# The Prevalence of Sleep Disorders in Populations with Glymphatic Dysfunction: A Systematic Review and Meta-Analysis

## TL;DR

This study finds that sleep disorders are common in people with impaired brain waste clearance, suggesting a link that could impact brain health and aging.

## Contribution

The study provides the first meta-analysis quantifying the prevalence of sleep disorders in populations with glymphatic dysfunction.

## Key findings

- Sleep disorders affect 44.9% of individuals with impaired glymphatic-related function.
- Older age and case–control study design are significant contributors to heterogeneity in results.
- The co-occurrence of sleep disorders and glymphatic dysfunction suggests a potential bidirectional relationship.

## Abstract

Good sleep is essential for keeping the brain healthy. During sleep, the brain uses a natural cleaning system to remove waste products that can damage brain cells if they build up over time. Problems with this cleaning process have been linked to brain diseases, but it is still unclear how common sleep disorders are in people who show signs of poor brain waste clearance. In this study, we reviewed and combined results from many previous human studies to answer this question. We found that sleep disorders are very common in people with signs of impaired brain waste removal, affecting almost one in two individuals. This rate is much higher than is usually seen in the general population. Our findings suggest that sleep problems and poor brain cleaning often occur together and may worsen each other. Understanding this link is important because improving sleep could help protect brain health, reduce the risk of memory problems, and support healthy ageing. These results highlight the value of early sleep screening and sleep care as part of strategies to prevent brain diseases.

The glymphatic system supports metabolic waste clearance during sleep and is essential for brain homeostasis. Disruption of this system has been linked to sleep disorders, yet the overall prevalence of sleep disorders in populations showing impaired glymphatic-related function remains unclear. This systematic review and meta-analysis evaluated the prevalence of sleep disorders in human cohorts with structural, functional, or biochemical imaging markers of impaired glymphatic activity. Following PRISMA guidelines, major databases were searched up to August 2025. Eligible observational studies reported sleep disorder prevalence in populations characterized by enlarged perivascular spaces, white matter hyperintensities, DTI-ALPS (DTI-ALPS: Diffusion tensor image analysis along perivascular space) alterations, ultrafast fMRI (fMRI: functional magnetic resonance) indices, or CSF/PET (CSF: cerebrospinal fluid; PET: positron emission tomography) clearance deficits. Random-effects models generated pooled estimates, and heterogeneity, publication bias, and moderators were examined using I2 statistics, Egger’s test, trim-and-fill, and meta-regression. Nineteen studies (≈4500 participants) met the inclusion criteria. The pooled prevalence of sleep disorders in populations with impaired glymphatic-related function was 44.9% (95% CI: 34.9–55.3%), with substantial heterogeneity (I2 ≈ 95%). Meta-regression identified older age and case–control design as significant contributors, while imaging modality, sex distribution, and sample size were not. Publication bias was minimal. Sleep disorders are common among individuals with impaired glymphatic-related markers, reflecting co-occurrence rather than causality. Standardized longitudinal studies are needed to clarify mechanisms and clinical relevance.