AIM: We aimed to evaluate the effect of continuous positive airway pressure (CPAP) therapy on blood pressure (BP) and arterial stiffness in hypertensive patients with obstructive sleep apnea (OSA).PATIENTS AND METHODS: We studied 38 hypertensive patients who suffered from severe OSA. Ambulatory BP measurement was performed at baseline and after at least 3 months of uninterrupted CPAP therapy. In 19 of these patients, we also measured pulse wave velocity (PWV) at baseline, after the first night of CPAP therapy and at 3 months. Fifteen normotensive subjects without OSA comprised the control group.RESULTS: CPAP therapy reduced systolic BP from 141.5 ± 12.1 to 133.5 ± 9.7 mmHg (p = 0.007) and diastolic BP from 87.8 ± 6.8 to 83 ± 5.4 mmHg (p = 0.004). CPAP also reduced the PWV from 8.81 ± 1.4 to 8.18 ± 1 m/s after the first night of CPAP therapy (p = 0.003) and to 7.37 ± 1 m/s at 3 months (p = 0.007).CONCLUSIONS: To the best of our knowledge, this is the first study demonstrating that CPAP therapy in hypertensive patients with OSA improves arterial stiffness from the first night and that this favorable effect is maintained for at least 3 months of CPAP use. A reduction in BP was also observed, even though BP control was not always achieved.