Cerebral quantitative susceptibility mapping predicts amyloid-β-related cognitive decline

Area of Science:

• Neuroimaging
• Biomarkers of Alzheimer's Disease
• Neurodegeneration

Background:

• Alzheimer's disease (AD) progression varies significantly among individuals with amyloid-β pathology.
• Iron accumulation is a potential co-pathology that may interact with amyloid-β to influence AD progression.
• Quantitative susceptibility mapping (QSM) is an MRI technique sensitive to tissue iron concentration.

Purpose of the Study:

• To investigate the relationship between brain iron levels, amyloid-β load, and cognitive decline in a cohort of Australian Imaging, Biomarkers and Lifestyle (AIBL) study participants.
• To assess if QSM can predict the rate of cognitive deterioration in individuals with and without Alzheimer's disease pathology.

Main Methods:

• 117 participants from the AIBL study underwent baseline MRI and amyloid-β positron emission tomography (PET).
• Cognitive function was assessed every 18 months for up to 6 years in 100 volunteers (cognitively normal, mild cognitive impairment, or AD).
• Quantitative susceptibility mapping (QSM) was used to measure iron levels in brain regions, particularly the hippocampus, temporal lobe, and frontal lobe.

Main Results:

• Among 45 participants with amyloid pathology, higher hippocampal QSM levels significantly predicted accelerated decline in episodic memory, executive function, and attention.
• Higher QSM levels in the temporal and frontal lobes predicted deteriorating language test performance.
• These associations remained significant even after accounting for amyloid-β load.

Conclusions:

• Brain iron accumulation, as measured by QSM, may synergize with amyloid-β pathology to accelerate cognitive decline in Alzheimer's disease.
• QSM, in conjunction with amyloid-β PET, shows potential for stratifying individuals at higher risk of rapid cognitive deterioration.
• This research highlights the role of iron as a critical factor in modulating Alzheimer's disease progression.