Regional Cerebral Blood Flow during Wakeful Rest in Older Subjects with Mild to Severe Obstructive Sleep Apnea

Abstract

Objectives: To evaluate changes in regional cerebral blood flow (rCBF) during wakeful rest in older subjects with mild to severe obstructive sleep apnea (OSA) and healthy controls, and to identify markers of OSA severity that predict altered rCBF.

Design: High-resolution (99m)Tc-HMPAO SPECT imaging during wakeful rest.

Setting: Research sleep laboratory affiliated with a University hospital.

Participants: Fifty untreated OSA patients aged between 55 and 85 years, divided into mild, moderate, and severe OSA, and 20 age-matched healthy controls.

Interventions: N/A.

Measurements: Using statistical parametric mapping, rCBF was compared between groups and correlated with clinical, respiratory, and sleep variables.

Results: Whereas no rCBF change was observed in mild and moderate groups, participants with severe OSA had reduced rCBF compared to controls in the left parietal lobules, left precentral gyrus, bilateral postcentral gyri, and right precuneus. Reduced rCBF in these regions and in areas of the bilateral frontal and left temporal cortex was associated with more hypopneas, snoring, hypoxemia, and sleepiness. Higher apnea, microarousal, and body mass indexes were correlated to increased rCBF in the basal ganglia, insula, and limbic system.

Conclusions: While older individuals with severe obstructive sleep apnea (OSA) had hypoperfusion in the sensorimotor and parietal areas, respiratory variables and subjective sleepiness were correlated with extended regions of hypoperfusion in the lateral cortex. Interestingly, OSA severity, sleep fragmentation, and obesity correlated with increased perfusion in subcortical and medial cortical regions. Anomalies with such a distribution could result in cognitive deficits and reflect impaired vascular regulation, altered neuronal integrity, and/or undergoing neurodegenerative processes.

Keywords: SPECT; aging; cerebral perfusion; neuroimaging; obstructive sleep apnea; regional cerebral blood flow; snoring.

Figure 1

Location of the significant reductions in regional cerebral blood flow (rCBF) in severe obstructive sleep apnea (OSA) subjects compared with controls. (A) Glass view of the significant clusters and (B) overlays of significant regions on the SPECT template. Hypoperfusions were found in the left superior and inferior parietal lobules, the left precentral gyrus, bilateral postcentral gyri, and right precuneus gyrus. Left side of images represents the left hemisphere of the brain.

Figure 2

Hypoperfused regions associated with OSA severity. Location of hypoperfusions that correlated with variables representing more severe obstructive sleep apnea (OSA). Regions showing hypoperfusions were as follow: (A) and (B) left inferior and middle frontal, precentral, postcentral, and middle temporal gyri, inferior parietal lobule, and right precuneus; (C) left parahippocampal, anterior temporal pole, and inferior frontal gyri; (D) left dorsolateral prefrontal cortex; (E) bilateral dorsomedial prefrontal cortex; (F) right postcentral gyrus. Results are overlays on the SPECT template and left side of images represent the left hemisphere of the brain.

Figure 3

Hyperperfused regions associated with OSA severity. Locations of hyperperfusion that correlated with variables representing more severe obstructive sleep apnea (OSA). Regions showing hyperperfusion were as follow: (A) right basal ganglia, amygdala, and hippocampus; (B) right parahippocampal gyrus, insular cortex, and left putamen; (C) bilateral hippocampi, left parahippocampal gyrus, and globus pallidus. Results are overlays on the SPECT template and left side of images represent the left hemisphere of the brain.