Objectives: Although continuous positive airway pressure (CPAP) effectively prevents sleep apnea and reduces blood pressure, many patients do not use CPAP every night. This trial investigates cardiovascular effects after sleeping five nights without CPAP.

Methods: We randomized 100 patients (67 men and 33 women with a mean age 64±9 years) using CPAP treatment for moderate-to-severe sleep apnea to either withdraw treatment for five nights (n=50) or to continue with CPAP (n=50). The primary outcomes were arterial stiffness and 24h blood pressure.

Results: The 24h SBP increased by a mean of 2.8mmHg [95% confidence interval (CI) 0.2-5.4mmHg] (P=0.035) and DBP increased by a mean of 1.7mmHg (95% CI 0.1-3.3mmHg) (P=0.032) in the group without CPAP compared to the CPAP group. There was a significant effect on blood pressure in women but not in men. In women, SBP increased by 5.1mmHg (95% CI 1.0-9.5mmHg) (P=0.017) and DBP by 2.9mmHg (95% CI 0.4-5.6mmHg) (P=0.029). Arterial stiffness remained unaffected. Secondary outcomes that worsened in patients without CPAP included apnea-hypopnea index, oxygen desaturation index, hemoglobin levels, and daytime sleepiness.

Conclusion: Blood pressure is affected after five nights of CPAP interruption, along with a rapid return of sleep apneas, nocturnal hypoxic events, daytime sleepiness and increased hemoglobin levels, but arterial stiffness was not affected. Blood pressure was affected in women only, suggesting a sex-related CPAP effect on blood pressure.