A prospective cohort study of the long-term effects of CPAP on carotid artery intima-media thickness in obstructive sleep apnea syndrome

Abstract

Objective: To examine the long-term effect of CPAP on carotid artery intima-media thickness (IMT) in patients with Obstructive sleep apnea syndrome(OSAS).

Methods: A prospective observational study over 12 months at a teaching hospital on 50 patients newly diagnosed with OSAS who received CPAP or conservative treatment (CT). Carotid IMT was assessed with B-mode Doppler ultrasound from both carotid arteries using images of the far wall of the distal 10 mm of the common carotid arteries at baseline, 6 months and 12 months. MEASUREMENTS AND RESULTS [MEAN (SE)]: Altogether 28 and 22 patients received CPAP and CT respectively without significant differences in age 48.8(1.8) vs 50.5(2.0)yrs, BMI 28.2(0.7) vs 28.0(1.2)kg/m2, ESS 13.1(0.7) vs 12.7(0.6), AHI 38(3) vs 39(3)/hr, arousal index 29(2) vs 29(2)/hr, minimum SaO2 75(2) vs 77(2)% and existing co-morbidities. CPAP usage was 4.6(0.3) and 4.7(0.4)hrs/night over 6 months and 1 year respectively. Carotid artery IMT at baseline, 6 months, and 12 months were 758(30), 721(20), and 705(20)micron for the CPAP group versus 760(30), 770(30), and 778(30)micron respectively for the CT group, p = 0.002. Among those free of cardiovascular disease(n = 24), the carotid artery IMT at baseline, 6 months and 12 months were 722(40), 691(40), and 659(30)micron for the CPAP group (n = 12) with usage 4.5(0.7) and 4.7(0.7) hrs/night over 6 months and 12 months whereas the IMT data for the CT group(n = 12) were 660(20), 685(10), and 690(20)micron respectively, p = 0.006.

Conclusions: Reduction of carotid artery IMT occurred mostly in the first 6 months and was sustained at 12 months in patients with reasonable CPAP compliance.

Figure 1

Patient profile. Among the 20 eligible patients who did not consent for the study, 14 had started CPAP treatment at home whereas 6 were subsequently referred for treatment with the mandibular advancement device. Among the 30 patients who had agreed to join the study initially, 22 were started on home CPAP whereas the other 8 opted for conservative treatment. However these 30 patients were unable to return for serial measurements of carotid IMT due to their busy work schedule.

Figure 2

Shows the data plots of OSA patients on CPAP (n = 28) and those on conservative treatment (n = 22). The serial mean carotid artery IMT at baseline, 6 months and 12 months were 757.5(30), 720.9(20) and 704.5(20)micron for the CPAP group versus 760.0(30), 769.8(30), and 777.7(30)micron respectively for those on conservative treatment, p = 0.002 (ANOVA for repeated measures).

Figure 3

Shows the data plots of OSA patients free of existing cardiovascular diseases (excluding smoking and alcohol consumption). The mean carotid artery IMT at baseline, 6 months and 12 months were 721.7(40), 690.8(40) and 659.2(30) micron for the CPAP group (n = 12) versus 660.0(20), 684.6(10) and 690.0(20)micron respectively for those on conservative treatment (n = 12), p = 0.006 (ANOVA for repeated measures).