Multi-omics and pathway analyses of genome-wide associations implicate regulation and immunity in verbal declarative memory performance

BACKGROUND

Uncovering the functional relevance underlying verbal declarative memory (VDM) genome-wide association study (GWAS) results may facilitate the development of interventions to reduce age-related memory decline and dementia.

METHODS

We performed multi-omics and pathway enrichment analyses of paragraph (PAR-dr) and word list (WL-dr) delayed recall GWAS from 29,076 older non-demented individuals of European descent. We assessed the relationship between single-variant associations and expression quantitative trait loci (eQTLs) in 44 tissues and methylation quantitative trait loci (meQTLs) in the hippocampus. We determined the relationship between gene associations and transcript levels in 53 tissues, annotation as immune genes, and regulation by transcription factors (TFs) and microRNAs. To identify significant pathways, gene set enrichment was tested in each cohort and meta-analyzed across cohorts. Analyses of differential expression in brain tissues were conducted for pathway component genes.

RESULTS

The single-variant associations of VDM showed significant linkage disequilibrium (LD) with eQTLs across all tissues and meQTLs within the hippocampus. Stronger WL-dr gene associations correlated with reduced expression in four brain tissues, including the hippocampus. More robust PAR-dr and/or WL-dr gene associations were intricately linked with immunity and were influenced by 31 TFs and 2 microRNAs. Six pathways, including type I diabetes, exhibited significant associations with both PAR-dr and WL-dr. These pathways included fifteen MHC genes intricately linked to VDM performance, showing diverse expression patterns based on cognitive status in brain tissues.

CONCLUSIONS

VDM genetic associations influence expression regulation via eQTLs and meQTLs. The involvement of TFs, microRNAs, MHC genes, and immune-related pathways contributes to VDM performance in older individuals.

Serum proteomics reveals APOE dependent and independent protein signatures in Alzheimer's disease

The current demand for early intervention, prevention, and treatment of late onset Alzheimer's disease (LOAD) warrants deeper understanding of the underlying molecular processes which could contribute to biomarker and drug target discovery. Utilizing high-throughput proteomic measurements in serum from a prospective population-based cohort of older adults (n = 5,294), we identified 303 unique proteins associated with incident LOAD (median follow-up 12.8 years). Over 40% of these proteins were associated with LOAD independently of APOE-ε4 carrier status. These proteins were implicated in neuronal processes and overlapped with protein signatures of LOAD in brain and cerebrospinal fluid. We found 17 proteins which LOAD-association was strongly dependent on APOE-ε4 carrier status. Most of them showed consistent associations with LOAD in cerebrospinal fluid and a third had brain-specific gene expression. Remarkably, four proteins in this group (TBCA, ARL2, S100A13 and IRF6) were downregulated by APOE-ε4 yet upregulated as a consequence of LOAD as determined in a bi-directional Mendelian randomization analysis, reflecting a potential response to the disease onset. Accordingly, the direct association of these proteins to LOAD was reversed upon APOE-ε4 genotype adjustment, a finding which we replicate in an external cohort (n = 719). Our findings provide an insight into the dysregulated pathways that may lead to the development and early detection of LOAD, including those both independent and dependent on APOE-ε4. Importantly, many of the LOAD-associated proteins we find in the circulation have been found to be expressed - and have a direct link with AD - in brain tissue. Thus, the proteins identified here, and their upstream modulating pathways, provide a new source of circulating biomarker and therapeutic target candidates for LOAD.

A proteomic analysis of atrial fibrillation in a prospective longitudinal cohort (AGES-Reykjavik study)

AIMS

Atrial fibrillation (AF) is associated with high risk of comorbidities and mortality. Our aim was to examine causal and predictive relationships between 4137 serum proteins and incident AF in the prospective population-based Age, Gene/Environment Susceptibility-Reykjavik (AGES-Reykjavik) study.

METHODS AND RESULTS

The study included 4765 participants, of whom 1172 developed AF. Cox proportional hazards regression models were fitted for 4137 baseline protein measurements adjusting for known risk factors. Protein associations were tested for replication in the Cardiovascular Health Study (CHS). Causal relationships were examined in a bidirectional, two-sample Mendelian randomization analysis. The time-dependent area under the receiver operating characteristic curve (AUC)-statistic was examined as protein levels and an AF-polygenic risk score (PRS) were added to clinical risk models. The proteomic signature of incident AF consisted of 76 proteins, of which 63 (83%) were novel and 29 (38%) were replicated in CHS. The signature included both N-terminal prohormone of brain natriuretic peptide (NT-proBNP)-dependent (e.g. CHST15, ATP1B1, and SVEP1) and independent components (e.g. ASPN, AKR1B, and LAMA1/LAMB1/LAMC1). Nine causal candidates were identified (TAGLN, WARS, CHST15, CHMP3, COL15A1, DUSP13, MANBA, QSOX2, and SRL). The reverse causal analysis suggested that most AF-associated proteins were affected by the genetic liability to AF. N-terminal prohormone of brain natriuretic peptide improved the prediction of incident AF events close to baseline with further improvements gained by the AF-PRS at all time points.

