A groundbreaking study from the Chinese University of Hong Kong demonstrates the potential of functional near-infrared spectroscopy (fNIRS) as a non-invasive tool to identify individuals at risk for dementia, specifically those with mild cognitive impairment (MCI) and subjective memory complaints (SMC). Published in Alzheimer's & Dementia, the research reveals distinct patterns of brain activation that could enable earlier detection in Alzheimer's.

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The study involved 151 participants aged 50 and above, categorized into groups based on cognitive assessments: normal cognition (NC, n=37), mild SMC (n=24), moderate SMC (n=33), severe SMC (n=29), amnestic MCI (aMCI, n=15), and non-amnestic MCI (naMCI, n=13). Using fNIRS to measure prefrontal hemodynamics during a visual memory span task—where participants memorized and reproduced sequences of colored blocks—researchers observed significantly lower oxyhemoglobin (HbO) levels in the aMCI group compared to NC, indicating reduced brain activation. Similarly, individuals with severe SMC showed lower HbO levels than those with NC, mild SMC, or moderate SMC. No significant differences were found in the naMCI group.

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Receiver operating characteristic (ROC) analysis highlighted fNIRS's diagnostic potential, achieving 69.23% accuracy in distinguishing aMCI from NC and 69.70% accuracy for severe SMC from NC. These findings were supported by correlations between HbO levels and performance on memory assessments, underscoring fNIRS's sensitivity to early cognitive changes.

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"Early identification of at-risk individuals is key to slowing dementia's impact, and fNIRS offers a cost-effective, portable alternative to traditional imaging methods," said Professor Agnes S. Chan, corresponding author and Director of the Research Center for Neuropsychological Well-Being at CUHK.

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She further added, "Our results emphasize that not all MCI subtypes show the same brain patterns, with amnestic cases linked more closely to Alzheimer's risk. fNIRS provides objective insights beyond self-reported symptoms, paving the way for targeted prevention strategies."

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Conducted at CUHK's Neuropsychology Laboratory, the study addresses the growing global dementia burden, affecting over 55 million people, by focusing on MCI (prevalence ~15.56% in those over 50) and SMC (affecting 50-63% of older adults). Limitations include the sample's focus on Chinese-speaking participants and the need for validation in larger, diverse cohorts. The research was funded internally by CUHK and builds on efforts to advance non-invasive biomarkers for cognitive health.

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Lee, T. L., Guo, L., & Chan, A. S. (2024). fNIRS as a biomarker for individuals with subjective memory complaints and MCI. Alzheimer's & Dementia, 20(8), 5170-5182. https://doi.org/10.1002/alz.13897