Effects of sex, educational background, and chronic kidney disease grading on longitudinal cognitive and functional decline in patients in the Japanese Alzheimer's Disease Neuroimaging Initiative study

Single-Index Measurement Error Jump Regression Model in Alzheimer's Disease Studies

Alzheimer's disease (AD) is the major cause of dementia in the elderly, and investigations on the impact of risk factors on neurocognitive performance are crucial in preventative treatment. While existing statistical regression models, such as single-index models, have proven effective tools for uncovering the relationship between the neurocognitive scores and covariates of interest such as demographic information, clinical variables, and neuroimaging features, limited research has explored scenarios where jump discontinuities exist in the regression patterns and the covariates are unobservable but measured with errors, which are common in real applications. To address these challenges, we propose a single-index measurement error jump regression model (SMEJRM) that can handle both jump discontinuities and measurement errors in image covariates introduced by different image processing software. This development is motivated by data from 168 patients in the Alzheimer's Disease Neuroimaging Initiative. We establish both the estimation procedure and the corresponding asymptotic results. Simulation studies are conducted to evaluate the finite sample performance of our SMEJRM and the estimation procedure. The real application reveals that jump discontinuities do exist in the relationship between neurocognitive scores and some covariates of interest in this study.

Uremic Toxins, CKD, and Cognitive Dysfunction

Cognitive impairment involves alterations to one's cognitive status that affects everyday life. Individuals with CKD, and particularly kidney failure, experience higher rates of cognitive impairment (20%-70%) compared with the general population. The highest prevalence is described in kidney failure such that dialysis-dependent patients have twice the prevalence of age-matched controls. In the past 5 years, the number of investigations examining the "kidney-brain axis," mechanisms of CKD-related cognitive impairment, and potential therapeutics have exponentially increased. This review article summarizes recent literature on direct and indirect effects of CKD-associated cognitive impairment with emphasis on uremic toxins; brain injury mechanisms; overlap between CKD-associated cognitive impairment, Alzheimer's disease, and other neurodegenerative diseases. Reviewed therapeutic interventions include AST-120 (indoxyl sulfate absorbent), CH-223191 (aryl hydrocarbon receptor antagonist), triarylmethane-34 (Kca3.1-specific inhibitor), anakinra (IL-1R inhibitor), marimastat, exercise, supplements, and kidney transplantation. Special focus is placed on translational studies examining uremic toxin-associated pathogenic processes, including brain oxidative stress, neuroinflammation, and blood-brain barrier dysfunction through in vitro and in vivo models of CKD-associated brain injury. Finally, future research directions are suggested, including targeting of cellular senescence abundance with senotherapeutics and capitalizing on anti-inflammatory effects of regenerative, cell-based therapeutics ( e.g ., mesenchymal stem cells and extracellular vesicles), and use of aged murine models. Collectively, CKD-associated cognitive impairment represents a prevalent condition for which remaining knowledge gaps exist, and scientific advancements are needed to preserve cognitive function and improve the lives of individuals with CKD.

Activity level by clinical severity and sex differences in patients with Alzheimer disease and mild cognitive impairment

BACKGROUND

To determine how to maintain activity in persons with dementia and mild cognitive impairment, we examined the daily activity level by different degrees of clinical severity and sex differences in patients with Alzheimer's disease and mild cognitive impairment.

METHODS

This study included 92 patients with Alzheimer's disease and 33 patients with mild cognitive impairment who visited our rehabilitation department. The Frenchay Activities Index was used to assess the level of activity.

RESULTS

Women had high Frenchay Activities Index scores for household activities, such as meal preparation, washing clothes, and light housework, whereas men had high Frenchay Activities Index scores for social occasions and walking outside. Although activity decreased with the severity of dementia in women, there was no difference in men. Additionally, a negative correlation was observed between the number of people living together and activity in women.

CONCLUSIONS

To maintain and improve activities in persons with Alzheimer's disease and mild cognitive impairment, it is important to suggest activities that fit the lifestyle of the individual and family caregivers and to provide lifestyle instructions that consider sex differences.