CONCLUSION

The AF proteomic signature includes biologically relevant proteins, some of which may be causal. It mainly reflects an NT-proBNP-dependent consequence of the genetic liability to AF. N-terminal prohormone of brain natriuretic peptide is a promising marker for incident AF in the short term, but risk assessment incorporating a PRS may improve long-term risk assessment.

Milk intake and hip fracture incidence in community-dwelling old Icelandic adults

Milk and milk products have been known as important for bone health. Can ingestion of milk and milk products lower hip fracture risk for older adults? In this study, older Icelandic adults who were ingesting higher milk had a lower risk of hip fractures.

INTRODUCTION

This study describes associations between milk intake and hip fracture risk in older Icelanders. The data indicate that no/low milk consumption is related to greater hip fracture risk. Hip fracture can have a severe effect on the life of older adults. Health authorities recommend milk intake for better bone health. However, previous studies addressing this association have been divergent.

METHODS

This prospective study included 4614 subjects (mean age 76 years) recruited between 2002 and 2006 into the Age, Gene/Environment Susceptibility-Reykjavik (AGES-Reykjavik) study. Information on hip fractures occurring between recruitment and end of follow-up in 2012 was extracted from hospital records.

RESULTS

A total of 14% of participants reported milk intake < 0.5 times/day (the lowest category) and 22% of the participants consumed at least milk two times/day (highest category). Milk consumption was positively related to the volumetric bone mineral density at baseline with a sex- and age-adjusted difference of 8.95 ± 2.5 mg/cm3 between the highest compared to lowest milk intake categories (P < 0.001). During the follow-up, 7.4% of participants had a hip fracture, and we observed a decreased risk of incident hip fractures in the highest compared to the lowest milk intake category with a hazard ratio of 0.69 (95% CI: 0.47-0.99) in adjusted model. Further analysis indicated a linear relationship between milk intake and fracture risk (P-value for linear trend < 0.001).

CONCLUSION

Milk intake is associated with a lower risk of incident hip fracture in a linear way in Icelandic community-dwelling older adults.

Genetic insights into resting heart rate and its role in cardiovascular disease

Resting heart rate is associated with cardiovascular diseases and mortality in observational and Mendelian randomization studies. The aims of this study are to extend the number of resting heart rate associated genetic variants and to obtain further insights in resting heart rate biology and its clinical consequences. A genome-wide meta-analysis of 100 studies in up to 835,465 individuals reveals 493 independent genetic variants in 352 loci, including 68 genetic variants outside previously identified resting heart rate associated loci. We prioritize 670 genes and in silico annotations point to their enrichment in cardiomyocytes and provide insights in their ECG signature. Two-sample Mendelian randomization analyses indicate that higher genetically predicted resting heart rate increases risk of dilated cardiomyopathy, but decreases risk of developing atrial fibrillation, ischemic stroke, and cardio-embolic stroke. We do not find evidence for a linear or non-linear genetic association between resting heart rate and all-cause mortality in contrast to our previous Mendelian randomization study. Systematic alteration of key differences between the current and previous Mendelian randomization study indicates that the most likely cause of the discrepancy between these studies arises from false positive findings in previous one-sample MR analyses caused by weak-instrument bias at lower P-value thresholds. The results extend our understanding of resting heart rate biology and give additional insights in its role in cardiovascular disease development.

Deep Learning Based Detection of Enlarged Perivascular Spaces on Brain MRI

Deep learning has been demonstrated effective in many neuroimaging applications. However, in many scenarios, the number of imaging sequences capturing information related to small vessel disease lesions is insufficient to support data-driven techniques. Additionally, cohort-based studies may not always have the optimal or essential imaging sequences for accurate lesion detection. Therefore, it is necessary to determine which imaging sequences are crucial for precise detection. This study introduces a deep learning framework to detect enlarged perivascular spaces (ePVS) and aims to find the optimal combination of MRI sequences for deep learning-based quantification. We implemented an effective lightweight U-Net adapted for ePVS detection and comprehensively investigated different combinations of information from SWI, FLAIR, T1-weighted (T1w), and T2-weighted (T2w) MRI sequences. The experimental results showed that T2w MRI is the most important for accurate ePVS detection, and the incorporation of SWI, FLAIR and T1w MRI in the deep neural network had minor improvements in accuracy and resulted in the highest sensitivity and precision (sensitivity =0.82, precision =0.83). The proposed method achieved comparable accuracy at a minimal time cost compared to manual reading. The proposed automated pipeline enables robust and time-efficient readings of ePVS from MR scans and demonstrates the importance of T2w MRI for ePVS detection and the potential benefits of using multimodal images. Furthermore, the model provides whole-brain maps of ePVS, enabling a better understanding of their clinical correlates compared to the clinical rating methods within only a couple of brain regions.

Abstract P505: Midlife Cognitive Function is Associated With Gut Microbial Species and Metabolic Pathways: Coronary Artery Risk Development in Young Adults (CARDIA) Study

Background: The gut microbiota may play a role in cognitive function and decline. Animal models support mechanisms involving short-chain fatty acid production, amino acid metabolism, and purine metabolism. There is need to replicate these findings in population-based human studies.

