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Study Uncovers Association Between Sleep Apnea and Lower Brain Volume
The medial temporal lobe (MTL) region of the brain may be especially vulnerable to reduced volume and other effects of sleep-disordered breathing (SDB), particularly in individuals with amyloid plaques. Results from the randomized study were published in an open access format online in the journal Neurology.
“We found that people with amyloid plaques who had more severe sleep apneas also were more likely to have lower volumes in the medial temporal lobe area of the brain, including the hippocampus, which plays a role in memory and Alzheimer’s disease,” said study author Geraldine Rauchs, PhD, of Inserm in Caen, France. “The people who did not have amyloid plaques did not have this lower brain volume, even if they had severe sleep apneas.”
The study included 122 patients with data from the Age-Well randomized controlled trial of the Medit-Ageing European project collected between 2016 and 2020. The patients were over 65 years old, and free of neurological, psychiatric, and/or chronic medical diseases at baseline. The authors examined the cohort as a whole and in subgroups organized according to amyloid status.
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Study measures at baseline included a neuropsychological evaluation, in-home polysomnography, a Florbetapir positron emission tomography, and magnetic resonance imaging (MRI) with high-resolution assessment of the medial temporal lobe and hippocampal subfields. Researchers conducted multiple linear regressions to evaluate interactions between amyloid status and SDB severity on brain volume in the MTL subregions, controlling for age, sex, education, and APOE4 status. Secondary analyses examined links between SDB, MTL atrophy, and episode memory performance at baseline and at follow-up (mean=20.66 months).
The apnea-hypopnea index interacted with entorhinal (β=-0.81, p<0.001, pη2=0.19), whole hippocampal (β=-0.61, p<0.001, pη2=0.10), subiculum (β=-0.56, p=0.002, pη2=0.08), CA1 (β=-0.55, p=0.002, pη2=0.08), and DG (β=-0.53, p=0.003, pη2=0.08) volumes, such that higher sleep apnea severity was related to lower MTL subregions volumes in amyloid-positive individuals but not those who were amyloid-negative. In the whole cohort, lower whole hippocampal (r=0.27, p=0.005) and CA1 (r=0.28, p=0.003) volumes at baseline were associated with worse episodic memory performance at follow-up.
“Our results suggest that some people may be more vulnerable to the adverse effects of sleep apnea,” Rauchs said. “People who are in the very early stages of the Alzheimer’s continuum showed a specific vulnerability to sleep apneas. Further studies should look at whether treating sleep-disordered breathing could potentially improve cognition and prevent or delay neurodegeneration.”
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