Gender-specific factors associated with the Japanese version of the trail making test among Japanese workers

[Purpose] The Trail Making Test is a valuable tool for predicting the transition from mild cognitive impairment to dementia. This cross-sectional study aimed to investigate gender-specific factors associated with the Trail Making Test using body composition and motor function among Japanese workers. [Participants and Methods] Demographic data, body composition, motor function, and cognitive and attentional functions (Trail Making Test, Part B) were analyzed among 627 workers who underwent health assessments during the 2019 fiscal year. After conducting univariate analysis, multiple regression analysis was performed. [Results] The presence of metabolic syndrome risk factors was found to significantly prolonged the performance time of the Trail Making Test-B in male workers. In addition, low fat-free mass and the 30-second chair stand test also significantly prolonged the performance time of the Trail Making Test-B in male workers. Among female workers, the presence of metabolic syndrome risk factors affected the performance time of the Trail Making Test-B. Therefore, MetS risk factors affect the performance times of the Trail Making Test-B in both male and female workers. [Conclusion] As male and female workers exhibit different body composition and motor function items in the Trail Making Test-B, gender differences should be considered when formulating measures to prevent cognitive and attentional decline.

Predictors of probable attention deficit hyperactivity disorder in elderly patients with mild cognitive impairment visiting a memory clinic

Aim

Characteristics of attention deficit hyperactivity disorder (ADHD) that persist into old age are often confused with symptoms of mild cognitive impairment (MCI), and the actual rate of probable ADHD in people with MCI is unknown. This study estimated the proportion of MCI patients with probable ADHD and investigated the factors to identify MCI patients with probable ADHD.

Methods

We recruited 36 elderly patients (11 males, 25 females, mean age 72.4 ± 7.6 years) who met the MCI criteria. The MCI patients were classified as those with [MCI/ADHD (+)] and without [MCI/ADHD (-)] probable ADHD, according to the Wender Utah Rating Scale scores. The autism features, inattention, and hyperactivity features during childhood and current periods, estimated intelligence quotient, and demographic data were compared between the groups. Multiple logistic regression analysis was performed to identify factors of MCI/ADHD (+) patients.

Results

Nine (25.0%) and 27 patients were added into the MCI/ADHD (+) and MCI/ADHD (-) groups, respectively. The MCI/ADHD (+) group mostly comprised men, those who visited the clinic at a younger age, had more years of schooling, and had strong autism spectrum disorder tendencies. Multiple logistic regression analysis indicated male sex and current hyperactivity as significant predictors of probable ADHD in MCI patients.

Conclusion

A quarter of the patients with MCI had probable ADHD. Male sex and hyperactivity at the time of MCI diagnosis might help in predicting probable ADHD in MCI patients. However, these results were obtained from a single-center, small-case study and should be confirmed via longitudinal studies with a large number of cases.

Estimating the longitudinal trajectory of cognitive function measurement using short-term data with different disease stages: Application in Alzheimer's disease

Alzheimer's disease (AD) is a chronic neurodegenerative disease characterized by a gradual decline in cognitive function over a few decades. The Mini-Mental State Examination (MMSE) is a widely used measure for evaluating global cognitive functioning. Characterizing the longitudinal trajectory of the MMSE in the population of interest is important to detect AD onset for preventive intervention. In this study, we formulate a new class of longitudinal trajectory modeling for MMSE from short-term individual data based on an ordinary differential equation. The proposed method models the relationship between individual decline speed of MMSE and the average MMSE using the fractional polynomial function model and subsequently estimates the longitudinal trajectory of MMSE by solving the ordinary differential equation for the estimated model. The appropriate model for trajectory estimation is selected based on the proposed criterion for quantifying the goodness of trajectory fit. The accuracy of the trajectory estimation of the proposed method was demonstrated via simulation studies. The proposed method was successfully applied to MMSE data from the Japanese Alzheimer's Disease Neuroimaging Initiative study.