Methods: Data were from 570 participants who attended the Yr. 30 follow-up exam (2015-16, ages 48-60 y, 45%:55% Black:White race, 45%:55% M:F sex), provided a fecal sample, and completed a cognitive battery of 6 assessments: Montreal Cognitive Assessment (MoCA), Digit Symbol Substitution Test (DSST), Rey-Auditory Verbal Learning Test (RAVLT), Stroop, and Letter and Category Fluency. A global cognition score was derived from the 6 assessments using principal components analysis. Species and metabolic pathways were assigned to whole-metagenomics sequence data using standard reference databases. Multivariable-adjusted linear regression was used to test associations between distinct microbial features and measures of cognition, controlling for false discovery rate (FDR).

Results: Sequence data mapped to 106 species and 312 metabolic pathways. In multivariable-adjusted regression analysis, adjusted for socio-demographics, health behaviors, and BMI, 5 species and 5 metabolic pathways were significantly associated with measures of cognitive function, FDR < 0.20 (Figure) . These species/pathways are involved in purine and pyrimidine metabolism and short-chain fatty acid production.

Conclusion: Identified pathways play a role in neurodevelopment and in the gut-brain axis of physiologic communications. Our findings suggest long-term relationships between gut microbiota composition and cognitive function.

The rocky road of 55 years of change in the relationship of cardiovascular risk factors to cognition

The mixed evidence that high levels of cardiovascular risk factors (CVRF) are associated with lower cognitive test scores of may be due to confounding of age across studies. We pooled and harmonized individual-level data (30,967 persons, age range 42-96y) from five prospective cohorts to examine the trajectories of betas estimating 1-year-age associations of a cognitive outcome (Digit Symbol Substitution Test; DSST) to five CVRF: systolic and e blood pressure, total cholesterol, fasting glucose and body mass index. Linear and quadratic piecewise regression models were fit to the trajectory patterns of these betas. The trajectories showed with each 1-year age increment, higher CVRF were associated with lower DSST, but associations attenuated toward zero as age increased. In addition, the pattern across age of each CVRF-DSST trajectory ranged from linear to non-liner. Without accounting for participant age in cohort comparisons, conclusions about the potential benefit on cognitive function of modifiable CVRF control will continue to be mixed and lead to delays in developing prevention programs.

SPARE-Tau: A flortaucipir machine-learning derived early predictor of cognitive decline

BACKGROUND

Recently, tau PET tracers have shown strong associations with clinical outcomes in individuals with cognitive impairment and cognitively unremarkable elderly individuals. flortaucipir PET scans to measure tau deposition in multiple brain areas as the disease progresses. This information needs to be summarized to evaluate disease severity and predict disease progression. We, therefore, sought to develop a machine learning-derived index, SPARE-Tau, which successfully detects pathology in the earliest disease stages and accurately predicts progression compared to a priori-based region of interest approaches (ROI).

METHODS

587 participants of the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort had flortaucipir scans, structural MRI scans, and an Aβ biomarker test (CSF or florbetapir PET) performed on the same visit. We derived the SPARE-Tau index in a subset of 367 participants. We evaluated associations with clinical measures for CSF p-tau, SPARE-MRI, and flortaucipir PET indices (SPARE-Tau, meta-temporal, and average Braak ROIs). Bootstrapped multivariate adaptive regression splines linear regression analyzed the association between the biomarkers and baseline ADAS-Cog13 scores. Bootstrapped multivariate linear regression models evaluated associations with clinical diagnosis. Cox-hazards and mixed-effects models investigated clinical progression and longitudinal ADAS-Cog13 changes. The Aβ positive cognitively unremarkable participants, not included in the SPARE-Tau training, served as an independent validation group.

RESULTS

Compared to CSF p-tau, meta-temporal, and averaged Braak tau PET ROIs, SPARE-Tau showed the strongest association with baseline ADAS-cog13 scores and diagnosis. SPARE-Tau also presented the strongest association with clinical progression in cognitively unremarkable participants and longitudinal ADAS-Cog13 changes. Results were confirmed in the Aβ+ cognitively unremarkable hold-out sample participants. CSF p-tau showed the weakest cross-sectional associations and longitudinal prediction.

DISCUSSION

Flortaucipir indices showed the strongest clinical association among the studied biomarkers (flortaucipir, florbetapir, structural MRI, and CSF p-tau) and were predictive in the preclinical disease stages. Among the flortaucipir indices, the machine-learning derived SPARE-Tau index was the most sensitive clinical progression biomarker. The combination of different biomarker modalities better predicted cognitive performance.

Framework for Clinical Trials in Cerebral Small Vessel Disease (FINESSE): A Review

Importance

Cerebral small vessel disease (SVD) causes a quarter of strokes and is the most common pathology underlying vascular cognitive impairment and dementia. An important step to developing new treatments is better trial methodology. Disease mechanisms in SVD differ from other stroke etiologies; therefore, treatments need to be evaluated in cohorts in which SVD has been well characterized. Furthermore, SVD itself can be caused by a number of different pathologies, the most common of which are arteriosclerosis and cerebral amyloid angiopathy. To date, there have been few sufficiently powered high-quality randomized clinical trials in SVD, and inconsistent trial methodology has made interpretation of some findings difficult.

