Polysomnography-derived sleep parameters as a determinant of nocturnal blood pressure profile in patients with...

Obstructive sleep apnea causes blood pressure (BP) surges during sleep, which may lead to increased sleep-onset cardiovascular events. The authors recently developed an oxygen-triggered nocturnal BP monitoring system that initiates BP measurements when oxygen desaturation (SpO₂ ) falls below a variable threshold. The association between nocturnal BP parameters obtained by nocturnal BP monitoring and simultaneously examined polysomnography-derived sleep parameters in 116 patients with obstructive sleep apnea (mean age 57.9 years, 85.3% men) was studied. In multivariable analysis with independent factors of age, body mass index, sex, and polysomnography-derived measures (apnea-hypopnea index, apnea index, arousal index, lowest SpO₂ , and SpO₂  < 90%), apnea-hypopnea index (β = .26, P = .02) and lowest SpO₂ (β = -.34, P < .001) were independent determinants of hypoxia-peak systolic BP (SBP), defined as the maximum SBP value measured by nocturnal BP monitoring. Similarly, apnea-hypopnea index (β = .21, P = .04) and lowest SpO₂ (β = -.49, P < .001) were independent determinants of nocturnal SBP surge, defined as the difference between the hypoxia-peak SBP and the average of the SBP values within 30 minutes before and after the hypoxia-peak SBP, measured by the fixed-interval function in the manner of conventional ambulatory BP monitoring. In conclusion, in polysomnography-derived parameters, lowest SpO₂ , defined as the minimum SpO₂ value during sleep, is the strongest independent determinant of hypoxia-peak SBP and nocturnal SBP surge measured by nocturnal BP monitoring. Our findings suggest that the severity of the decrease in SpO₂ and the frequency of such decreases would be important indicators to identify high-risk patients who are likely to develop cardiovascular events specifically during sleep.