Association and interaction of TOMM40 and PVRL2 with plasma amyloid-β and Alzheimer's disease among Chinese older adults: a population-based study

Whole-genome sequencing reveals the impact of lipid pathway and APOE genotype on brain amyloidosis

Amyloid-PET imaging tracks the accumulation of amyloid beta (Aβ) deposits in the brain. Amyloid plaques accumulation may begin 10 to 20 years before the individual experiences clinical symptoms associated with Alzheimer's diseases (ad). Recent large-scale genome-wide association studies reported common risk factors associated with brain amyloidosis, suggesting that this endophenotype is driven by genetic variants. However, these loci pinpoint to large genomic regions and the functional variants remain to be identified. To identify new risk factors associated with brain amyloid deposition, we performed whole-genome sequencing on a large cohort of European descent individuals with amyloid PET imaging data (n = 1,888). Gene-based analysis for coding variants was performed using SKAT-O for amyloid PET as a quantitative endophenotype that identified genome-wide significant association for APOE (P = 2.45 × 10-10), and 26 new candidate genes with suggestive significance association (P < 5. 0 × 10-03) including SCN7A (P = 7.31 × 10-05), SH3GL1 (P = 7.56 × 10-04), and MFSD12 (P = 8.51 × 10-04). Enrichment analysis highlighted the lipid binding pathways as associated with Aβ deposition in brain driven by PITPNM3 (P = 4.27 × 10-03), APOE (P = 2.45 × 10-10), AP2A2 (P = 1.06 × 10-03), and SH3GL1 (P = 7.56 × 10-04). Overall, our data strongly support a connection between lipid metabolism and the deposition of Aβ in the brain. Our study illuminates promising avenues for therapeutic interventions targeting lipid metabolism to address brain amyloidosis.

The Neurodegenerative Disease Knowledge Portal: Propelling Discovery Through the Sharing of Neurodegenerative Disease Genomic Resources

Although large-scale genetic association studies have proven useful for the delineation of neurodegenerative disease processes, we still lack a full understanding of the pathologic mechanisms of these diseases, resulting in few appropriate treatment options and diagnostic challenges. To mitigate these gaps, the Neurodegenerative Disease Knowledge Portal (NDKP) was created as an open-science initiative with the aim to aggregate, enable analysis, and display all available genomic datasets of neurodegenerative disease, while protecting the integrity and confidentiality of the underlying datasets. The portal contains 218 genomic datasets, including genotyping and sequencing studies, of individuals across 10 different phenotypic groups, including neurologic conditions such as Alzheimer disease, amyotrophic lateral sclerosis, Lewy body dementia, and Parkinson disease. In addition to securely hosting large genomic datasets, the NDKP provides accessible workflows and tools to effectively use the datasets and assist in the facilitation of customized genomic analyses. Here, we summarize the genomic datasets currently included within the portal, the bioinformatics processing of the datasets, and the variety of phenotypes captured. We also present example use cases of the various user interfaces and integrated analytic tools to demonstrate their extensive utility in enabling the extraction of high-quality results at the source, for both genomics experts and those in other disciplines. Overall, the NDKP promotes open science and collaboration, maximizing the potential for discovery from the large-scale datasets researchers and consortia are expending immense resources to produce and resulting in reproducible conclusions to improve diagnostic and therapeutic care for patients with neurodegenerative disease.

Multi-Ancestry Transcriptome-Wide Association Studies of Cognitive Function, White Matter Hyperintensity, and Alzheimer's Disease

Genetic variants increase the risk of neurocognitive disorders in later life, including vascular dementia (VaD) and Alzheimer's disease (AD), but the precise relationships between genetic risk factors and underlying disease etiologies are not well understood. Transcriptome-wide association studies (TWASs) can be leveraged to better characterize the genes and biological pathways underlying genetic influences on disease. To date, almost all existing TWASs on VaD and AD have been conducted using expression studies from individuals of a single genetic ancestry, primarily European. Using the joint likelihood-based inference framework in Multi-ancEstry TRanscriptOme-wide analysis (METRO), we leveraged gene expression data from European ancestry (EA) and African ancestry (AA) samples to identify genes associated with general cognitive function, white matter hyperintensity (WMH), and AD. Regions were fine-mapped using Fine-mapping Of CaUsal gene Sets (FOCUS). We identified 266, 23, 69, and 2 genes associated with general cognitive function, WMH, AD (using EA GWAS summary statistics), and AD (using AA GWAS), respectively (Bonferroni-corrected alpha = p < 2.9 × 10-6), some of which had been previously identified. Enrichment analysis showed that many of the identified genes were in pathways related to innate immunity, vascular dysfunction, and neuroinflammation. Further, the downregulation of ICA1L was associated with a higher WMH and with AD, indicating its potential contribution to overlapping AD and VaD neuropathology. To our knowledge, our study is the first TWAS on cognitive function and neurocognitive disorders that used expression mapping studies for multiple ancestries. This work may expand the benefits of TWASs beyond a single ancestry group and help to identify gene targets for pharmaceuticals or preventative treatments for dementia.