Estimation of Human Cerebral Atrophy Based on Systemic Metabolic Status Using Machine Learning

Background

Based on the assumption that systemic metabolic disorders affect cognitive function, we have developed a deep neural network (DNN) model that can estimate cognitive function based on basic blood test data that do not contain dementia-specific biomarkers. In this study, we used the same DNN model to assess whether basic blood data can be used to estimate cerebral atrophy.

Methods

We used data from 1,310 subjects (58.32 ± 12.91years old) enrolled in the Brain Doc Bank. The average Mini Mental State Examination score was 28.6 ± 1.9. The degree of cerebral atrophy was determined using the MRI-based index (GM-BHQ). First, we evaluated the correlations between the subjects' age, blood data, and GM-BHQ. Next, we developed DNN models to assess the GM-BHQ: one used subjects' age and blood data, while the other used only blood data for input items.

Results

There was a negative correlation between age and GM-BHQ scores (r = -0.71). The subjects' age was positively correlated with blood urea nitrogen (BUN) (r = 0.40), alkaline phosphatase (ALP) (r = 0.22), glucose (GLU) (r = 0.22), and negative correlations with red blood cell counts (RBC) (r = −0.29) and platelet counts (PLT) (r = −0.26). GM-BHQ correlated with BUN (r = −0.30), GLU (r = −0.26), PLT (r = 0.26), and ALP (r = 0.22). The GM-BHQ estimated by the DNN model with subject age exhibited a positive correlation with the ground truth GM-BHQ (r = 0.70). Furthermore, even if the DNN model without subject age was used, the estimated GM-BHQ showed a significant positive correlation with ground truth GM-BHQ (r = 0.58). Age was the most important variable for estimating GM-BHQ.

Discussion

Aging had the greatest effect on cerebral atrophy. Aging also affects various organs, such as the kidney, and causes changes in systemic metabolic status, which may contribute to cerebral atrophy and cognitive impairment. The DNN model may serve as a new screening test for dementia using basic blood tests for health examinations. Finally, the blood data reflect systemic metabolic disorders in each subject—this method may thus contribute to personalized care.

Quality of life and cognitive assessment in healthy older Asian people with early and moderate chronic kidney disease: The NAHSIT 2013–2016 and validation study

Background

Taiwan has the highest prevalence of chronic kidney disease (CKD). Impaired cognition and quality of life are significant phenomena in the late stages of CKD. We sought to obtain an overview and the attributable effect of impaired glomerular filtration on multiple domains in cognition and dimensions of quality of life for community-based healthy older adults in Taiwan.

Methods

The study was derived from the Nutrition and Health Survey in Taiwan (NAHSIT) 2013–2016, a nationwide cross-sectional study conducted to sample healthy, community-based older adults aged ≥65 years in Taiwan. Participants were categorized into four CKD groups: CKD stage 1, stage 2, stages 3a and 3b, and stages 4–5. The Mini-Mental State Examination (MMSE) and the QoL questionnaire derived from the 12-item Short Form Health Survey (SF-12) were measured. Generalized linear mixed models (GLMMs) and principal component regressions were employed for the analysis and validation, respectively.

Results

Participants with moderate CKD (stages 3a and 3b) showed deficits in global MMSE, domain orientation to time, calculation, complex commands, and role-physical and vitality in QoL questionnaires. In GLMMs, impaired eGFR per 30 mL/min/1.73 m² was associated with lower global MMSE scores (β = -0.807, standard error [SE] = 0.235, P = 0.0007), domain orientation to time (β = -0.155, SE = 0.047, P = 0.0011), calculation (β = -0.338, SE = 0.109, P = 0.0020), complex commands (β = -0.156, SE = 0.079, P = 0.0494), and role-physical (β = -2.219, SE = 0.779, P = 0.0046) dimensions of QoL.

Conclusions

Elderly Han Chinese adults with moderately impaired renal filtration could manifest cognitive deficits in orientation to time, calculation, and impaired quality of life in physical role functioning.

