Change in cardio-ankle vascular index by long-term continuous positive airway pressure therapy for obstructive sleep apnea

Background: It has been reported that patients with obstructive sleep apnea (OSA) have an elevated arterial stiffness, and alleviation of OSA by continuous positive airway pressure (CPAP) might attenuate this. Recently, the cardio-ankle vascular index (CAVI) has been reported to be a highly reproducible arterial stiffness parameter in OSA patients. However, the change in CAVI that occurs following long-term CPAP treatment for OSA remains unclear. Methods: Patients with moderate-to-severe OSA were enrolled. Changes in CAVI at 1 and 12 months after CPAP initiation (Delta CAVI(1) and Delta CAVI(12), respectively) were assessed. Factors associated with Delta CAVI(1) and Delta CAVI(12) were determined by multivariable regression analyses. Results: Thirty subjects were assessed. CAVI was significantly reduced at 1 month compared with the baseline from 7.80 +/- 1.19 to 7.56 +/- 1.08 (p = 0.013). A non-significant reduction was observed at 12 months (7.72 +/- 1.18, p = 0.365 versus baseline) and CAVI had actually increased compared with that measured at 1 month. In multivariable analyses, Delta CAVI(1) was inversely correlated with CPAP usage (coefficient: -0.500, p = 0.006) and was directly correlated with the change in the ratio of low frequency to high frequency in heart rate variability (coefficient: 0.607, p < 0.001), whereas Delta CAVI(12) was related to the use of angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin-II-receptor blockers (ARB; coefficient: 0.464, p = 0.013), was directly correlated with the change in hemoglobin A1c levels (coefficient: 0.644, p < 0.001), and was inversely correlated with the change in CPAP usage (coefficient: -0.380, p = 0.046). Conclusions: CAVI was significantly reduced by short-term CPAP and then slightly increased from 1 to 12 months, which was probably due to natural progression associated with the aging process. However, long-term CPAP treatment had the beneficial effect of maintaining CAVI below baseline levels when associated with the use of ACE-I/ARB, the control of blood glucose and the CPAP compliance. (C) 2011 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.