Background: Mechanisms underlying blood pressure (BP) changes in obstructive sleep apnoea (OSA) are incompletely understood. We assessed the associations between BP and selected polysomnography (PSG) traits: sleep depth, airflow limitation measurements and OSA-specific hypoxic burden.
Methods: This cross-sectional analysis included 2055 participants from the Multi-Ethnic Study of Atherosclerosis who underwent PSG and BP measurements in 2010-2013. Sleep depth was assessed using the 'OR product', a continuous measure of arousability. Airflow limitation was assessed by duty cycle (Ti/Tt) and % of breaths with flow limitation, and hypoxia by 'hypoxic burden'. Primary outcomes were medication-adjusted systolic BP (SBP) and diastolic BP (DBP). We used generalised linear models adjusted for age, sex, race/ethnicity, smoking, education, body mass index, alcohol use, periodic limb movements and alternative physiological disturbances.
Results: The sample had a mean age of 68.4 years and apnoea-hypopnoea index of 14.8 events/hour. Sleep depth was not significantly associated with BP. Every 1 SD increment in log-transformed non-rapid eye movement duty cycle was associated with 0.9% decrease in SBP (95% CI: 0.1% to 1.6%), even after adjusting for sleep depth and hypoxic burden. Every 1 SD increment in log-transformed hypoxic burden was associated with a 1.1% increase in SBP (95% CI: 0.1% to 2.1%) and 1.9% increase in DBP (95% CI: 1.0% to 2.8%) among those not using hypertension medications.
Conclusions: Higher duty cycle was associated with lower SBP overall and hypoxic burden with higher SBP and DBP among non-BP medication users. These findings suggest changes in both respiratory effort and oxygenation during sleep influence BP.
Keywords: duty cycle; hypertension; hypoxia; inspiratory flow limitation; sleep apnoea.
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Conflict of interest statement
Competing interests: AA has received personal fees from Somnifx and Apnimed. MY has received personal fees from Cerebra Health. MY has patent for method and software to determine quality of sleep and wakefulness. MY has patent for method and apparatus for arousal intensity scoring. SSR has received grants and personal fees from Jazz Pharma. SSR has received personal fees from Respircardia.
A Systematic Assessment of the Association of Polysomnographic Indices With Blood Pressure: The Multi-Ethnic Study of Atherosclerosis (MESA)DA Dean et al. Sleep 38 (4), 587-96. PMID 25348124.Our results support the use of a currently recommended apnea-hypopnea index definition as a marker of blood pressure risk and indicate that measurement of limb movements …
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Continuous Positive Airways Pressure for Obstructive Sleep Apnoea in AdultsTL Giles et al. Cochrane Database Syst Rev (1), CD001106. PMID 16437429. - ReviewCPAP is effective in reducing symptoms of sleepiness and improving quality of life measures in people with moderate and severe obstructive sleep apnoea (OSA). It is more …