Disentangling the Relationship Between Chronic Kidney Disease and Cognitive Disorders

Chronic kidney disease (CKD) is a rapidly rising global health burden that affects nearly 40% of older adults. Epidemiologic data suggest that individuals at all stages of chronic kidney disease (CKD) have a higher risk of developing cognitive disorders and dementia, and thus represent a vulnerable population. It is currently unknown to what extent this risk may be attributable to a clustering of traditional risk factors such as hypertension and diabetes mellitus leading to a high prevalence of both symptomatic and subclinical ischaemic cerebrovascular lesions, or whether other potential mechanisms, including direct neuronal injury by uraemic toxins or dialysis-specific factors could also be involved. These knowledge gaps may lead to suboptimal prevention and treatment strategies being implemented in this group. In this review, we explore the mechanisms of susceptibility and risk in the relationship between CKD and cognitive disorders.

Selenium concentrations in elderly people with Alzheimer's disease: a cross-sectional study with control group

OBJECTIVE

To investigate possible differences in plasma and erythrocyte concentrations of selenium among elderly with and without a diagnosis of Alzheimer's disease (AD).

METHODS

Cross-sectional study, performed with an elderly group with Alzheimer's disease, diagnosed by a geriatric doctor, and compared to an elderly group without the disease, equaling gender, education, and age. Atomic absorption spectrophotometry determined plasma and erythrocyte concentrations of total selenium (Set).

RESULTS

The mean age was 74.41±7.1 years in the Alzheimer's disease group and 71.46±5.1 years among the control group. The Alzheimer's disease group presented lower plasma concentrations (mean of 45.29±14.51 µg/dL vs. 55.14±14.01 µg/dL; p=0.004), and erythrocyte Set (median of 56.36 µg/L vs. 76.96 µg/L; p<0.001). The logistic regression model indicated an association between erythrocyte Set concentrations and diagnosis of Alzheimer's disease (p=0.028).

CONCLUSION

Elderly with Alzheimer's disease present lower selenium concentrations in the evaluated organic compartments.

Sex differences and the role of education in cognitive ageing: analysis of two UK-based prospective cohort studies

BACKGROUND

Previous studies have shown an excess risk of Alzheimer's disease and related dementias among women. Education is thought to have a causal association with dementia onset. We aimed to investigate the role of education in influencing sex differences in cognitive ageing.

METHODS

We analysed data from two prospective cohort studies in the UK; the English Longitudinal Study of Ageing (ELSA) and the Whitehall II study, to assess sex differences in cognitive performance and cognitive decline by birth cohort (birth year 1930-38, 1939-45, or 1946-55), before and after adjustment for education, and by high and low education level. Memory was assessed using immediate recall, for which data were available from all waves of the ELSA (2002-14) and Whitehall II (1997-2015) studies. Fluency was assessed using a semantic fluency test based on an animal naming task, with data available from all waves of the Whitehall II study and waves one to five (2002-10) and wave seven (2014) of the ELSA study. Cognitive scores were standardised separately in each study based on the mean and SD of the corresponding test among participants aged 50-59 years with secondary education.

FINDINGS

15 924 participants were included from the two studies. In pooled analyses, women had better memory scores than men in all birth cohorts, irrespective of adjustment for education (eg, at age 60 years, birth cohort 1930-38, mean difference between sexes [male scores minus female scores] -0·25 SDs [95% CI -0·32 to -0·19] after adjustment for education), and in both education level groups. Memory decline was faster in men than in women (at age 60 years, birth cohort 1946-55, mean difference in 13-year change -0·15 SDs [-0·20 to -0·09]; after adjustment for education -0·14 SDs [-0·20 to -0·08]). Men had better fluency scores than women in earlier birth cohorts and in the low education group (at age 60 years, birth cohort 1930-38, mean difference 0·20 SDs [95% CI 0·05 to 0·36]); but women had better fluency scores than men in later birth cohorts and in the high education group (at age 60 years, birth cohort 1946-55, mean difference -0·17 SDs [-0·24 to -0·10]). No sex differences were observed for fluency decline.

