Obstructive sleep apnea and white matter hyperintensities: correlation or causation?

Alteration of multilayer network perspective on gray and white matter connectivity in obstructive sleep apnea

PURPOSE

The objective of this research was to examine changes in the neural networks of both gray and white matter in individuals with obstructive sleep apnea (OSA) in comparison to those without the condition, employing a comprehensive multilayer network analysis.

METHODS

Patients meeting the criteria for OSA were recruited through polysomnography, while a control group of healthy individuals matched for age and sex was also assembled. Utilizing T1-weighted imaging, a morphometric similarity network was crafted to represent gray matter, while diffusion tensor imaging provided structural connectivity for constructing a white matter network. A multilayer network analysis was then performed, employing graph theory methodologies.

RESULTS

We included 40 individuals diagnosed with OSA and 40 healthy participants in our study. Analysis revealed significant differences in various global network metrics between the two groups. Specifically, patients with OSA exhibited higher average degree overlap and average multilayer clustering coefficient (28.081 vs. 23.407, p < 0.001; 0.459 vs. 0.412, p = 0.004), but lower multilayer modularity (0.150 vs. 0.175, p = 0.001) compared to healthy controls. However, no significant differences were observed in average multiplex participation, average overlapping strength, or average weighted multiplex participation between the patients with OSA and healthy controls. Moreover, several brain regions displayed notable differences in degree overlap at the nodal level between patients with OSA and healthy controls.

CONCLUSION

Remarkable alterations in the multilayer network, indicating shifts in both gray and white matter, were detected in patients with OSA in contrast to their healthy counterparts. Further examination at the nodal level unveiled notable changes in regions associated with cognition, underscoring the effectiveness of multilayer network analysis in exploring interactions across brain layers.

Aneurysmal subarachnoid hemorrhage occurring during sleep: Clinical characteristics and risk factors

BACKGROUND

Aneurysmal subarachnoid hemorrhage (aSAH) is known to be triggered by several specific human activities. Sleep, by contrast, has not been considered a triggering activity for aSAH, and clinical characteristics of patients who sustain aSAH during sleep have rarely been reported in the literature.

METHODS

This is a retrospective analysis on the data acquired through a multicenter aSAH registry. Between January 2019 and December 2021, a total of 732 aSAH patients had been registered into our database. After excluding 109 patients whose activities at aSAH onset had been unidentifiable, the remaining 623 aSAH patients were dichotomized to 59 patients who sustained aSAH during sleep (Sleep group) and 564 patients who sustained aSAH during daytime activities (Awake group). Two-group comparison of demographic variables and multivariate logistic regression analysis were performed to clarify their clinical characteristics and identify potential risk factors.

RESULTS

The Sleep group exhibited significantly higher frequencies of diabetes (15.5 % vs. 6.4 %, p = 0.01) and antiplatelet use (13.8 % vs. 4.6 %, p=0.004) than the Awake group. Furthermore, multivariate logistic regression analysis showed that diabetes (OR, 3.051; 95 % CI, 1.281-7.268; p = 0.012) and antiplatelet use (OR, 3.640; 95 % CI, 1.422-9.316; p = 0.007) were correlated with aSAH occurring during sleep. There were no significant inter-group differences in the patient outcomes evaluated at discharge.

CONCLUSION

The current results indicate that risk factors may exist for aSAH occurring during sleep. Further investigations on how comorbidities such as diabetes, antiplatelet use and sleep apnea affect human hemodynamic and hemostatic parameters during sleep is warranted to better understand those relationships.

Correlation between obstructive sleep apnea and cerebral small vessel disease: a mendelian randomization study

BACKGROUND

Whether obstructive sleep apnea (OSA) is causally associated with an increased risk of cerebral small vessel disease (CSVD) remains controversial. We conducted a two-sample Mendelian randomization (MR) study to clarify the causal relationship between OSA and CSVD risk.

METHODS

Single-nucleotide polymorphisms associated with OSA at the genome-wide significance level (P < 5 × 10- 8) in the FinnGen consortium were selected as instrumental variables. Summary-level data for white matter hyperintensities (WMHs), lacunar infarctions (LIs), cerebral microbleeds (CMBs), fractional anisotropy (FA), and mean diffusivity (MD) were obtained from three meta-analyses of genome-wide association studies (GWASs). The random-effects inverse-variance weighted (IVW) method was selected for the major analysis. Weighted-median, MR-Egger, MR pleiotropy residual sum and outlier (MR-PRESSO), and leave-one-out analysis methods were implemented for the sensitivity analyses.

RESULTS

Genetically predicted OSA was not associated with LIs (odds ratio [OR] = 1.10, 95% confidence interval [CI] = 0.86-1.40), WMHs (OR = 0.94, 95% CI = 0.83-1.07), FA (OR = 1.33, 95% CI = 0.75-2.33), MD (OR = 0.93, 95% CI = 0.58-1.47), CMBs (OR = 1.29, 95% CI = 0.86-1.94), mixed CMBs (OR = 1.17, 95% CI = 0.63-2.17), and lobar CMBs (OR = 1.15, 95% CI = 0.75-1.76) in IVW method. The results of the sensitivity analyses were generally consistent with the major analyses.

CONCLUSIONS

This MR study does not support causal associations between OSA and the risk of CSVD in individuals of European ancestry. These findings need to be further validated in randomized controlled trials, larger cohort studies, and MR studies based on larger GWASs.

[Obstructive sleep apnea - underestimated cognitive impairments risk factor]

About 40% of cases of cognitive impairment (CI) are associated with modifiable risk factors, such as inactivity, hypertension, diabetes and obesity. Recently, sleep disorders, including obstructive sleep apnea syndrome (OSA), have been considered among these factors. OSA is one of the most widespread conditions among patients with CI. The pathogenesis of cerebral lesions in OSA is complex. Timely diagnosis and complex therapy of patients with OSA can reduce the risk, reduce the severity of CI and slow their progression. Along with non-drug methods of treatment, the use of the drug Cortexin with a multimodal mechanism of action can minimize the negative impact of OSA on the cognitive health of patients. Early detection and treatment of OSA can reduce the severity of CI and slow their progression.