Observations

To address these issues and develop guidelines for optimizing design of clinical trials in SVD, the Framework for Clinical Trials in Cerebral Small Vessel Disease (FINESSE) was created under the auspices of the International Society of Vascular Behavioral and Cognitive Disorders. Experts in relevant aspects of SVD trial methodology were convened, and a structured Delphi consensus process was used to develop recommendations. Areas in which recommendations were developed included optimal choice of study populations, choice of clinical end points, use of brain imaging as a surrogate outcome measure, use of circulating biomarkers for participant selection and as surrogate markers, novel trial designs, and prioritization of therapeutic agents using genetic data via Mendelian randomization.

Conclusions and Relevance

The FINESSE provides recommendations for trial design in SVD for which there are currently few effective treatments. However, new insights into understanding disease pathogenesis, particularly from recent genetic studies, provide novel pathways that could be therapeutically targeted. In addition, whether other currently available cardiovascular interventions are specifically effective in SVD, as opposed to other subtypes of stroke, remains uncertain. FINESSE provides a framework for design of trials examining such therapeutic approaches.

Social network and the risk for developing mild cognitive impairment and dementia among older adults

BACKGROUND

This study aimed to investigate the longitudinal associations between social network (SN) and the risk of lower cognitive function, mild cognitive impairment (MCI), and dementia among cognitively normal individuals 65 years and older.

METHODS

Data from the Age, Gene/Environment Susceptibility (AGES) Reykjavik Study on 2816 participants (aged 65 to 96 years) were used to examine the associations using multiple logistic and linear regression models. SN included questions on frequency of contact with family and friends as well as information on marital status, resulting in a score ranging from 0 (poor social network) to 3 (good social network). Cognitive function outcomes included the speed of processing (SP), executive function (EF) and memory function (MF). MCI and dementia were diagnosed using a detailed assessment according to international guidelines.

RESULTS

At baseline 0.5, 7.0, 41.7 and 50.8% reported a score of 0, 1, 2 and 3, respectively. During a mean follow-up time of 5.2 years, 7.1% (n = 188) of cognitively intact participants developed MCI and 3.0% (n = 79) developed dementia. Longitudinal analyses demonstrated that participants who had low SN were significantly more likely to have declines in MF (β = - 0.533, P = 0.014) compared to high SN. Social networks were not independently associated with the decline of SP and EF during follow-up. According to fully adjusted models using logistic regression, SN was significantly associated with incidence risk of MCI (OR = 2.030, P = 0.014 and OR = 1.847 P = 0.001). These associations were largely independent of other lifestyle factors, depression and genetic disposition.

CONCLUSIONS

Community-dwelling older adults who have poor social networks have a higher risk of declining memory function as well as a higher risk of mild cognitive impairment than older adults who have a higher social network. This study included numbers of relevant covariates in the study analysis, thereby significantly contributing to the literature on cognitive aging.

Circulating Metabolome and White Matter Hyperintensities in Women and Men

BACKGROUND

White matter hyperintensities (WMH), identified on T2-weighted magnetic resonance images of the human brain as areas of enhanced brightness, are a major risk factor of stroke, dementia, and death. There are no large-scale studies testing associations between WMH and circulating metabolites.

METHODS

We studied up to 9290 individuals (50.7% female, average age 61 years) from 15 populations of 8 community-based cohorts. WMH volume was quantified from T2-weighted or fluid-attenuated inversion recovery images or as hypointensities on T1-weighted images. Circulating metabolomic measures were assessed with mass spectrometry and nuclear magnetic resonance spectroscopy. Associations between WMH and metabolomic measures were tested by fitting linear regression models in the pooled sample and in sex-stratified and statin treatment-stratified subsamples. Our basic models were adjusted for age, sex, age×sex, and technical covariates, and our fully adjusted models were also adjusted for statin treatment, hypertension, type 2 diabetes, smoking, body mass index, and estimated glomerular filtration rate. Population-specific results were meta-analyzed using the fixed-effect inverse variance-weighted method. Associations with false discovery rate (FDR)-adjusted P values (PFDR)<0.05 were considered significant.

RESULTS

In the meta-analysis of results from the basic models, we identified 30 metabolomic measures associated with WMH (PFDR<0.05), 7 of which remained significant in the fully adjusted models. The most significant association was with higher level of hydroxyphenylpyruvate in men (PFDR.full.adj=1.40×10-7) and in both the pooled sample (PFDR.full.adj=1.66×10-4) and statin-untreated (PFDR.full.adj=1.65×10-6) subsample. In men, hydroxyphenylpyruvate explained 3% to 14% of variance in WMH. In men and the pooled sample, WMH were also associated with lower levels of lysophosphatidylcholines and hydroxysphingomyelins and a larger diameter of low-density lipoprotein particles, likely arising from higher triglyceride to total lipids and lower cholesteryl ester to total lipids ratios within these particles. In women, the only significant association was with higher level of glucuronate (PFDR=0.047).