The Neurodegenerative Disease Knowledge Portal: Propelling Discovery Through the Sharing of Neurodegenerative Disease Genomic Resources

Although large-scale genetic association studies have proven useful for the delineation of neurodegenerative disease processes, we still lack a full understanding of the pathological mechanisms of these diseases, resulting in few appropriate treatment options and diagnostic challenges. To mitigate these gaps, the Neurodegenerative Disease Knowledge Portal (NDKP) was created as an open-science initiative with the aim to aggregate, enable analysis, and display all available genomic datasets of neurodegenerative disease, while protecting the integrity and confidentiality of the underlying datasets. The portal contains 218 genomic datasets, including genotyping and sequencing studies, of individuals across ten different phenotypic groups, including neurological conditions such as Alzheimer's disease, amyotrophic lateral sclerosis, Lewy body dementia, and Parkinson's disease. In addition to securely hosting large genomic datasets, the NDKP provides accessible workflows and tools to effectively utilize the datasets and assist in the facilitation of customized genomic analyses. Here, we summarize the genomic datasets currently included within the portal, the bioinformatics processing of the datasets, and the variety of phenotypes captured. We also present example use-cases of the various user interfaces and integrated analytic tools to demonstrate their extensive utility in enabling the extraction of high-quality results at the source, for both genomics experts and those in other disciplines. Overall, the NDKP promotes open-science and collaboration, maximizing the potential for discovery from the large-scale datasets researchers and consortia are expending immense resources to produce and resulting in reproducible conclusions to improve diagnostic and therapeutic care for neurodegenerative disease patients.

Association of dementia with impaired kidney function and plasma biomarkers: A population-based study

BACKGROUND AND PURPOSE

Emerging evidence has linked impaired kidney function with dementia in older adults, but the neuropathological pathways underlying their association remain poorly understood. We sought to examine the relationships of kidney function with dementia and plasma biomarkers in a Chinese rural population.

METHODS

This population-based study used data from the baseline examination of the Multimodal Interventions to Delay Dementia and Disability in rural China (MIND-China) cohort (March-September 2018; n = 5715). Kidney function was assessed using estimated glomerular filtration rate (eGFR) based on serum creatinine level. Dementia, Alzheimer's disease (AD) and vascular dementia (VaD) were diagnosed according to the international criteria. Plasma biomarkers were measured using the SIMOA platform in a subsample (n = 1446). Data were analyzed using logistic, general linear, and mediation models.

RESULTS

Of the 5715 participants, 306 were diagnosed with dementia, including 195 with AD and 100 with VaD. Impaired kidney function (eGFR <60 vs. ≥90 mL/min/1.73 m2) was associated with multivariable-adjusted odds ratios of 2.24 (95% confidence interval [CI] 1.44-3.46) for all-cause dementia, 1.85 (1.07-3.18) for AD, and 2.49 (1.16-5.22) for VaD. In the biomarker subsample, impaired kidney function was significantly associated with higher plasma amyloid-β (Aβ)40 (β-coefficient = 54.36, 95% CI 43.34-65.39), Aβ42 (β-coefficient = 3.14, 95% CI 2.42-3.86), neurofilament light chain (β-coefficient = 10.62, 95% CI 5.62-15.62), and total tau (β-coefficient = 0.68, 95% CI 0.44-0.91), and a lower Aβ42/Aβ40 ratio (β-coefficient = -4.11, 95% CI -8.08 to -0.14). The mediation analysis showed that plasma total tau significantly mediated 21.76% of the association between impaired kidney function and AD (p < 0.05).

CONCLUSION

Impaired kidney function is associated with dementia and plasma biomarkers among rural-dwelling older Chinese adults, and the association with AD is partly mediated by plasma biomarkers for neurodegeneration.

