Factors that affect the health of blood vessels, such as high blood pressure or diabetes, are common in older adults. These factors can contribute to brain damage and are associated with a future risk of stroke and dementia. This brain damage can appear on scans as areas called white matter hyperintensities. However, how common these risk factors are across different types of neurodegenerative diseases and how they relate to brain damage in those specific conditions has not been fully studied.
This study investigated the link between the total burden of vascular risk factors and the health of the brain's white matter. The research looked at individuals with five different neurodegenerative conditions.
The study included 520 participants from a larger Canadian research project. The groups consisted of 126 people with amnestic Mild Cognitive Impairment or Alzheimer’s Disease, 53 with Frontotemporal Dementia, 161 with Cerebrovascular Disease (a condition related to blood flow in the brain), 140 with Parkinson’s Disease, and 40 with Amyotrophic Lateral Sclerosis. A comparison group of 41 cognitively healthy adults was also included.
Researchers calculated a vascular risk score for each person, on a scale from 0 to 5. This score was based on the presence of five factors: high blood pressure, diabetes, unhealthy cholesterol levels, obesity, and a history of smoking. The health of the brain's white matter, which is the network of nerve fibers connecting brain regions, was measured using MRI scans. They looked at both large-scale damage (the volume of white matter hyperintensities) and the smaller, microscopic structure of the white matter. The analysis was adjusted for age, sex, education, and the presence of a gene variant (APOE ε4) associated with Alzheimer's disease.
The results showed that vascular risk factors, particularly high blood pressure and high cholesterol, were more common in the groups with a neurodegenerative disease than in the healthy control group. A higher vascular risk score was associated with a higher likelihood of being in the Mild Cognitive Impairment/Alzheimer’s Disease group (1.5 times more likely), the Frontotemporal Dementia group (1.7 times more likely), and the Cerebrovascular Disease group (2.6 times more likely).
When all participants were analyzed together, a high vascular risk score was linked to poorer white matter health, both in its large-scale appearance and its microscopic structure. When the disease groups were analyzed separately, this link was specifically found in the group with Cerebrovascular Disease. The presence of the APOE ε4 gene only slightly reduced the strength of these connections.
The study concludes that having a high burden of vascular risk factors is common among individuals with conditions like Mild Cognitive Impairment/Alzheimer’s Disease, Frontotemporal Dementia, and Cerebrovascular Disease. This risk burden also affects the health of the brain's white matter. The authors suggest that future studies are needed to see if managing these vascular risk factors might lessen the consequences of brain degeneration in these groups.