INTERPRETATION

Our findings suggest that decreasing disparities between sexes in education, due to secular increases in educational opportunities, could attenuate sex differences in dementia risk and cognitive decline in the future.

FUNDING

National Institute on Aging, National Institutes of Health; UK Medical Research Council; British Heart Foundation; and National Institute for Health Research.

Disabilities of the arms, pinch strength, and mild cognitive impairment in patients with coronary artery disease

BACKGROUND

We aimed to examine the relationship between the difficulty of activity using the arms and mild cognitive impairment (MCI), the relationship between the difficulty of activity using the arms and manual function, and cognitive function in patients with coronary artery disease (CAD).

METHODS

We conducted a cross-sectional study of 263 non-dementia patients who met the study criteria from 2328 CAD patients. MCI was estimated with the Japanese version of the Montreal Cognitive Assessment (MoCA-J). The difficulty of activity using the arms was evaluated using the Disability of the Arm, Shoulder, Disability of the Arm, Shoulder and Hand and Hand (DASH) questionnaire. Manual function was evaluated by pinch strength and handgrip strength.

RESULTS

Age (odds ratio, 1.10), three-fingered pinch strength (odds ratio, 0.69), and DASH score (odds ratio, 1.03) were independently associated with MCI in the multivariable logistic regression analysis. Hemoglobin (β=-0.15), handgrip strength (β=-0.37), and MoCA-J score (β=-0.15) were independently associated with DASH score (Model 1: p<0.001, adjusted R²=0.33); hemoglobin (β=-0.17), eGFR (β=-0.14), three-fingered pinch strength (β=-0.25), and MoCA-J score (β=-0.14) were independently associated with DASH score in the multivariate regression analysis (Model 2: p<0.001, adjusted R²=0.31).

CONCLUSIONS

The difficulty of activity using the arms was independently associated with manual and cognitive function and MCI in CAD patients.

Gait speed, life-space mobility and mild cognitive impairment in patients with coronary artery disease

Slow gait speed and restricted life-space mobility predict cognitive decline and dementia in healthy older adults, yet the relation between gait speed or life-space mobility and cognitive function remains poorly understood in patients with coronary artery disease (CAD). We, therefore, examined the following relations: that between gait speed and cognitive function, and mild cognitive impairment (MCI) and that between life-space mobility and cognitive function, and MCI. We conducted a cross-sectional study of 240 non-dementia patients who met the study criteria from 2132 consecutive CAD patients. MCI was estimated with the Japanese version of the Montreal Cognitive Assessment (MoCA-J). Gait speed was measured to perform gait trials at the patients' usual walking pace, and life-space mobility was evaluated using the Life-Space Assessment (LSA). We investigated the relation between gait speed or life-space mobility and cognitive function by Pearson correlation analysis, whereas multivariable logistic regression analysis was conducted for detecting MCI. Gait speed and LSA scores were positively associated with the MoCA-J score (r = 0.54, p < 0.001 and r = 0.44, p < 0.001, respectively), and both were independently associated with MCI in the multivariable logistic regression analysis (odds ratio 0.007, p < 0.001, and odds ratio 0.98, p = 0.038, respectively). Cognitive impairment can be easily detected by assessment of gait speed and life-space mobility. Interventions to improve gait speed and life-space mobility may lead to the improvement of cognitive function and MCI in patients with CAD.

Lower Serum Calcium as a Potentially Associated Factor for Conversion of Mild Cognitive Impairment to Early Alzheimer's Disease in the Japanese Alzheimer's Disease Neuroimaging Initiative

BACKGROUND

Effect of serum calcium level to the incidence of mild cognitive impairment (MCI) conversion to early Alzheimer's disease (AD) remains uncertain.

OBJECTIVE

To investigate association between baseline serum calcium and the MCI conversion in the Japanese Alzheimer's Disease Neuroimaging Initiative (J-ADNI) study cohort.