Translocase of Outer Mitochondrial Membrane 40, as a Promising Biomarker for the Diagnosis of Polycystic Ovary Syndrome and Pan-Cancer

Polycystic ovary syndrome (PCOS) is a metabolic disease that affects the reproductive system, and its pathogenesis remains unresolved. Through the application of bioinformatics and molecular biology techniques, this study has identified a significant association between translocase of outer mitochondrial membrane 40 (TOMM40) and both PCOS and pan-cancers. The selection of PCOS biomarkers included TOMM40, which we found to be significantly decreased in the PCOS group both in vitro and in vivo, using molecular biology methods such as Western Blot as well as immunohistochemistry. Over-expression TOMM40 can rescue the effect on apoptosis rate and proliferation suppression induced by DHEA in KGN cells. TOMM40 as a biomarker for the diagnosis of PCOS. The pan-cancer analysis revealed an association between elevated TOMM40 expression in Uterine Corpus Endometrial Carcinoma and an unfavorable prognosis, while increased TOMM40 expression in six tumor types was linked to a favorable prognosis. Therefore, TOMM40 can be regarded as a promising biomarker for diagnosing both PCOS and pan-cancer.

Mapping grey matter and cortical thickness alterations associated with subjective cognitive decline and mild cognitive impairment among rural-dwelling older adults in China: A population-based study

BACKGROUND

The structural brain alterations for subjective cognitive decline (SCD) and mild cognitive impairment (MCI) are poorly defined. We sought to characterize grey matter volume (GMV) and cortical thickness associated with SCD and MCI among rural-dwelling older adults in China.

METHODS

This population-based cross-sectional study included 1072 dementia-free participants from the brain MRI sub-study of MIND-China (2018-2020). We defined MCI following the Petersen's criteria, and SCD as the self-rated Ascertain Dementia 8-item Questionnaire score ≥ 2. Data were analyzed using voxel-based morphometry (VBM), surface-based morphometry analysis (SBM), and logistic regression models.

RESULTS

SCD was defined in 243 persons and MCI in 246 individuals. The VBM analysis showed that MCI (vs. normal cognition) was significantly associated with reduced GMV in brain regions such as the bilateral parahippocampus, bilateral hippocampus, and bilateral fusiform (P < 0.05), but SCD exhibited no significant differences with normal cognition in GMV (P > 0.05). The ROI-wise SBM analysis revealed that SCD was significantly associated with cortical thinning in the right paracentral sulcus, left caudal middle frontal gyrus, and left entorhinal cortex (P < 0.05) and that MCI was significantly associated with cortical thinning in the left temporal lobe, left frontal lobe, bilateral parietal lobe and bilateral fusiform (P < 0.05).

CONCLUSIONS

The brain regions with reduced GMV or cortical thickness in older adults gradually expand from normal cognition through SCD to MCI, suggesting that characterizing structural brain alterations may help define the cognitive spectrum at the pre-dementia phase. These findings have potential implications for understanding the neuropathological process of cognitive deterioration in aging.

Synergistic associations of CD33 variants and hypertension with brain and cognitive aging among dementia-free older adults: A population-based study

INTRODUCTION

CD33 rs3865444 and hypertension (HTN) are related to cognitive impairment, individually. However, little is known about their combined effects on cognitive function in older adults.

METHODS

This population-based study included 4368 dementia-free participants (age ≥65 years) in the Multimodal Interventions to Delay Dementia and Disability in Rural China (MIND-China), with data available in 1044 persons for gray matter volume and 85 persons for cerebral blood flow (CBF). We used general linear regression and mediation models to examine the associations of rs3865444 and HTN with cognition, brain atrophy, and CBF.

RESULTS

Among rs3865444 CC carriers, HTN and late-life HTN were significantly associated with impaired cognition. Midlife and late-life HTN were correlated with brain atrophy. CD33 rs3865444 CC moderated the mediation effect of gray matter volume on the association between HTN and global cognition. HTN was correlated with low CBF in rs3865444 CC carriers.

DISCUSSION

There are synergistic associations of CD33 rs3865444 and HTN with brain and cognitive aging in dementia-free older adults.

The lifestyle for brain health index, the cluster of differentiation 33 (CD33) gene, and cognitive function among rural Chinese older adults: A population-based study

BACKGROUND

We sought to examine the associations of the Lifestyle for Brain Health (LIBRA) index with cognitive function among rural Chinese older adults and to explore the potential role of cluster of differentiation 33 gene (CD33) in the associations.

