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Sympathetic Overactivity Due to Sleep Fragmentation Is Associated With Elevated Diurnal Systolic Blood Pressure in Healthy Elderly Subjects: The PROOF-SYNAPSE Study
Study Questions:
Does sleep fragmentation predispose an elderly population to elevated blood pressure (BP)?
Methods:
Volunteer subjects (n = 780) were free of known sleep-disordered breathing, coronary heart diseases, and neurological disorders. In addition, subjects were excluded for heart failure, insulin-dependent diabetes mellitus, atrial fibrillation, or antiarrhythmic treatment, and a severe disease-limiting life expectancy. All subjects underwent one night home portable polygraphy, 24-hour electrocardiogram (ECG) monitoring, and 24-hour ambulatory BP monitoring. Sleep fragmentation was defined by using an autonomic arousal index (AAI), based on a shorter pulse transit time, calculated from the time interval between the ECG R wave and the point of pulse waveform detected by a finger probe.
Results:
Roughly one-quarter of the study group (57.4% women, with a mean age of 68.7 years) was a current/past smoker or was treated with antihypertensive medications. Multivariate regressions showed that sleep fragmentation, expressed by AAI, was associated with elevated diurnal (p = 0.008) and 24-hour (p = 0.005) systolic BP and higher risk for 24-hour (odds ratio, 1.70; 95% confidence interval, 1.04-2.80; p = 0.036) systolic hypertension, independently of confounders such as sleep-disordered breathing, body mass index, sex, diabetes, hypercholesterolemia, and self-reported sleep duration and quality.
Conclusions:
The authors concluded that in healthy elderly subjects, repetitive arousals during sleep are associated with elevated systolic BP and higher risk of hypertension, after controlling for confounders.
Perspective:
Obstructive sleep apnea has been associated with increased sympathetic activity as well as higher risk for hypertension. Shorter sleep duration has been associated with hypertension in a middle-aged population, but not in an elderly population. These results indicate that BP regulation could be influenced by sleep fragmentation, independent of confounders. Of additional interest was the observation that the highest tertile of sleep fragmentation showed not only the highest BP, but also the most daytime sleepiness. What remains to understand is how sleep disruption induces a rise in BP during wakefulness, and whether an intervention can lead to improved BP.
Keywords: Body Mass Index, Sleep Deprivation, Middle Aged, Pulse Wave Analysis, Coronary Disease, Blood Pressure, Hypercholesterolemia, Hypertension, Sleep Apnea, Obstructive
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