Lead. Every night we sleep, our brains perform a deep clean. Cerebrospinal fluid washes through neural tissue, flushing out metabolic waste products that accumulate during waking hours, including the proteins amyloid-beta and tau that are hallmarks of Alzheimer’s disease. This waste removal system, known as the glymphatic system, has emerged as one of the most important discoveries in sleep neuroscience over the past decade. What happens to it when someone cannot sleep? A study published July 20 in the Journal of Magnetic Resonance Imaging offers the first multiparametric MRI evidence that insomnia in middle-aged and older women is linked to measurable disruptions in the brain’s fluid clearance machinery, along with structural changes in the brain regions that produce and regulate this cleaning fluid.
What they found. The study, led by Rui Wang and colleagues from the University of Macau, Guangzhou University of Chinese Medicine, the University of Maryland School of Medicine, and Harvard Medical School, enrolled 28 women with insomnia disorder (average age 58.2) and 46 healthy women without sleep complaints (average age 56.3). All participants underwent 3T MRI scans using a multiparametric protocol designed to probe different aspects of the brain’s neurofluid system.
The results revealed three significant differences in the insomnia group. First, there was reduced BOLD-CSF coupling, a measure of how well brain activity and cerebrospinal fluid flow coordinate with each other. In healthy brains, waves of CSF flow are tightly synchronized with slow oscillations in neural activity, a relationship that drives glymphatic clearance during sleep. In the women with insomnia, this coordination was significantly weaker. The coupling was particularly disrupted in the right posterior medial cortex, a region involved in the default mode network, which is known to be vulnerable to sleep disruption.
Second, the choroid plexus, the tissue inside the brain’s ventricles that produces most of the cerebrospinal fluid, was enlarged in the insomnia group. It occupied 1.72 percent of total intracranial volume, compared to 1.55 percent in healthy controls. The choroid plexus is also a key interface between the brain and the immune system, and its enlargement may signal chronic inflammation, a known consequence of prolonged sleep disturbance.
Third, the nucleus basalis of Meynert, a small but critical cluster of neurons in the basal forebrain that controls sleep-wake transitions and attention, was smaller in the insomnia group: 201.75 cubic millimeters versus 217.47 cubic millimeters in controls. This cholinergic nucleus is one of the first brain regions to degenerate in Alzheimer’s disease, and its reduced volume in chronic insomnia raises questions about long-term neurodegenerative risk.
One marker did not differ between the groups. The DTI-ALPS index, which measures water diffusion along perivascular spaces as a proxy for glymphatic function, was essentially identical in the two groups (p=0.85). This negative finding is important because it suggests that while insomnia affects multiple components of the neurofluid system, it does not uniformly disrupt all aspects of perivascular clearance, at least as measured by current MRI techniques.
The researchers built a four-marker statistical model combining BOLD-CSF coupling, choroid plexus volume, nucleus basalis volume, and a measure of CSF tracer dynamics. This model classified women with insomnia versus healthy controls with an area under the curve (AUC) of 0.785 and an overall accuracy of 71.9 percent. While not yet a diagnostic tool, the model demonstrates that these imaging markers carry meaningful information about the brain state associated with chronic insomnia.
Why it matters. Insomnia is the most common sleep disorder worldwide, and its prevalence increases with age, particularly in women. Yet the biological mechanisms that link poor sleep to long-term health outcomes remain incompletely understood. This study provides a window into those mechanisms by showing that insomnia is associated not just with subjective sleep complaints but with objective, measurable alterations in the brain’s fluid management infrastructure.
The findings are especially relevant to the connection between sleep disruption and neurodegenerative disease. Both the glymphatic system and the nucleus basalis of Meynert have been independently implicated in Alzheimer’s pathology. The choroid plexus volume changes may reflect an inflammatory component of chronic insomnia. Together, these markers suggest that insomnia in middle-aged and older women may accelerate or parallel some of the same brain changes seen in early neurodegeneration.
The correlation between the MRI markers and clinical scores strengthened this interpretation. Women with worse scores on the Pittsburgh Sleep Quality Index and the Insomnia Severity Index showed more pronounced alterations in BOLD-CSF coupling and choroid plexus volume. Similarly, higher scores on the Fatigue Severity Scale were linked to greater neurofluid disruption. These associations link the MRI findings to real-world symptoms that patients actually experience.
Limits. The study is cross-sectional, meaning it captures a snapshot in time. It cannot determine whether the observed brain changes cause insomnia, result from years of poor sleep, or reflect a shared underlying vulnerability. Longitudinal studies that follow women over time are needed to establish directionality. The sample size is modest (74 women total), and the study included only women, so the findings cannot yet be generalized to men or to younger populations. The four-marker model, while promising, has not been validated in an independent cohort and should be interpreted cautiously. Finally, DTI-ALPS is an indirect measure of glymphatic function, and its lack of group difference may reflect limitations of the technique rather than the absence of a biological difference.
Bottom line. Chronic insomnia in middle-aged and older women is associated with reduced coordination between brain activity and cerebrospinal fluid flow, enlargement of the brain’s fluid-producing choroid plexus, and shrinkage of a key sleep-wake control nucleus. These findings suggest that insomnia involves measurable disruptions in the brain’s waste clearance and fluid regulation systems, mechanisms that may help explain the well-documented link between chronic sleep problems and long-term brain health declines.
Source. Wang R, Wang K, Guo Q, et al. “Altered neurofluid dynamics in middle-aged and older women with insomnia disorder: A multiparametric MRI study.” Journal of Magnetic Resonance Imaging, July 20, 2026. DOI: 10.1002/jmri.70417. Multi-institutional: University of Macau, Guangzhou University of Chinese Medicine, University of Maryland School of Medicine, Harvard Medical School, and others. Funding: National Natural Science Foundation of China (82330058, T2341014). PMID: 42476764.