METHODS

This population-based cross-sectional study included 4914 dementia-free participants (age ≥60 years; 56.43 % women) in the 2018 baseline examination of MIND-China. The LIBRA index was generated from 11 factors. We used a neuropsychological test battery to assess episodic memory, verbal fluency, attention, executive function, and global cognition. The CD33(rs3865444) polymorphism was detected using multiple-polymerase chain reaction amplification. Data were analyzed using the general linear regression models.

RESULTS

A higher LIBRA index was associated with multivariable-adjusted β-coefficient (95 %CI) of -0.011(-0.020- -0.001) for global cognitive z-score, -0.020(-0.033- -0.006) for episodic memory, and -0.016(-0.029- -0.004) for verbal fluency. The CD33(rs3865444) was associated with a lower global cognitive z-score in the additive (CA vs. CC: β-coefficient=0.042; 95 %CI=0.008-0.077), the dominant (CA+AA vs. CC: 0.040; 0.007-0.073), and the over-dominant (CA vs. CC+AA: 0.043; 0.009-0.077) models. Similar results were obtained for verbal fluency and attention. The CD33 gene showed statistical interactions with LIBRA index on cognitive function (Pinteraction<0.05) such that a higher LIBRA index was significantly associated with lower z-scores of global cognition and attention only among CD33 CC carriers (P < 0.05).

CONCLUSIONS

This population-based study reveals for the first time that a higher LIBRA index is associated with worse cognitive performance in rural Chinese older adults and that CD33 gene could modify the association.

Association of polygenic risk scores with Alzheimer's disease and plasma biomarkers among Chinese older adults: A community-based study

INTRODUCTION

We examined the associations of polygenic risk score (PRS) with Alzheimer's disease (AD) and plasma biomarkers in the Chinese population.

METHODS

This population-based study used baseline data from MIND-China (2018; n = 4873) and follow-up data from dementia-free individuals (2014-2018; n = 2117). We measured AD-related plasma biomarkers in a subsample (n = 1256). Data were analyzed using logistic and Cox regression models.

RESULTS

We developed PRS with (PRSAPOE) and without (PRSnon- APOE) apolipoprotein E (APOE) gene. In the longitudinal analysis, PRSAPOE was associated with a multivariable-adjusted hazards ratio of 1.91 (95% CI = 1.13-3.23) for AD. PRSAPOE in combination with demographics yielded discriminative (area under the curve [AUC]) and predictive(C-statistic) accuracy of 0.80 (95% confidence interval [CI] = 0.77-0.84) and 0.80 (0.77-0.82), respectively. PRSnon- APOE showed an association with AD risk similar to PRSAPOE. PRSAPOE, but not PRSnon- APOE, was associated with reduced plasma Aβ42/Aβ40 ratio and increased Neurofilament light chain (NfL) (p < 0.05).

DISCUSSION

The PRS with and without APOE gene, in combination with demographics, shows good discriminative and predictive ability for AD. The AD-related pathologies underlie AD risk associated with PRSAPOE.

HIGHLIGHTS

The PRSAPOE and PRSnon- APOE were associated with AD risk in the Chinese population. The PRSAPOE and PRSnon- APOE, in combination with demographics, showed good discriminative and predictive ability for AD. The AD-related pathologies underlie the AD risk associated with PRSAPOE but not PRSnon- APOE.

Association of Triglyceride-Glucose Index With Cognitive Function and Brain Atrophy: A Population-Based Study

OBJECTIVE

To investigate the associations of triglyceride-glucose (TyG) index, a reliable surrogate marker for insulin resistance, with the function of various cognitive domains and brain structures among older adults.

DESIGN

A population-based cross-sectional study.

SETTING

Older adults living in the rural communities in China.

PARTICIPANTS

About 4,541 rural-dwelling dementia-free participants (age ≥65 years; 56.37% women) undertook examinations in March-September 2018 for MIND-China.

MEASUREMENTS

TyG index was calculated as ln[fasting triglyceride (mg/dL) × fasting glucose (mg/dL)/2]. A neuropsychological test battery was used to assess memory, attention, verbal fluency, and executive function. Volumetric brain measures were assessed on magnetic resonance imaging (MRI) in a subsample (n = 1,019). Data were analyzed with restricted cubic spline and multivariable general linear models.

