The brain has its own waste disposal system, and it works mostly while you sleep. A new study published in Neuroradiology suggests that when chronic insomnia disrupts this system, a key brain structure called the choroid plexus becomes enlarged, and the changes track with measurable cognitive decline.
The findings offer some of the clearest structural evidence yet that poor sleep may damage the brain’s ability to clean itself, and that this damage has real consequences for thinking and memory.
What They Found
Researchers at Guangdong Second Provincial General Hospital in Guangzhou, China, enrolled 107 patients with chronic insomnia and 68 healthy controls. All participants underwent brain MRI scans using a technique called diffusion tensor imaging, and completed two standard cognitive assessments: the Montreal Cognitive Assessment (MoCA) and the Digit Span Test (DST).
The study zeroed in on two things: the volume of the choroid plexus, a small but critical structure inside the brain’s fluid-filled cavities, and an MRI measure called the DTI-ALPS index. The ALPS index is an indirect window into the glymphatic system, the brain’s network of perivascular channels that flushes waste products out of neural tissue. When water moves freely along these channels, the index is higher, signaling healthy glymphatic function.
The results were striking. Chronic insomnia patients whose cognitive scores indicated decline had significantly larger choroid plexuses than both healthy controls and insomnia patients whose cognition remained normal. Among those with cognitive decline, choroid plexus volume correlated negatively with MoCA scores (r = -0.350, p = 0.009) and DST scores (r = -0.273, p = 0.044). In plain terms, the bigger the choroid plexus, the worse the cognitive performance.
At the same time, the DTI-ALPS index was lower in insomnia patients with cognitive decline, suggesting impaired glymphatic clearance. Choroid plexus volume was also negatively correlated with the ALPS index (r = -0.342, p = 0.011), meaning that enlarged choroid plexuses tracked with worse glymphatic function. And the ALPS index itself was positively correlated with both MoCA (r = 0.295, p = 0.029) and DST (r = 0.269, p = 0.047), further tying glymphatic health to cognitive performance.
The choroid plexus volume alone was not a strong standalone diagnostic marker for detecting cognitive decline in insomnia (AUC = 0.65), suggesting that the real value is in the combined picture across all three measures.
Why It Matters
To understand why this matters, a quick look at two players is helpful.
The glymphatic system is the brain’s janitorial service. Named as a play on the lymphatic system and the glial cells that drive it, this network of channels surrounds blood vessels and carries cerebrospinal fluid (CSF) through brain tissue, sweeping away metabolic waste including the amyloid and tau proteins linked to Alzheimer’s disease. Critically, the glymphatic system is most active during sleep. When sleep is fragmented or insufficient, as in chronic insomnia, this cleanup is thought to be compromised.
The choroid plexus is the factory where most of that CSF is produced. It is a frilled, highly vascularized structure located in the brain’s ventricles, and it does more than just make fluid. It also acts as a gatekeeper, regulating which substances enter the CSF and helping to maintain the brain’s chemical balance. Some researchers have proposed that the choroid plexus may be an entry point for the glymphatic system’s waste clearance pathway.
The study suggests that choroid plexus enlargement in chronic insomnia patients with cognitive decline may reflect a compensatory response to impaired CSF dynamics, or it could signal inflammation-driven hypertrophy that further disrupts clearance. Either way, the structural change appears to be a visible marker of a deeper functional problem.
This is the first study to link choroid plexus volume, glymphatic function measured by DTI-ALPS, and cognitive performance in a single cohort of chronic insomnia patients. The triplet of associations is coherent: insomnia disrupts sleep, disrupted sleep impairs glymphatic clearance, impaired clearance leads to waste accumulation and inflammation, and the choroid plexus responds by enlarging. Over time, the accumulating damage shows up as poorer scores on tests of memory and attention.
If confirmed, these imaging markers could help identify which insomnia patients are at highest risk for cognitive decline, potentially enabling earlier intervention.
Limits
The study has important limitations. Its cross-sectional design captures a single snapshot in time, so it cannot establish whether choroid plexus enlargement causes cognitive decline or follows it, or whether a third factor drives both. Longitudinal studies that follow patients over months or years are needed to tease apart cause and effect.
The DTI-ALPS index is an indirect measure of glymphatic function, not a direct visualization of CSF flow through perivascular spaces. While widely used in research, it remains a proxy. The cohort was also drawn from a single hospital in China, which limits generalizability. And the cognitive assessments used are screening tools rather than comprehensive neuropsychological batteries, so subtler deficits may have been missed.
Bottom Line
Chronic insomnia patients with cognitive decline show enlarged choroid plexuses and reduced DTI-ALPS indices, with significant correlations linking all three measures. The findings strengthen the case that glymphatic dysfunction is a key mechanism connecting chronic sleep disruption to cognitive impairment. While not yet ready for clinical use, choroid plexus volume and the DTI-ALPS index may eventually serve as complementary imaging biomarkers for identifying insomnia patients at risk of deteriorating cognition.
Source
Liu J, Lin Q, Li J, Xu G, Liu M, Zhang T, Ma X. “Enlarged choroid plexus in chronic insomnia patients and its association with DTI-ALPS index alterations and cognitive decline.” Neuroradiology. 2026 Jun 25. doi: 10.1007/s00234-026-04065-x. PMID: 42347984.