CONCLUSIONS

Circulating metabolomic measures, including multiple lipid measures (eg, lysophosphatidylcholines, hydroxysphingomyelins, low-density lipoprotein size and composition) and nonlipid metabolites (eg, hydroxyphenylpyruvate, glucuronate), associate with WMH in a general population of middle-aged and older adults. Some metabolomic measures show marked sex specificities and explain a sizable proportion of WMH variance.

New insights into the genetic etiology of Alzheimer's disease and related dementias

Characterization of the genetic landscape of Alzheimer's disease (AD) and related dementias (ADD) provides a unique opportunity for a better understanding of the associated pathophysiological processes. We performed a two-stage genome-wide association study totaling 111,326 clinically diagnosed/'proxy' AD cases and 677,663 controls. We found 75 risk loci, of which 42 were new at the time of analysis. Pathway enrichment analyses confirmed the involvement of amyloid/tau pathways and highlighted microglia implication. Gene prioritization in the new loci identified 31 genes that were suggestive of new genetically associated processes, including the tumor necrosis factor alpha pathway through the linear ubiquitin chain assembly complex. We also built a new genetic risk score associated with the risk of future AD/dementia or progression from mild cognitive impairment to AD/dementia. The improvement in prediction led to a 1.6- to 1.9-fold increase in AD risk from the lowest to the highest decile, in addition to effects of age and the APOE ε4 allele.

Racial Residential Segregation in Young Adulthood and Brain Integrity in Middle Age: Can We Learn From Small Samples?

Racial residential segregation is associated with multiple adverse health outcomes in Black individuals. Yet, the influence of structural racism and racial residential segregation on brain aging is less understood. In this study, we investigated the association between cumulative exposure to racial residential segregation over 25 years (1985-2010) in young adulthood, as measured by the Getis-Ord Gi* statistic, and year 25 measures of brain volume (cerebral, gray matter, white matter, and hippocampal volumes) in midlife. We studied 290 Black participants with available brain imaging data who were enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) Study, a prospective cohort study. CARDIA investigators originally recruited 2,637 Black participants aged 18-30 years from 4 field centers across the United States. We conducted analyses using marginal structural models, incorporating inverse probability of treatment weighting and inverse probability of censoring weighting. We found that compared with low/medium segregation, greater cumulative exposure to a high level of racial residential segregation throughout young adulthood was associated with smaller brain volumes in general (e.g., for cerebral volume, β = -0.08, 95% confidence interval: -0.15, -0.02) and with a more pronounced reduction in hippocampal volume, though results were not statistically significant. Our findings suggest that exposure to segregated neighborhoods may be associated with worse brain aging.

Midlife alcohol consumption and later life cognitive impairment: Light drinking is not protective and APOE genotype does not change this relationship

Introduction

Much debate exists about the role of light to moderate alcohol intake and subsequent cognitive function. The apolipoprotein E genotype may modify the relationship.

Methods

Using data from the Honolulu-Asia Aging Study, a longitudinal population-based cohort (n = 2,416), Cox proportional hazards regression analyses were performed to measure midlife alcohol intake (average age = 52 years) and later life cognitive function (average age = 87 years) and to explore the role of apolipoprotein E genotype.

Results

No protective effect of light drinking (>1 drink/month– 1 drink/day) or moderate drinking (>1–2 drinks/day) was observed in the cohort in adjusted models (HR = 1.013, CI:0.88–1.16; HR = 1.104, CI:0.91–1.34, respectively). Heavy drinking (>2–4 drinks/day) and very heavy drinking (>4 drinks/day) increased the risk for incident moderate cognitive impairment (HR = 1.355, CI:1.09–1.68; HR = 1.462, CI:1.04–2.05, respectively). When examining the relationship by apolipoprotein E ε4 carrier status, a similar dose-response pattern was observed in both groups with higher hazard ratios for those carrying at least one copy of the apolipoprotein E ℇ4 allele. As alcohol level increased, the age at incident moderate cognitive impairment decreased, especially among those with at least one apolipoprotein E ℇ4 allele.

Discussion

We did not observe a significant protective effect for light to moderate drinking in midlife and subsequent cognitive impairment in this cohort. Heavy drinking increased the risk for moderate cognitive impairment and decreased the age at incidence, as did carrying at least one allele of the apolipoprotein E ℇ4 gene.

Mid-life epigenetic age, neuroimaging brain age, and cognitive function: coronary artery risk development in young adults (CARDIA) study

The proportion of aging populations affected by dementia is increasing. There is an urgent need to identify biological aging markers in mid-life before symptoms of age-related dementia present for early intervention to delay the cognitive decline and the onset of dementia. In this cohort study involving 1,676 healthy participants (mean age 40) with up to 15 years of follow up, we evaluated the associations between cognitive function and two classes of novel biological aging markers: blood-based epigenetic aging and neuroimaging-based brain aging. Both accelerated epigenetic aging and brain aging were prospectively associated with worse cognitive outcomes. Specifically, every year faster epigenetic or brain aging was on average associated with 0.19-0.28 higher (worse) Stroop score, 0.04-0.05 lower (worse) RAVLT score, and 0.23-0.45 lower (worse) DSST (all false-discovery-rate-adjusted p <0.05). While epigenetic aging is a more stable biomarker with strong long-term predictive performance for cognitive function, brain aging biomarker may change more dynamically in temporal association with cognitive decline. The combined model using epigenetic and brain aging markers achieved the highest accuracy (AUC: 0.68, p<0.001) in predicting global cognitive function status. Accelerated epigenetic age and brain age at midlife may aid timely identification of individuals at risk for accelerated cognitive decline and promote the development of interventions to preserve optimal functioning across the lifespan.