RESULTS

An inverted J-shaped association was observed between TyG index and z-scores of multiple cognitive domains, such that among individuals with TyG index ≥8.57 (median), a higher TyG index was significantly associated with lower z-scores of memory, attention, verbal fluency, executive function, and global cognition (all p < 0.05); among people with TyG index <8.57, a higher TyG index was significantly associated with a higher executive function z-score (p < 0.05), but not with any of the other examined cognitive domains. In the MRI subsample, a higher TyG index was significantly associated with lower volumes of total brain tissue, gray matter, and white matter as well as greater cerebrospinal fluid volume (p < 0.05), but not with white matter hyperintensity volume.

CONCLUSIONS

Insulin resistance, as indicated by a high TyG index, was associated with poor function in multiple cognitive domains and global brain atrophy.

Differential Associations of 6 Adiposity Indices With Dementia in Older Adults: The MIND-China Study

OBJECTIVES

The cross-sectional association between late-life obesity and dementia is often explained by the obesity paradox. We assessed the potential differential associations of various adiposity indices with dementia and subtypes of dementia in rural Chinese older adults.

DESIGN

A population-based cross-sectional study.

SETTING AND PARTICIPANTS

A total of 5277 participants (age ≥60 years; 57.23% female) who were living in rural communities and were examined in March-September 2018 for MIND-China.

METHODS

We used weight, height, and waist circumference (WC) to calculate 6 adiposity indices: body mass index (BMI), waist-to-height ratio (WHtR), weight-adjusted-waist index (WWI), A Body Shape Index (ABSI), body roundness index (BRI), and Conicity Index (ConI). Dementia, Alzheimer's disease (AD), and vascular dementia (VaD) were clinically diagnosed following the international criteria. Data were analyzed with logistic regression models.

RESULTS

Of the 5277 participants, 303 were diagnosed with dementia, including 193 with AD and 99 with VaD. The multivariable-adjusted odds ratio (95% CI) of dementia associated with the highest (vs lowest) quintile of adiposity index was 2.32 (1.40-3.85) for WWI, 1.56 (1.03-2.36) for ABSI, and 1.40 (0.92-2.11) for ConI. Similarly, higher levels of these 3 adiposity indices were significantly associated with an increased likelihood of AD, whereas a higher BMI was associated with a decreased likelihood of AD. None of the 6 examined adiposity indices was significantly associated with VaD when adjusting for multiple confounders.

CONCLUSIONS AND IMPLICATIONS

The adiposity index WWI is linearly associated with the likelihood of dementia and AD. An increased WWI may be a clinical marker for the dementia syndrome and Alzheimer's dementia.

The Association of Selected GWAS Reported AD Risk Loci with CSF Biomarker Levels and Cognitive Decline in Slovenian Patients

Alzheimer's disease (AD) is the most common neurodegenerative disease, with a complex genetic background. Apart from rare, familial cases, a combination of multiple risk loci contributes to the susceptibility of the disease. Genome-wide association studies (GWAS) have identified numerous AD risk loci. Changes in cerebrospinal fluid (CSF) biomarkers and imaging techniques can detect AD-related brain changes before the onset of clinical symptoms, even in the presence of preclinical mild cognitive impairment. In this study, we aimed to assess the associations between SNPs in well-established GWAS AD risk loci and CSF biomarker levels or cognitive test results in Slovenian patients with cognitive decline. The study included 82 AD patients, 28 MCI patients with pathological CSF biomarker levels and 35 MCI patients with normal CSF biomarker levels. Carriers of at least one polymorphic TOMM40 rs157581 C allele had lower Aβ42 (p = 0.033) and higher total tau (p = 0.032) and p-tau181 levels (p = 0.034). Carriers of at least one polymorphic T allele in SORCS1 rs1358030 had lower total tau (p = 0.019), while polymorphic SORCS1 rs1416406 allele was associated with lower total tau (p = 0.013) and p-tau181 (p = 0.036). In addition, carriers of at least one polymorphic T allele in BCHE rs1803274 had lower cognitive test scores (p = 0.029). The study findings may contribute to the identification of genetic markers associated with AD and MCI and provide insights into early disease diagnostics.

Association of Lifelong Cognitive Reserve with Dementia and Mild Cognitive Impairment among Older Adults with Limited Formal Education: A Population-Based Cohort Study

INTRODUCTION

Early-life educational attainment contributes to cognitive reserve (CR). We investigated the associations of lifelong CR with dementia and mild cognitive impairment (MCI) among older people with limited formal education.

