Background: Patients with obstructive sleep apnea (OSA) have high levels of muscle sympathetic nerve activity (MSNA). We tested the hypothesis that long-term continuous positive airway pressure (CPAP) treatment will decrease MSNA in OSA patients.
Methods and results: We measured blood pressure, heart rate, and MSNA in 11 normotensive, otherwise healthy patients with OSA who were treated with CPAP. The measurements were obtained at baseline and after 1 month, 6 months, and 1 year of CPAP treatment. These measurements were compared with those recorded in 9 otherwise healthy OSA patients who were not treated with CPAP for 1 year. In both untreated and treated patients, blood pressure and heart rate did not change over time. MSNA was similar during repeated measurements in the untreated group. By contrast, MSNA decreased significantly over time in patients treated with CPAP. This decrease was evident after both 6 months and 1 year of CPAP treatment (P=0.02 for both).
Conclusions: CPAP treatment decreases muscle sympathetic traffic in patients with OSA. This effect of CPAP is evident only after an extended duration of therapy.