Alterations of neurofluid transport in patients with obstructive sleep apnea and insomnia disorder

Sleep appears to modulate brain-wide neurofluid transport, encompassing the movement and exchange of cerebrospinal and interstitial fluids via perivascular pathways. However, neurofluid transport in common sleep disorders, such as insomnia disorder and obstructive sleep apnea, requires further assessment. In this study, we recruited 159 participants: patients with moderate to severe obstructive sleep apnea (n = 36) or chronic insomnia disorder (n = 62), and healthy controls (n = 61). Participants underwent structural magnetic resonance imaging, polysomnography, the Pittsburgh Sleep Quality Index, and the STOP-Bang questionnaires. Here, neurofluid transport is indirectly assessed using two noninvasive MRI indices (i.e., the perivascular space volume fraction and diffusion tensor imaging along perivascular spaces). Patients with obstructive sleep apnea exhibited a significantly larger perivascular space volume fraction compared with patients with insomnia disorder (p = 0.042) and healthy controls (p = 0.032), whereas no group differences were observed for the diffusion-based index. Partial correlation analyses, adjusted for age, sex, and body mass index, revealed that in obstructive sleep apnea, a larger perivascular space volume fraction was associated with less sleep disturbance (r = -0.35, p = 0.04), and diffusion measures increased with snoring severity (r = 0.38, p = 0.03). In insomnia disorder, a larger perivascular space volume fraction was associated with a higher nocturnal wake index (r = 0.38, p = 0.006) and an elevated risk of blood pressure (r = 0.50, p < 0.001), while inversely relating to subjective sleep quality (r = -0.35, p = 0.01). Our results highlight different patterns of neurofluid transport alterations across obstructive sleep apnea and insomnia disorder.