METHODS

This population-based cohort study included 2,127 dementia-free participants (≥60 years; 59.4% women; 81.5% with no or elementary school) who were examined at baseline (August-December 2014) and follow-up (March-September 2018). Lifelong CR score at baseline was generated from six lifespan intellectual factors. Dementia, MCI, and their subtypes were defined according to the international criteria. Data were analyzed using Cox proportional-hazards models.

RESULTS

During the total of 8,330.6 person-years of follow-up, 101 persons were diagnosed with dementia, including 74 with Alzheimer's disease (AD) and 26 with vascular dementia (VaD). The high (vs. low) tertile of lifelong CR score was associated with multivariable-adjusted hazards ratios (95% confidence interval) of 0.28 (0.14-0.55) for dementia and 0.18 (0.07-0.48) for AD. The association between higher CR and reduced AD risk was significant in people aged 60-74 but not in those aged ≥75 years (p for interaction = 0.011). Similarly, among MCI-free people at baseline (n = 1,635), the high (vs. low) tertile of lifelong CR score was associated with multivariable-adjusted hazard ratios of 0.51 (0.38-0.69) for MCI and 0.46 (0.33-0.64) for amnestic MCI. Lifelong CR was not related to VaD or non-amnestic MCI.

DISCUSSION

High lifelong CR is associated with reduced risks of dementia and MCI, especially AD and amnestic MCI. It highlights the importance of lifelong CR in maintaining late-life cognitive health even among people with no or limited education.

Objectively-measured movement behaviors, systemic low-grade inflammation, and plasma neurofilament light chain in older adults: a population-based study

BACKGROUND

Evidence has linked self-reported sedentary behavior (SB) and physical activity (PA) with cognitive impairment; however, the underlying mechanisms are poorly understood. We examined the associations of the accelerometer-measured movement behaviors with plasma neurofilament light chain (NfL) among older adults and the role of systemic low-grade inflammation in the associations.

RESULTS

This population-based study included 1,029 dementia-free older adults (age ≥ 60 years, range 60-88 years; 59.48% women) who undertook the ActiGraph substudy (March 2018-December 2020) in MIND-China. There were nonlinear relationships of daily SB and PA time with plasma NfL concentration, such that more daily SB time or less time spent in daily light-intensity physical activity (LPA) and moderate-to-vigorous-intensity physical activity (MVPA) was significantly associated with increased plasma NfL only when SB time ≥ 8.00 h/day or LPA time < 5.00 h/day or MVPA time < 2.00 h/day. Furthermore, more daily SB time or less daily LPA and MVPA time was significantly associated with higher serum low-grade inflammation score, a composite measure generated from serum IL-6, IL-8, TNF-α, and ICAM-1 (P < 0.05). Finally, low-grade inflammation score accounted for 14.5% to 17.8% of the associations between movement behaviors and plasma NfL.

CONCLUSIONS

More daily SB and less PA time are associated with neurodegeneration and systemic low-grade inflammation in older adults. The association of movement behaviors with neurodegeneration is partially mediated by low-grade inflammation.

Prevalence and Progression of Subjective Cognitive Decline Among Rural Chinese Older Adults: A Population-Based Study

BACKGROUND

Few community-based studies have examined occurrence and progression of subjective cognitive decline (SCD).

OBJECTIVE

To investigate prevalence and progression of SCD among rural-dwelling Chinese elderly people.

METHODS

This cohort study included 2,488 cognitively unimpaired adults (age≥65 years) who were examined at baseline (2014-2015) and followed in 2018. Demographic, epidemiological, clinical, and neuropsychological data were collected via in-person interviews and clinical examinations following a structured questionnaire. At baseline, SCD was assessed using the self-rated Ascertain Dementia 8-item Questionnaire. At follow-up, Alzheimer's disease (AD) and vascular dementia (VaD) were clinically diagnosed following the international criteria. Data were analyzed using logistic regression models.