METHODS

In this sub-analysis of J-ADNI study, we reviewed data from MCI participants at baseline regarding their conversion to early AD during the 3 years of observation period and assessed the associated factors including serum calcium level. In addition, we compared our results from the J-ADNI study with the corresponding results from the North American (NA)-ADNI.

RESULTS

Of 234 eligible MCI participants from the J-ADNI cohort, 121 (51.7%) converted to AD during the first 36 months of observation. Using univariate analysis, being female, having shorter years of education, and lower serum calcium level were correlated with increased risk of MCI-to-AD conversion exclusively in J-ADNI cohort. The lower corrected serum calcium level remained as one of conversion-associated factors in the J-ADNI cohort even after adjustment for multiple confounding variables, although this was not observed in the NA-ADNI cohort.

CONCLUSION

Our findings suggest that lower serum calcium may be associated with an increased risk of MCI conversion to AD in Japanese cohorts. The reason for this correlation remains unclear and further external validation using other Asian cohorts is needed. It would be interesting for future AD studies to obtain serum calcium levels and other related factors, such as vitamin D levels, culture-specific dietary or medication information.

Serum concentration of dihomo-γ-linolenic acid is associated with cognitive function and mild cognitive impairment in coronary artery disease patients

BACKGROUND

The relation between levels of n-6 polyunsaturated fatty acids (PUFAs) and cognitive function and mild cognitive impairment (MCI) in patients with coronary artery disease (CAD) is unclear. The purpose of the present study was to examine the associations between levels of n-6 PUFAs and cognitive function and MCI in patients with CAD.

METHODS

We conducted a cross-sectional study of 129 patients with CAD but without probable dementia. MCI was estimated with the Japanese version of the Montreal Cognitive Assessment (MoCA-J). We classified patients into the normal cognitive group and MCI group and compared their clinical characteristics and serum levels of PUFAs. The relation between these levels and cognitive function and MCI was clarified with Pearson correlation analysis and logistic regression analysis.

RESULTS

The serum levels of dihomo-γ-linolenic acid (DGLA) in the CAD patients with MCI were significantly lower than those in the patients with normal cognitive function (p= 0.04). The serum levels of DGLA were positively associated with the MoCA-J score (r= 0.24, p= 0.005) and significantly associated with MCI in the univariate logistic regression analysis (odds ratio, 0.97; p= 0.035). However, in the multivariate logistic regression analysis, only age was significantly associated with MCI (odds ratio, 1.11; p < 0.001).

CONCLUSIONS

The serum levels of DGLA were associated with cognitive function and MCI in patients with CAD. Although not an independent predictor, DGLA might be one useful marker with which to identify early cognitive decline in these patients.

Relation of Poor Nutritional Status to Mild Cognitive Impairment in Patients with Coronary Artery Disease

OBJECTIVES

Nutritional status affects cerebral circulation and cognitive function. More attention needs to be paid to nutritional status in coronary artery disease (CAD) patients, yet the relation between nutritional status or dietary intake (DI) and cognitive function or mild cognitive impairment (MCI) in CAD patients remain unclear. Thus, we examined the following relations: 1) that between nutritional status and cognitive function, and MCI and 2) that between DI and cognitive function, and MCI.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a cross-sectional study of 208 patients with CAD but without dementia.

MEASUREMENTS

MCI was estimated with the Japanese version of the Montreal Cognitive Assessment (MoCA-J). Nutritional status was assessed by the Geriatric Nutritional Risk Index (GNRI), and DI was assessed by total energy intake per day. We investigated the relation between nutritional status or DI and cognitive function by Pearson correlation analysis, and that between nutritional status or DI and MCI by multivariable logistic regression analysis.

RESULTS

The GNRI and DI were positively associated with the MoCA-J score (r = 0.23, p < 0.001, and r = 0.24, p < 0.001, respectively), and both were independently associated with MCI in the multivariable logistic regression analysis (odds ratio, 0.96; p = 0.045, and odds ratio, 0.998; p = 0.020, respectively).

