Cortical arousal, a component of sleep apnea, is associated with lower grey matter volume in the left frontal pole, a new study in the Sleep journal shows. This area of the brain is associated with cognitive processes. Relatedly, apnea was associated with lower cognitive flexibility and lower selective attention.
The researchers for a study for Sleep Research Society analyzed polysomnographic (PSG) recordings with a principal component analysis. Rather than look at breathing-related disturbances or slow wave sleep, the researchers studied specific sleep characteristics.
The researchers included PSG during the first follow-up examination of the BiDirect Study, a study out of Munster, Germany, that included three cohorts of individuals between the ages of 35 and 65. A 3T scanner captured 3D head images, including 160 sagittal slices (2 mm thickness, reconstructed to 1 mm): TR = 7.26 ms, TE = 3.56 ms, 9° flip angle, matrix dimension 256 × 256, FOV = 256 mm x 256 mm.
Recordings took place between 10 pm and 6 am. Measurements included electroencephalogram (F4-M1, C4-M1, C3-M2, O4-M1), electrooculogram (2 electrodes), electrocardiogram (2 electrodes), surface electromyogram (electrodes on the chin and both anterior tibialis muscles), pulse oximetry, nasal pressure, respiratory inductive plethysmography, tracheal microphone, and body position sensors. Bipolar surface electrodes from the electromyogram, attached along the anterior tibialis muscle, captured limb movements.
Brain analysis showed a significant association between the first PSG analysis component and lower gray matter volume in the left frontal pole (Brodmann Area 10; Peak MNI coordinates: X = -22.5, Y = 64.5, Z = -4.5, cluster size = 168 voxel). The apnea-related PSG-component 1 (β = 0.05; P = .008; model P < .001; model R2 = 0.11) was associated with lower performance (ie, more time needed) on the Trail-Making Test difference score, after controlling for age, sex, and body mass index.
That the PSG was located in a hospital counted for one limitation: a study in the patients’ home bedrooms would have been preferable. Also, the American Academy of Sleep Medicine scoring guidelines changed over time.
Although the study was only one night, the results “advance our understanding of disrupted sleep, particularly with regard to breathing disturbances, cortical arousal, and its associations with lower gray matter volume,” the researchers said.
Hermesdorf M, Szentkirályi A, Teismann H, Teismann I, Young P, Berger K. Sleep characteristics, cognitive performance and gray matter volume: findings from the BiDirect study. Sleep. 2020 Oct 8:zsaa209. doi: 10.1093/sleep/zsaa209