RESULTS

The prevalence of SCD was 40.07%. SCD at baseline was associated with the multivariable-adjusted odds ratio (OR) of 1.51 (95% confidence interval 1.10-2.07) for incident cognitive impairment, no dementia (CIND) and 3.11 (1.64-5.93) for incident AD. Among people with SCD at baseline, the multivariable-adjusted OR of incident CIND was 0.55(0.32-0.96) for hyperlipidemia; the multivariable-adjusted OR of incident AD was 1.21 (1.14-1.30) for older age, 0.32 (0.12-0.88) for high education, 2.60 (1.11-6.08) for carrying APOEɛ4 allele, and 0.34 (0.13-0.86) for high social support, whereas the multivariable-adjusted OR of incident VaD was 6.30 (1.71-23.18) for obesity.

CONCLUSION

SCD affects over 40% of rural-dwelling cognitively unimpaired older adults in China. SCD is associated with accelerated progression to CIND and AD. Older age, lack of school education, APOEɛ4 allele, and low social support are associated with an increased risk of progression from SCD to AD, whereas obesity is related to accelerated progression to VaD.

Associations of WWC1 variants with Alzheimer's disease and vascular dementia among rural older adults in China: A population-based study

We sought to examine the associations of common WWC1 variants with Alzheimer's disease (AD) and vascular dementia (VaD) among rural-dwelling older adults in China. This population-based study used data from the baseline assessments (March -September 2018) of MIND-China. AD and VaD were diagnosed following the international criteria. Of the 5455 participants (age≥60 years, 57.27% women), 182 were diagnosed with AD and 88 with VaD. Logistic regression analysis suggested that WWC1 rs17070145 C allele (vs. T) was associated with multivariable-adjusted odds ratio of 1.23 (95% confidence interval 0.96-1.58) for AD, and that CC genotype (vs. TT) was associated with multivariable-adjusted odds ratio of 2.19(1.10-4.39) for VaD, but the association with VaD became non-significant when further adjusting for stroke history. Furthermore, exonic SNPs rs3822660 and rs3822659 were in strong linkage disequilibrium (LD) with rs17070145 (D' = 0.88). These results suggest that the strong LD between rs17070145 and 2 exonic SNPs may explain the association of WWC1 rs17070145 C allele with AD and that stroke may partly explain the association of WWC1 rs17070145 CC genotype with VaD.

Cardiovascular health profiles, systemic inflammation, and physical function in older adults: A population-based study

We examined the association of modifiable cardiovascular health (CVH) metrics with physical function among rural older adults in China and the potential role of inflammatory mechanisms in the association. This study included 3733 stroke- and dementia-free participants (age ≥65 years; 56.9% women) in the baseline survey of a multimodal intervention study in rural China. From March-September 2018, data were collected via face-to-face interviews, clinical assessments, and laboratory tests. The Short Performance Physical Battery (SPPB) test was performed to assess physical function. We defined six modifiable CVH metrics according to the modified American Heart Association's recommendations. Serum interleukin (IL)-6 was measured in a subsample (n = 1156). Data were analyzed with multiple general linear and logistic regression models and structural equation modeling. Poor physical function (SPPB score ≤9) was defined in 1443 participants. Ideal CVH (vs. poor CVH) was associated with multivariable-adjusted odds ratio of 0.60 (95%CI 0.48-0.75) for poor physical function. Ideal CVH was significantly associated with higher scores on balance, chair stand, and walking speed tests (all p < 0.05). Moreover, ideal CVH profile was associated with lower serum IL-6 (multivariable-adjusted β=-0.04; 95% CI -0.06, -0.01). Mediation analysis revealed that serum IL-6 accounted for 14% of the association of CVH with total SPPB score and 10% of the association with walking speed score (p < 0.05). This study suggests that an ideal CVH profile is associated with better physical function among stroke- and dementia-free older adults, partly via inflammatory mechanisms. The preventive implications of these findings warrant further investigation in cohort studies.

Ventricular Electrocardiographic Signatures Associated with Dementia and Plasma Alzheimer's Disease Biomarkers in Older Adults: A Population-Based Study

BACKGROUND

Evidence has emerged that altered ventricular electrocardiogram profiles are associated with dementia, but the neuropathological mechanisms underlying their associations are poorly understood.

OBJECTIVE

To investigate the interrelationships of ventricular electrocardiogram profiles with dementia and plasma Alzheimer's disease (AD) biomarkers among older adults.