CONCLUSIONS

Poor nutritional status and low DI were found to be significantly associated with cognitive function and MCI in CAD patients. Our findings regarding nutritional status and DI might be useful for clinicians to prevent or intervene in the early cognitive decline of inpatients with CAD.

Links between Cognitive Status and Trace Element Levels in Hair for an Environmentally Exposed Population: A Case Study in the Surroundings of the Estarreja Industrial Area

In the present study, trace elements (TE) levels were evaluated in scalp hair along the continuum from healthy subjects (HS) to patients suffering from subjective memory concerns (SMC), and/or mild cognitive impairment (MCI), and those with already installed dementia (DEM) in order to: (i) assess the effects of environmental and lifestyle factors on TE concentrations and (ii) evaluate the analyzed elements as possible diagnostic biomarkers for the disease. The study involved 79 mainly permanent residents, >55 years old, from the city of Estarreja (northern Portugal), a former industrial area. The health status of the participants was assessed by means of a complete socio-demographic questionnaire and through cognitive screening tests, namely the Mini-Mental State Examination (MMSE). The test scores were categorized and used in the statistical analysis. Hair samples were collected and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) ICP-MS for selected TE. Dementia appears to be associated with higher age, the female gender, lower education level, and longer residence time in the study area. In addition, most of the participants diagnosed with dementia frequently consume home-grown foodstuffs, some irrigated with contaminated well water. The calculation of the TE enrichment factors of soil samples collected in kitchen gardens/small farms in the vicinity of the Estarreja Chemical Complex (ECC) reinforces the degree of Hg soil contamination in the area, due to anthropogenic sources that can be a source for the population Hg exposure route among others. Mercury levels in hair differed significantly between the four individual groups (HS, SMC, MCI, and DEM), increasing from healthy to dementia participants. Improved diagnostic results can be obtained using hair TE signatures coupled with MMSE scores. This strategy may prove useful for predictive diagnosis in population screening for cognitive impairment.

Visualizing modules of coordinated structural brain atrophy during the course of conversion to Alzheimer's disease by applying methodology from gene co-expression analysis

Objective

We aimed to identify modularized structural atrophy of brain regions with a high degree of connectivity and its longitudinal changes associated with the progression of Alzheimer's disease (AD) using weighted gene co-expression network analysis (WGCNA), which is an unsupervised hierarchical clustering method originally used in genetic analysis.

Methods

We included participants with late mild cognitive impairment (MCI) at baseline from the Japanese Alzheimer's Disease Neuroimaging Initiative (J-ADNI) study. We imputed normalized and Z-transformed structural volume or cortical thickness data of 164 parcellated brain regions/structures based on the calculations of the FreeSurfer software. We applied the WGCNA to extract modules with highly interconnected structural atrophic patterns and examined the correlation between the identified modules and clinical AD progression.

Results

We included 204 participants from the baseline dataset, and performed a follow-up with 100 in the 36-month dataset of MCI cohort participants from the J-ADNI. In the univariate correlation or variable importance analysis, baseline atrophy in temporal lobe regions/structures significantly predicted clinical AD progression. In the WGCNA consensus analysis, co-atrophy modules associated with MCI conversion were first distributed in the temporal lobe and subsequently extended to adjacent parietal cortical regions in the following 36 months.

Conclusions

We identified coordinated modules of brain atrophy and demonstrated their longitudinal extension along with the clinical course of AD progression using WGCNA, which showed a good correspondence with previous pathological studies of the tau propagation theory. Our results suggest the potential applicability of this methodology, originating from genetic analyses, for the surrogate visualization of the underlying pathological progression in neurodegenerative diseases not limited to AD.

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Applying origin-of-genetic unsupervised clustering to structural MRI from J-ADNI.

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We identified highly-interconnected modules associated with AD progression.

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Extension of co-atrophy modules corresponded with tau propagation theory in AD.

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This method has potential for visualizing underlying pathological progression.

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Application to other neurodegenerative diseases not limited to AD is expected.