Reduced brain gray matter concentration in patients with obstructive sleep apnea syndrome

Abstract

Study objectives: To investigate differences in brain gray matter concentrations or volumes in patients with obstructive sleep apnea syndrome (OSA) and healthy volunteers.

Designs: Optimized voxel-based morphometry, an automated processing technique for MRI, was used to characterize structural differences in gray matter in newly diagnosed male patients.

Setting: University hospital.

Patients and participants: The study consisted of 36 male OSA and 31 non-apneic male healthy volunteers matched for age (mean age, 44.8 years).

Interventions: Using the t-test, gray matter differences were identified. The statistical significance level was set to a false discovery rate P < 0.05 with an extent threshold of k(E) > 200 voxels.

Measurements and results: The mean apnea-hypopnea index (AHI) of patients was 52.5/h. On visual inspection of MRI, no structural abnormalities were observed. Compared to healthy volunteers, the gray matter concentrations of OSA patients were significantly decreased in the left gyrus rectus, bilateral superior frontal gyri, left precentral gyrus, bilateral frontomarginal gyri, bilateral anterior cingulate gyri, right insular gyrus, bilateral caudate nuclei, bilateral thalami, bilateral amygdalo-hippocampi, bilateral inferior temporal gyri, and bilateral quadrangular and biventer lobules in the cerebellum (false discovery rate P < 0.05). Gray matter volume was not different between OSA patients and healthy volunteers.

Conclusions: The brain gray matter deficits may suggest that memory impairment, affective and cardiovascular disturbances, executive dysfunctions, and dysregulation of autonomic and respiratory control frequently found in OSA patients might be related to morphological differences in the brain gray matter areas.

Figure 1

The prior images of brain tissue partitions and averaged T1 template in voxel-based morphometry (A) Gray matter, (B) white matter, and (C) CSF prior maps. Averaged T1 template was created from all OSA patients and healthy volunteers

Figure 2

A statistical brain map showing a decrease in gray matter concentration (GMC) in patients with severe obstructive sleep apnea syndrome (OSA). (A) Gray matter concentrations were reduced in patients with OSA compared with healthy volunteers (at the false discovery rate corrected P < 0.05, independent t test) in the following brain structures: bilateral superior frontal gyri, left gyrus rectus, and bilateral frontomarginal gyri, bilateral anterior cingulate gyri, right anterior insular gyrus, bilateral caudate nuclei, bilateral thalami, bilateral amygdala and hippocampi, bilateral inferior temporal gyri, and bilateral cerebellar cortices. The results were superimposed on the 2-dimensional planes of averaged T1 template of all subjects. Scales in color bar are t scores. Left-hand sides of images represent the left hemisphere of the brain. (B) The overall areas with reduced gray matter concentrations are shown in a three-dimensional brain rendering view.