A large-scale study has revealed how problems with the brain’s waste removal system may lead to vascular dementia, the second most common form of dementia after Alzheimer’s disease. The research, involving brain scans from 3,750 people across four different groups, provides new insights into how cognitive decline develops and suggests potential pathways for treatment.
Researchers at USC’s Keck School of Medicine found that poor functioning of the brain’s waste clearance system, known as the glymphatic system, correlates strongly with decreased cognitive performance. The study appears in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.
“The most significant finding is that we found a clear link between DTI-ALPS and cognitive function in all four cohorts, with ages ranging from middle-age through older adulthood,” says Danny J. J. Wang, professor of neurology and radiology at USC’s Stevens Neuroimaging and Informatics Institute and the study’s senior author.
The research team used a specialized brain imaging technique called DTI-ALPS to measure how well the brain’s waste removal system was functioning. They found that people with lower scores on this measure also performed worse on tests of executive function, which includes abilities like memory, attention, and planning.
This link was consistently found across four different study groups, representing a diverse range of participants averaging between 56 and 76 years of age. The consistency of results across such varied populations strengthens confidence in the findings.
The researchers also discovered a possible explanation for how this process leads to cognitive decline. They found that problems with waste clearance appear to cause an accumulation of excess water in the brain’s white matter, which then leads to tissue damage and cognitive impairment.
“First waste clearance is impaired, which causes accumulation of free water in the brain’s white matter. That leads to tissue damage and eventually to cognitive impairment,” explains Xiaodan Liu, the study’s first author and assistant researcher at the University of California, San Francisco.
The findings could have significant implications for treating both vascular dementia and potentially Alzheimer’s disease. Wang suggests that enhancing glymphatic function through lifestyle changes such as exercise and improved sleep quality might help prevent or slow cognitive decline.
Vascular dementia shares many symptoms with Alzheimer’s disease, including problems with memory, decision-making, and language. It typically develops due to damage to small blood vessels in the brain, a condition known as cerebral small vessel disease. As the global population ages, understanding and treating these conditions becomes increasingly crucial for public health.
The research was supported by the National Institute of Neurological Disorders and Stroke and the National Institute on Aging, part of the National Institutes of Health.