Genetic determinants of telomere length from 109,122 ancestrally diverse whole-genome sequences in TOPMed

Genetic studies on telomere length are important for understanding age-related diseases. Prior GWAS for leukocyte TL have been limited to European and Asian populations. Here, we report the first sequencing-based association study for TL across ancestrally-diverse individuals (European, African, Asian and Hispanic/Latino) from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program. We used whole genome sequencing (WGS) of whole blood for variant genotype calling and the bioinformatic estimation of telomere length in n=109,122 individuals. We identified 59 sentinel variants (p-value <5×10-9) in 36 loci associated with telomere length, including 20 newly associated loci (13 were replicated in external datasets). There was little evidence of effect size heterogeneity across populations. Fine-mapping at OBFC1 indicated the independent signals colocalized with cell-type specific eQTLs for OBFC1 (STN1). Using a multi-variant gene-based approach, we identified two genes newly implicated in telomere length, DCLRE1B (SNM1B) and PARN. In PheWAS, we demonstrated our TL polygenic trait scores (PTS) were associated with increased risk of cancer-related phenotypes.

Disentangling tau and brain atrophy cluster heterogeneity across the Alzheimer's disease continuum

Introduction

Neuroimaging heterogeneity in dementia has been examined using single modalities. We evaluated the associations of magnetic resonance imaging (MRI) atrophy and flortaucipir positron emission tomography (PET) clusters across the Alzheimer's disease (AD) spectrum.

Methods

We included 496 Alzheimer's Disease Neuroimaging Initiative participants with brain MRI, flortaucipir PET scan, and amyloid beta biomarker measures obtained. We applied a novel robust collaborative clustering (RCC) approach on the MRI and flortaucipir PET scans. We derived indices for AD‐like (SPARE‐AD index) and brain age (SPARE‐BA) atrophy.

Results

We identified four tau (I–IV) and three atrophy clusters. Tau clusters were associated with the apolipoprotein E genotype. Atrophy clusters were associated with white matter hyperintensity volumes. Only the hippocampal sparing atrophy cluster showed a specific association with brain aging imaging index. Tau clusters presented stronger clinical associations than atrophy clusters. Tau and atrophy clusters were partially associated.

Conclusions

Each neuroimaging modality captured different aspects of brain aging, genetics, vascular changes, and neurodegeneration leading to individual multimodal phenotyping.

Plasma Biomarkers of Angiogenesis Related to Small Vessel Brain Disease in SPRINT

Meta-analyses incorporating the Systolic Blood Pressure Intervention Trial (SPRINT) have shown a reduced incidence of dementia with blood pressure lowering. However, mechanistic explanations for this effect are lacking, apart from slowed progression of cerebral white matter lesions (WML). Here we examine possible biomarkers of angiogenesis related to small vessel brain disease including bFGF, FLT1, PLGF, TIE-2, VEGF, VEGF-C, and VEGF-D. The biomarkers were assayed in plasma at baseline and during follow-up (median follow-up = 3.8 years) in a subgroup of participants 60 to 89 years old from SPRINT (N=517). We modeled changes in each biomarker using robust linear mixed models accounting for treatment group, time since randomization, and kidney function. Participants were 69.8 ± 7.1 (standard deviation) years of age, 42.1% female, with a mean systolic blood pressure (SBP) of 138.2 ± 17.0 mm Hg. At baseline, none of the biomarkers were associated with WML lesion volume or total brain volumes adjusting for age (all p&gt;0.05), while FLT1, PLGF, and TIE-2 were negatively associated with frontal gray matter cerebral blood flow (partial correlations of -0.11, -0.10, and -0.12 respectively, all p&lt;0.05). For both intensive (target SBP&lt;120 mm Hg) and standard (target SBP&lt;140 m Hg) blood pressure control, mean levels for the majority of biomarkers increased during follow-up, with the exceptions of TIE-2 (decreased over follow-up) and VEGF-D (no change). We did not observe significant between-group differences for the change in these plasma biomarkers of angiogenesis comparing intensive to standard blood pressure treatment.

