Chinese Preclinical Alzheimer's Disease Study (C-PAS): Design and Challenge from PET Acceptance

fNIRS as a biomarker for individuals with subjective memory complaints and MCI

INTRODUCTION

Identifying individuals at risk of developing dementia is crucial for early intervention. Mild cognitive impairment (MCI) and subjective memory complaints (SMCs) are considered its preceding stages. This study aimed to assess the utility of functional near-infrared spectroscopy (fNIRS) in identifying individuals with MCI and SMC.

METHODS

One hundred fifty-one participants were categorized into normal cognition (NC); amnestic MCI (aMCI); non-amnestic MCI (naMCI); and mild, moderate, and severe SMC groups. Task-related prefrontal hemodynamics were measured using fNIRS during a visual memory span task.

RESULTS

Results showed significantly lower oxyhemoglobin (HbO) levels in aMCI, but not in naMCI, compared to the NC. In addition, severe SMC had lower HbO levels than the NC, mild, and moderate SMC. Receiver operating characteristic analysis demonstrated 69.23% and 69.70% accuracy in differentiating aMCI and severe SMC from NC, respectively.

DISCUSSION

FNIRS may serve as a potential non-invasive biomarker for early detection of dementia.

HIGHLIGHTS

Only amnestic mild cognitive impairment (aMCI), but not non-amnestic MCI, showed lower oxyhemoglobin (HbO) than normal individuals. Reduced HbO was observed in those with severe subjective memory complaints (SMCs) compared to normal cognition (NC), mild, and moderate SMCs. Functional near-infrared spectroscopy measures were associated with performance in memory assessments. Prefrontal hemodynamics could distinguish aMCI and severe SMC from NC.

Pathophysiology characterization of Alzheimer's disease in South China's aging population: for the Greater-Bay-Area Healthy Aging Brain Study (GHABS)

INTRODUCTION

The Guangdong-Hong Kong-Macao Greater-Bay-Area of South China has an 86 million population and faces a significant challenge of Alzheimer's disease (AD). However, the characteristics and prevalence of AD in this area are still unclear due to the rarely available community-based neuroimaging AD cohort.

METHODS

Following the standard protocols of the Alzheimer's Disease Neuroimaging Initiative, the Greater-Bay-Area Healthy Aging Brain Study (GHABS) was initiated in 2021. GHABS participants completed clinical assessments, plasma biomarkers, genotyping, magnetic resonance imaging (MRI), β-amyloid (Aβ) positron emission tomography (PET) imaging, and tau PET imaging. The GHABS cohort focuses on pathophysiology characterization and early AD detection in the Guangdong-Hong Kong-Macao Greater Bay Area. In this study, we analyzed plasma Aβ42/Aβ40 (A), p-Tau181 (T), neurofilament light, and GFAP by Simoa in 470 Chinese older adults, and 301, 195, and 70 had MRI, Aβ PET, and tau PET, respectively. Plasma biomarkers, Aβ PET, tau PET, hippocampal volume, and temporal-metaROI cortical thickness were compared between normal control (NC), subjective cognitive decline (SCD), mild cognitive impairment (MCI), and dementia groups, controlling for age, sex, and APOE-ε4. The prevalence of plasma A/T profiles and Aβ PET positivity were also determined in different diagnostic groups.

RESULTS

The aims, study design, data collection, and potential applications of GHABS are summarized. SCD individuals had significantly higher plasma p-Tau181 and plasma GFAP than the NC individuals. MCI and dementia patients showed more abnormal changes in all the plasma and neuroimaging biomarkers than NC and SCD individuals. The frequencies of plasma A+/T+ (NC; 5.9%, SCD: 8.2%, MCI: 25.3%, dementia: 64.9%) and Aβ PET positivity (NC: 25.6%, SCD: 22.5%, MCI: 47.7%, dementia: 89.3%) were reported.

DISCUSSION

The GHABS cohort may provide helpful guidance toward designing standard AD community cohorts in South China. This study, for the first time, reported the pathophysiology characterization of plasma biomarkers, Aβ PET, tau PET, hippocampal atrophy, and AD-signature cortical thinning, as well as the prevalence of Aβ PET positivity in the Guangdong-Hong Kong-Macao Greater Bay Area of China. These findings provide novel insights into understanding the characteristics of abnormal AD pathological changes in South China's older population.

Neuropsychiatric symptoms in Alzheimer's continuum and their association with plasma biomarkers

BACKGROUND

Little is known about association between neuropsychiatric symptoms and plasma biomarkers across the entire Alzheimer's continuum.

METHODS

A total of 305 individuals with amyloid-β (Aβ) deposition (determined by 18F-florbetapir PET) participated in this study, including cognitively normal controls (n = 53), subjective cognitive decline (SCD, n = 75), mild cognitive impairment (MCI, n = 74), and dementia (n = 103). Plasma biomarkers (Aβ1-42, Aβ1-40, total tau [t-tau], phosphorylated tau 181 [p-tau181], and neurofilament light [NfL]), apolipoprotein E (APOE) genotyping and Neuropsychiatric Inventory Questionnaire (NPI-Q) were completed. Neuropsychiatric symptoms were classified into four subsymdromes (hyperactivity, psychosis, affective, and apathy). Logistic regression analysis was conducted to investigate relationships between neuropsychiatric symptoms and plasma biomarkers.

RESULTS

About one-third of cognitively unimpaired individuals (normal controls: 34.0 %, SCD: 28.0 %) reported one or more neuropsychiatric symptoms, and more in symptomatic stages such as MCI (40.5 %) and dementia (81.0 %). Plasma NfL significantly increased in dementia group compared to SCD and healthy controls, relating to a higher risk of aberrant motor behavior, anxiety, sleep disturbance, disinhibition, and euphoria. Older age (odds ratio [OR] = 1.079, 95 % confidence interval [CI] = 1.022-1.140, p = 0.006), lower cognitive score (OR = 0.846, 95%CI = 0.791-0.905, p < 0.001) and increased plasma NfL (OR = 1.021, 95%CI = 1.00-1.042, p = 0.041) could predict psychosis. No significant differences were found in plasma Aβ1-42/Aβ1-40, t-tau or p-tau181 across all groups, and none correlated with neuropsychiatric symptoms.

LIMITATIONS

The cross-sectional design, small sample size and use of NPI-Q.

CONCLUSIONS

This study supported neuropsychiatric symptoms as early manifestations of preclinical Alzheimer's disease, and suggested plasma NfL to be a potential biomarker for detecting neuropsychiatric symptoms in Alzheimer's continuum.