Purpose: A close relationship between obstructive sleep apnea (OSA) and atherosclerosis has been reported, but it is still discussed controversially whether OSA affects vascular function and structure independently. Therefore, we prospectively investigated the independent impact of OSA and its treatment on arterial stiffness.
Methods: One hundred seventy-two patients with suspected OSA were prospectively enrolled in a non-randomized 6-month study to determine whether effective treatment (respiratory events sufficiently reduced and proven compliance) of OSA with continuous positive airway pressure (CPAP) would affect vascular function as measured by augmentation index (Aix) and pulse wave velocity (PWV). Additionally, using a nested case-control, we matched 45 pairs of patients with and without OSA for gender, age, and hypertension.
Results: Overall, OSA (n = 117) was associated with increased Aix (23.6 ± 13.5 vs. 8.9 ± 13.7, p < 0.001) and PWV (9.1 ± 1.6 vs. 7.8 ± 1.6 m/s, p < 0.001) as compared with that in controls without OSA (n = 55). Multivariable analysis and results from the nested case-control cohort showed that OSA was associated with increased Aix and PWV independently from hypertension, age, gender, body mass index, and antihypertensive medications. In 49 effectively treated OSA patients, Aix (baseline 22.0 ± 13.4, follow-up 20.1 ± 12.9, p < 0.01) and PWV (baseline 9.6 ± 1.5, follow-up 8.7 ± 1.4, p < 0.05) had improved. In contrast, ineffectively treated OSA patients (n = 39) showed no change in Aix and PWV.
Conclusions: This prospective controlled study suggests that OSA is independently associated with increased arterial stiffness. Furthermore, treatment with CPAP significantly reduced arterial stiffness. These findings extend our understanding of the recently shown cardiovascular burden in OSA and help to explain why CPAP treatment proved to ameliorate cardiovascular outcome even in patients without preexisting cardiovascular disease.