Social Participation and the Risk for Developing Mild Cognitive Impairment and Dementia Among Older Adults

Introduction: We aim to investigate the longitudinal associations between social participation and the risk of developing mild cognitive impairment (MCI|) and dementia over 5 years of follow-up among cognitively normal older adults. Methods: A total of 2802 participants had complete follow-up data from Age-Gene/Environment-Susceptibility-Reykjavik-Study. Social participation was assessed by a questionnaire asking the frequency of contact with children, relatives, friends and neighbors. MCI and dementia were diagnosed according to international guidelines and by a team composed of a geriatrician, neurologist, neuropsychologist, and neuroradiologist. Logistic regression analysis was used to assess the associations. Results: At baseline 8% (n=225) reported no social participation. Among cognitively normal participants at baseline, 5.6% (n=243) developed mild cognitive impairment and 2.4% (n= 103) developed dementia during a mean follow-up time of 5.2 years. After full adjustment with covariates including age, gender, education, marital status, vitamin D levels, depression and APOE ε4, those with no social participation at baseline were significantly more likely to develop MCI at follow-up (OR=1.953, P=0.001). However, social participation at baseline was not associated with higher dementia diagnosis at follow-up (OR= 1.490, P=0.194). Conclusions: Community-dwelling old adults who are socially inactive are more likely to develop MCI than those who are socially active. Social participation might independently indicate impending changes in cognitive function among older adults.

The Association between Leisure and Physical Activity Level with Depressive Symptoms after 5-years of follow-up

BACKGROUND: Depressive symptoms in older adults are associated with socioeconomic status (SES), medical care, and physical activity. However, there is little evidence on the longitudinal association between level of leisure activity (LA) and physical activity (PA) with depressive symptoms among community-dwelling older adults in Iceland. The study examined an association of LA and PA at baseline with high depressive symptoms (HGDS) assessed after 5 years of follow-up among community-dwelling older adults. METHODS: A large community-based population residing in Reykjavik, Iceland participated in a longitudinal study with 5 years of follow-up (n=2957, 58% women, 74.9±4.8 yrs). Those with HGDS or dementia at baseline were excluded from the analysis. The reported activity was categorized into 2 groups as no-activity versus any-activity. Depressive symptoms were assessed by the 15-item Geriatric Depression Scale (GDS) on average 5 years later. RESULTS: After adjusting for demographic and health-related risk factors, those who reported having any LA had significantly fewer HGDS after the follow-up of 5 years (6 or higher GDS scores, Odds Ratio (OR) = 0.46, 95% Confidence Interval (CI): 0.27 ~ 0.76, P = 0.003). However, reporting any PA at baseline was not significantly associated with HGDS (OR = 0.71, 95% CI: 0.51 ~ 1.00, P = 0.053). CONCLUSION: Our study shows that any LA among older adults is associated with having less depressive symptoms 5 years later among community-dwelling older adults while having any PA was not associated with depressive symptoms after 5 years of follow-up.

Exploratory assessment of pineal gland volume, composition, and urinary 6-sulfatoxymelatonin levels on prostate cancer risk

INTRODUCTION

Melatonin levels are partially driven by the parenchyma volume of the pineal gland. Low urinary levels of 6-sulfatoxymelatonin have been associated with increased risk of advanced prostate cancer, but the relationship between pineal gland volume and composition and prostate cancer risk has not been examined.

MATERIALS AND METHODS

We utilized data from 864 men from the AGES-Reykjavik Study with complete pineal gland volumes and urinary 6-sulfatoxymelatonin measurements. Pineal parenchyma, calcification, and cyst volumes were calculated from brain magnetic resonance imaging. Levels of 6-sulfatoxymelatonin were assayed from prediagnostic urine samples. We calculated Pearson correlation coefficients between parenchyma volume and urinary 6-sulfatoxymelatonin levels. We used Cox proportional hazards regression to calculate multivariable hazard ratios (HRs) and 95% confidence intervals (95% CIs) comparing prostate cancer risk across parenchyma volume tertiles and across categories factoring in parenchyma volume, gland composition, and urinary 6-sulfatoxymelatonin level.

RESULTS

Parenchyma volume was moderately correlated with urinary 6-sulfatoxymelatonin level (r = .24; p < .01). There was no statistically significant association between parenchyma volume tertile and prostate cancer risk. Men with high parenchyma volume, pineal cysts and calcifications, and low urinary 6-sulfatoxymelatonin levels had almost twice the risk of total prostate cancer as men with low parenchyma volume, no pineal calcifications or cysts, and low urinary 6-sulfatoxymelatonin levels (HR: 1.98; 95% CI: 1.02, 3.84; p: .04).

CONCLUSIONS

Although parenchyma volume is not associated with prostate cancer risk, pineal gland composition and other circadian dynamics may influence risk for prostate cancer. Additional studies are needed to examine the interplay of pineal gland volume, composition, and melatonin levels on prostate cancer risk.

Associations between 20-year lipid variability throughout young adulthood and midlife cognitive function and brain integrity

BACKGROUND

Little is known about long-term lipid variability in young adulthood in relation to cognitive function and brain integrity in midlife.

METHODS

We studied 3,328 adults from the Coronary Artery Risk Development in Young Adults. We defined low- and high- density lipoprotein (LDL, HDL) variability as the intra-individual standard deviation of lipid measurements over 20 years of young adulthood (1985-2005). Cognitive tests were administered in 2010. Brain scans were performed in 2010 on 714 participants. To facilitate comparison, cognitive tests and brain metrics were z-scored.

