Impact of hypertension on cerebral microvascular structure in CPAP-treated obstructive sleep apnoea patients: a diffusion magnetic resonance imaging study
Obstructive sleep apnoea (OSA) is a highly prevalent sleep-related breathing disorder associated with hypertension, impaired peripheral vascular function and an increased risk of stroke. Evidence suggests that abnormalities of the cerebral microcirculation, such as capillary rarefication, may be present in these patients. We evaluated whether the presence of hypertension may affect the cerebral capillary architecture and function assessed by Intravoxel Incoherent Motion (IVIM) magnetic resonance imaging (MRI) in patients with continuous positive airway pressure (CPAP)-treated OSA.
Forty-one patients (88% male, mean age 57 ± 10 years) with moderate-to-severe OSA were selected and divided into two groups (normotensive vs. hypertensive). All hypertensive OSA patients were adherent with their antihypertensive medication. Cerebral microvascular structure was assessed in grey (GM) and white matter (WM) using an echo-planar diffusion imaging sequence with 14 different b values. A step-wise IVIM analysis algorithm was applied to compute true diffusion (D), perfusion fraction (f) and pseudo-diffusion (D*) values. Group comparisons were performed with the Wilcoxon-Mann-Whitney-Test. Regression analysis was adjusted for age.
Diffusion- and perfusion-related indexes in middle-aged OSA normotensive patients were quantified in both tissue types (D [10−3 mm2/s]: GM = 0.83 ± 0.03; WM = 0.72 ± 0.03; f (%) GM = 0.09 ± 0.01; WM = 0.06 ± 0.01; D* [10−3 mm2/s]: GM = 7.72 ± 0.89; WM = 7.38 ± 0.98). In the examined tissue types, hypertension did not result in changes on the estimated MRI IVIM index values.
Based on IVIM analysis, cerebral microvascular structure and function showed no difference between hypertensive and normotensive patients with moderate-to-severe OSA treated with CPAP. Treatment adherence with antihypertensive drug regime and, in turn, controlled hypertension seems not to affect microvascular structure and perfusion of the brain.
ClinicalTrials.gov Identifier: NCT02493673
KeywordsObstructive sleep apnoea Cerebral microvascular structure Magnetic resonance imaging Hypertension
continuous positive airway pressure
Epworth Sleepiness Scale
oxygen desaturation index
obstructive sleep apnoea
Conception and design: MK, CR, AB. Funding: MK. Trial conduct: ST, FL. Analysis and interpretation of data: ST, FL, TG, CR, MK, AB, SW. Drafting the article: ST. Revising the article for important intellectual content and final approval: all authors.
This work received support from the Swiss National Science Foundation (Grant no. 32003B_143365/1), Lunge Zurich and the University of Zurich Clinical Research Priority Program Sleep and Health. This work was also supported by the Clinical Research Priority Program of the University of Zurich for the Hypertension Research Network (HYRENE).
Compliance with ethical standards
Conflict of interest
The authors declare the following conflicts of interest: ST, FL, CR, SW and AB have nothing to disclose. MK reports grants from University of Zurich and grants from Lunge Zurich during the conduct of the study. MK and TG report personal fees from Bayer AG, outside the submitted work.
All procedures performed in the studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.
Informed consent was obtained from all individual participants included in the study.
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