Monitoring rate of decline in brain activity may help doctors to arrest dementia at its early stages
Differential changes in brain functional network connectivity can differentiate Alzheimer’s disease and cerebrovascular disease, allowing doctors to diagnose dementia at its early stages.
SINGAPORE | 17 September 2019
A general trend of increasing life expectancy and declining fertility rates has recast the roles elderly workers play in the economy. Having amassed a wealth of knowledge and experience under their belts, many employers are turning to older workers as a crucial solution to manpower needs. More elderly are rising up to the challenge and working through their twilight years, however, the increasing prevalence of dementia threatens to disrupt the current workforce dynamic.
Arresting dementia at its early stages is crucial to enabling elderly workers to continue contributing to our economy, yet it is easier said than done. Currently, the diagnosis of dementia in primary care is dependent mostly on clinical suspicion based on patient symptoms or caregivers’ concerns and is prone to be missed or delayed. However, a recent discovery sets the scene for a revolutionised treatment option which enables cognitive impairments which can cause dementia to be identified and subsequently treated even before one develops dementia.
Dementia is an umbrella term used to describe symptoms that affects mental cognitive tasks such as memory and reasoning. Dementia is caused by underlying diseases, most commonly Alzheimer’s disease, when beta-amyloid deposition and neurofibrillary tangles lead to loss of synapses and neurons, resulting in gross atrophy of the affected areas of the brain, and cerebrovascular disease, when haemorrhages in the brain occur, reducing blood supply to brain cells and causing brain cell death.
Previously, researchers from Duke-NUS, Sungkyunkwan University School of Medicine and Ulsan School of Medicine revealed that Alzheimer’s disease and cerebrovascular disease have distinct effects on the functional connectivity (interaction between neurons) of various brain networks in the brain. Alzheimer’s disease can be characterised by a decline in functional connectivity in the default mode network (DMN), which is linked to memory function and prediction of future events. Meanwhile, cerebrovascular disease is distinguished by disruptions in the executive control network (ECN), which is linked to cognitive control of behaviour, such as attention control.
In the research team’s most recent study, they aim to examine the associations between pathological markers of these diseases and longitudinal changes in the functional connectivity of these networks, greatly facilitating diagnosis of these diseases in the early stages.
The participants for the study included people with mild cognitive impairment who suffered symptoms such as memory problems, considered to be an early sign of Alzheimer’s disease, and people with mild cognitive impairment with damage to small blood vessels in the brain, an early sign of dementia due to cerebrovascular disease. During the study, the participants took position emission tomography (PET) scans to check if their brains contained amyloid-beta plaques, hard, insoluble accumulations of beta amyloid proteins that clump together between neurons -- a hallmark of Alzheimer’s disease. The participants also took functional MRI (fMRI) scans which measured changes in brain functional network connectivity. Participants were followed up clinically with annual MRI for up to 4 years.
The results showed that participants who were in the early stages of Alzheimer’s disease had a more drastic decrease in extent of interactions between neurons in the DMN over time, as compared to the participants in the early stages of vascular dementia. The rate of annual decline in DMN connections was on average 13.6 times faster in the people with Alzheimer’s disease marker than in those without. Similarly, the participants in early stages of vascular dementia had on average three times higher a rate of annual increase in interactions in the ECN than those in the early stages of Alzheimer’s disease.
A total of 85 participants were recruited from Samsung Medical Centre and Sungkyunkwan University school of Medicine for this study. “More studies are needed with larger numbers of participants and longer follow-up periods,” Said Associate Professor Sang Won Seo, senior and corresponding author of the study from Samsung Medical Centre, acknowledging that more steps can be taken for more accurate findings. “But these results suggest that these changes in brain network connections could potentially be used to track early changes in Alzheimer’s disease and cerebrovascular disease.” Indeed, these findings can revolutionise dementia diagnosis and treatment, aiding doctors in tracking early differential disease progression and predict future cognitive decline long before patients develop dementia.
Moving forward, the researchers will examine the additive and interactive effects of amyloid-beta, tau proteins (another marker of Alzheimer’s disease), and specific types of cerebrovascular lesions on brain functional networks in cognitively normal and mild impairment individuals to better facilitate prognosis and treatment planning.
The research paper was published in September 2019 on Neurology.
This article was contributed by Michelle Tan Min Shuen, an editorial intern at World Scientific Publishing Co. and a contributing writer for Asia-Pacific Biotech News. She is from Nanyang Girls' High School, has a keen interest in chemistry and the life sciences, and pursues taekwondo in her free time.