Obstructive Sleep Apnea Status Affects Glymphatic System Function and Cognitive Function

An analysis using data from a community-based prospective cohort of patients with obstructive sleep apnea (OSA) showed that OSA severity inversely correlated with the glymphatic system function and changes in OSA status over time were associated with cognitive performance changes. These findings suggest that this effect might be reversible and thus, sustained proper management of OSA should potentially be considered for effective prevention as well as management of cognitive decline.¹

At baseline, among 1110 participants (mean age, 58.0 [SD, 6.0] years; 517 [SD, 46.6%] men), 621 were categorized as non-OSA, 338 had mild OSA, and the remaining 151 had moderate-to-severe OSA. At a 4-year follow-up, 458 patients were categorized as OSA-free, 114 patients had improved OSA, 303 participants had stationary OSA, and 235 participants had progressed OSA.

Led by senior author Chang-Ho Yun, MD, PhD, professor of neurology at Seoul National University Bundang Hospital, and colleagues, the study included patients who had both baseline and 4-year follow-up polysomnography, brain MRI with diffusion tensor imaging (DTI), and comprehensive cognitive assessment data. At both baseline and follow-up, researchers categorized patients as non-OSA (AHI less than 5), mild OSA (at least a 5 AHI score but lower than 15), and moderate-to-severe OSA (AHI at least 15) groups.

Presented at the 2024 SLEEP Annual Meeting, held June 1 to 5, in Houston, Texas, patients were then categorized as OSA-free (non-OSA at both baseline and follow-up), improved OSA, stationary OSA, and progressed to OSA according to the longitudinal change in OSA severity at 4-year follow-up. Authors then measured the glymphatic system function among the participants using DTI along the perivascular space (DTI-ALPS) index.

Top Clinical Takeaways

OSA severity inversely correlated with the glymphatic system function, as shown by the DTI-ALPS index.
Changes in OSA status over time were associated with changes in cognitive performance, indicating potential reversibility of cognitive decline with effective OSA management.
Improved OSA status over 4 years corresponded with the highest increase in DTI-ALPS index, followed by OSA-free, stationary OSA, and progressed OSA groups.

At baseline, the non-OSA group of patients showed a higher DTI-ALPS index compared with the remaining groups (both, P <.001) and revealed that the apnea-hypopnea index (AHI) was inversely correlated with DTI-ALPS index (R = -.169; P <.001). At follow-up of 4 years, the change in the DTI-ALPS index (ΔDTI-ALPS) was reported the highest in the improved OSA group, followed by the OSA free, stationary OSA, and progressed OSA groups. Notably, the ΔDTI-ALPS over 4-years inversely correlated with ΔAHI (R = -.171; P <.001 for the entire study population and R = -.218; P <.001 for the population which excluded the OSA-free subgroup). Additional findings showed that ΔDTI-ALPS over 4-years correlated with the changes in the visual reproduction–immediate recall (R = .233), delayed recall (R = .178), and recognition (R = .188) scores (all, P <.001).

According to a similar study published in Sleep Medicine, findings showed that glymphatic system dysfunction among patients with OSA correlated with OSA severity.² These results support the new study presented at SLEEP 2024 and provided further evidence on the effects of OSA on increased risk of developing dementia, highlighting the importance of OSA treatment.

In the prior study, investigators enrolled 24 patients with OSA and 24 healthy controls. All of the participants underwent DTI MRI using the same 3T MRI scanner, and from there, the researchers calculated the DTI-ALPS index from the DTI. The authors assessed the differences in the DTI-ALPS index between patients with OSA and healthy controls. Additionally, they performed a correlation analysis between the DTI-ALPS index and clinical characteristics.

Findings showed that the DTI-ALPS index significantly differed between the groups. Authors reported that the DTI-ALPS in patients with OSA was significantly lower compared with the healthy controls (1.30450 vs. 1.61600; P = .00006, respectively). Moreover, investigators observed that the DTI-ALPS index was significantly negatively correlated with the AHI in sleep stage N (r = -.427; P = .042) and oxygen desaturation index during sleep N (r = -.497; P = .036).