Scientists from Nanyang Technological University, Singapore (NTU Singapore) have found that the brain's waste removal system often becomes blocked in people who show early signs of Alzheimer's disease. These blockages interfere with the brain's ability to clear harmful substances and may appear well before clear dementia symptoms develop.

The clogged pathways are known as "enlarged perivascular spaces," and the findings suggest they could serve as an early warning signal for Alzheimer's, the most common form of dementia.

"Since these brain anomalies can be visually identified on routine magnetic resonance imaging (MRI) scans performed to evaluate cognitive decline, identifying them could complement existing methods to detect Alzheimer's earlier, without having to do and pay for additional tests," said Associate Professor Nagaendran Kandiah from NTU's Lee Kong Chian School of Medicine (LKCMedicine), who led the study.

Justin Ong, a fifth-year LKCMedicine student and the study's first author, emphasized the importance of early detection. He noted that identifying Alzheimer's sooner gives doctors more time to intervene and potentially slow the progression of symptoms such as memory loss, reduced thinking speed, and mood changes. The research was conducted as part of LKCMedicine's Scholarly Project module in the School's Bachelor of Medicine and Bachelor of Surgery programme.

Why Studying Asian Populations Matters

The study stands out because it focuses on Asian populations, an area that has been underrepresented in Alzheimer's research. Most existing studies have concentrated on Caucasian participants, which may limit how broadly their findings apply.

The NTU team examined nearly 1,000 people in Singapore from different ethnic backgrounds that reflect the country's population. Participants included individuals with normal cognitive function as well as those experiencing mild thinking difficulties.

Research has shown that dementia does not affect all ethnic groups in the same way, making region specific studies essential.

"For example, among Caucasians with dementia, past studies show that the prevalence of a major risk gene, apolipoprotein E4, linked to Alzheimer's is around 50 to 60 percent. But among Singapore dementia patients, it is less than 20 percent," said Assoc Prof Kandiah, who is also Director of the Dementia Research Centre (Singapore) in LKCMedicine. Because of these differences, findings in one population may not directly apply to another.

How the Brain Clears Toxic Waste

Inside the brain, blood vessels are surrounded by small channels called perivascular spaces. These spaces help drain toxic waste products, including beta amyloid and tau proteins, which are found in high levels in people with Alzheimer's disease.

When the brain's waste removal system becomes less efficient, these spaces can enlarge and become visible on MRI scans. Until now, it was unclear whether this change was directly linked to dementia, particularly Alzheimer's disease.