiovascular events (CVEs) in such patients.

Methods: We enrolled 230 consecutive patients with mild to moderate OSA and 354 with severe OSA diagnosed by polysomnography, of whom 53 and 112, respectively, had CVEs. The IAD was calculated by dividing the area of desaturation by total sleep time in polysomnography. C-reactive protein (CRP) was also measured for all patients.

Results: In the mild to moderate OSA patients, the mean IAD of the CVEs group was significantly higher than that of the non-CVE group (94.4 +/- 82.7 vs. 62.3 +/- 50.8, p = 0.001), whereas mean AHI and 3% oxygen desaturation index were similar in both groups. Multivariate analysis demonstrated that the IAD was an independent variable for CVEs (OR 1.006, 95% confidence interval 1.001-1.012, p = 0.031). Moreover, the IAD level of the high CRP group was significantly higher than that of the low CRP group (92.9 +/- 84.8 vs. 63.9 +/- 54.5, p = 0.009). There was no significant difference in AHI, IAD or other polysomnographic parameters in the severe OSA patients.

Conclusions: IAD might be superior to AHI alone in the evaluation of the history of CVEs in mild to moderate OSA patients, and it deserves attention as a possible predictor of future CVEs.