METHODS

This population-based cross-sectional study included 5,153 participants (age ≥65 years; 57.3% women) living in rural communities in China; of these, 1,281 had data on plasma amyloid-β (Aβ)40, Aβ42, total-tau, and neurofilament light chain (NfL) protein. The QT, QTc, JT, JTc, QRS intervals, and QRS axis were derived from the 10-second electrocardiogram recording. The DSM-IV criteria were followed for clinical diagnosis of dementia, the NIA-AA criteria for AD, and the NINDS-AIREN criteria for vascular dementia (VaD). Data were analyzed using general linear models, multinomial logistic models, and restricted cubic splines.

RESULTS

Of the 5,153 participants, 299 (5.8%) were diagnosed with dementia, including 194 with AD and 94 with VaD. Prolonged QT, QTc, JT, and JTc intervals were significantly associated with all-cause dementia, AD, and VaD (p < 0.05). Left QRS axis deviation was significantly associated with all-cause dementia and VaD (p < 0.01). In the subsample of plasma biomarkers (n = 1,281), prolonged QT, JT, and JTc intervals were significantly associated with a lower Aβ42/Aβ40 ratio and higher plasma NfL concentrations (p < 0.05).

CONCLUSION

Alterations in ventricular repolarization and depolarization are independently associated with all-cause dementia, AD, VaD, and AD plasma biomarkers in older adults (age ≥65 years). Ventricular electrocardiogram parameters may be valuable clinical markers for dementia and the underlying AD pathologies and neurodegeneration.

Accelerometer-Measured Sedentary Behavior Patterns, Brain Structure, and Cognitive Function in Dementia-Free Older Adults: A Population-Based Study

BACKGROUND

Sedentary behavior is associated with cognitive impairment, but the neuropathological mechanisms underlying their associations are poorly understood.

OBJECTIVE

To investigate the associations of accelerometer-measured sedentary behavior patterns with brain structure and cognition, and further to explore the potential mechanisms.

METHODS

This community-based study included 2,019 older adults (age≥60 years, 59% women) without dementia derived from participants in the baseline examination of MIND-China (2018-2020). We assessed sedentary parameters using an accelerometer and cognitive function using a neuropsychological test battery. Structural brain markers were assessed on the structural brain MRI scans in a subsample (n = 1,009). Data were analyzed using the general linear, isotemporal substitution, and mediation models.

RESULTS

In the total sample (n = 2,019), adjusting for multiple covariates and moderate-to-vigorous-intensity physical activity, longer mean sedentary bout duration was linearly related with lower z-scores of global cognition, verbal fluency, and memory (ptrend < 0.05), whereas greater total sedentary time was linearly associated with lower z-scores of global cognition, verbal fluency, and memory only among individuals with long sedentary time (>10 h/day) (ptrend < 0.05); Breaking up sedentary time with same amount of light-intensity physical activity was significantly associated with higher verbal fluency and memory z-scores (p < 0.05). In the MRI subsample (n = 1,009), separately entering structural brain MRI markers into the mediation models substantially attenuated the associations of mean sedentary bout duration with global cognition, verbal fluency, and memory z-scores.

CONCLUSION

Prolonged uninterrupted sedentary time is associated with poor global cognition, memory, and verbal fluency among rural older adults, and structural brain markers could partially mediate the association.

Thalamic gray matter volume mediates the association between KIBRA polymorphism and olfactory function among older adults: a population-based study

The kidney and brain expressed protein (KIBRA) rs17070145 polymorphism is associated with both structure and activation of the olfactory cortex. However, no studies have thus far examined whether KIBRA can be linked with olfactory function and whether brain structure plays any role in the association. We addressed these questions in a population-based cross-sectional study among rural-dwelling older adults. This study included 1087 participants derived from the Multidomain Interventions to Delay Dementia and Disability in Rural China, who underwent the brain MRI scans in August 2018 to October 2020; of these, 1016 took the 16-item Sniffin' Sticks identification test and 634 (62.40%) were defined with olfactory impairment (OI). Data were analyzed using the voxel-based morphometry analysis and general linear, logistic, and structural equation models. The KIBRA rs17070145 C-allele (CC or CT vs. TT genotype) was significantly associated with greater gray matter volume (GMV) mainly in the bilateral orbitofrontal cortex and left thalamus (P < 0.05) and with the multi-adjusted odds ratio of 0.73 (95% confidence interval 0.56-0.95) for OI. The left thalamic GMV could mediate 8.08% of the KIBRA-olfaction association (P < 0.05). These data suggest that the KIBRA rs17070145 C-allele is associated with a reduced likelihood of OI among older adults, partly mediated through left thalamic GMV.