RESULTS

Mean age at baseline was 25.4 years. Higher 20-year LDL variability was associated with worse verbal memory in midlife (β=-0.25, 95% CI [-0.42, -0.08]), adjusted for important covariates. Higher 20-year HDL variability was associated with worse processing speed in midlife (β=-0.80, 95% CI [-1.18, -0.41]) and brain integrity, e.g. smaller total brain volume (β=-0.58, 95% CI [-0.82, -0.34]) and worse total brain fractional anisotropy (β=-1.13, 95% CI [-1.87, -0.39]).

CONCLUSIONS

Higher long-term lipid variability in adulthood was associated with worse cognition and brain integrity in midlife, in a relatively young cohort.

Association of Racial Residential Segregation Throughout Young Adulthood and Cognitive Performance in Middle-aged Participants in the CARDIA Study

Importance

Neighborhood-level residential segregation is implicated as a determinant for poor health outcomes in black individuals, but it is unclear whether this association extends to cognitive aging, especially in midlife.

Objective

To examine the association between cumulative exposure to residential segregation during 25 years of young adulthood among black individuals and cognitive performance in midlife.

Design, Setting, and Participants

The ongoing prospective cohort Coronary Artery Risk Development in Young Adults (CARDIA) Study recruited 5115 black and white participants aged 18 to 30 years from 4 field centers at the University of Alabama, Birmingham; University of Minnesota, Minneapolis; Northwestern University, Chicago, Illinois; and Kaiser Permanente, Oakland, California. Data were acquired from February 1985 to May 2011. Among the surviving CARDIA cohort, 3671 (71.8%) attended examination year 25 of the study in 2010, when cognition was measured, and 3008 (81.9%) of those completed the cognitive assessments. To account for time-varying confounding and differential censoring, marginal structural models using inverse probability weighting were applied. Data were analyzed from April 16 to July 20, 2019.

Main Outcomes and Measures

Racial residential segregation was measured using the Getis-Ord Gi* statistic, and the mean cumulative exposure to segregation was calculated across 6 follow-up visits from baseline to year 25 of the study, then categorized into high, medium, and low segregation. Cognitive function was measured at year 25 of the study, using the Digit Symbol Substitution Test (DSST), Stroop color test (reverse coded), and Rey Auditory Verbal Learning Test. To facilitate comparison of estimates, z scores were calculated for all cognitive tests.

Results

A total of 1568 black participants with available cognition data were included in the analysis. At baseline, participants had a mean (SD) age of 25 (4) years and consisted of 936 women (59.7%). Greater cumulative exposure to segregated neighborhoods was associated with a worse DSST z score (for high segregation, β = -0.37 [95% CI, -0.61 to -0.13]; for medium segregation, β = -0.25 [95% CI, -0.51 to 0.0002]) relative to exposure to low segregation.

Conclusions and Relevance

In this cohort study, exposure to residential segregation throughout young adulthood was associated with worse processing speed among black participants as early as in midlife. This association may potentially explain black-white disparities in dementia risk at older age.

Computed tomography-based skeletal muscle and adipose tissue attenuation: Variations by age, sex, and muscle

OBJECTIVE

This study aimed to investigate how skeletal muscle attenuation and adipose tissue (AT) attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle vary according to the targeted muscles, sex, and age.

DESIGN

Population-based cross-sectional study.

SETTING

Community-dwelling old population in Reykjavik, Iceland.

SUBJECTS

A total of 5331 older adults (42.8% women), aged 66-96 years from the Age, Gene/Environment Susceptibility (AGES)- Reykjavik Study, who participated in the baseline visit (between 2002 and 2006) and had valid thigh and abdominal computed tomography (CT) scans were studied.

METHODS

Muscle attenuation and AT attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle were determined using CT. Linear mixed model analysis of variance was performed for each sex, with skeletal muscle or AT attenuation as the dependent variable.

RESULTS

Muscle attenuation decreased, and AT attenuation increased with age in both sexes, and these differences were specific for each muscle, although not in all age groups. Age-related differences in muscle and AT attenuation varied with specific muscle. In general, for both sexes, skeletal muscle attenuation of the hamstrings declined more than average with age. Men and women displayed a different pattern in the age differences in AT attenuation for each muscle.

CONCLUSIONS

Our data support the hypotheses that skeletal muscle attenuation decreases, and AT attenuation increases with aging. In addition, our data add new evidence, supporting that age-related differences in skeletal muscle and AT attenuation vary between muscles.

Diffuse idiopathic skeletal hyperostosis in elderly Icelanders and its association with the metabolic syndrome: the AGES-Reykjavik Study

Objective: To describe the prevalence of diffuse idiopathic skeletal hyperostosis (DISH) in a large population-based study of elderly Icelanders, with particular reference to weight-related factors and the metabolic syndrome.Method: The study population comprised 5321 participants aged 68-96 years (2276 males, mean ± sd age 76 ± 5 , and 3045 females, age 77 ± 6) from the AGES-Reykjavik Study. DISH diagnosis was based on computed tomography (CT) scans, and interpreted strictly by the Resnick criteria and additional suggestions for CT interpretation by Oudkerk et al. Radiology readings were taken by a radiology resident and sample readings by two experienced radiologists.Results: A diagnosis of DISH was made in 13.7% of males and 2.8% of females. There was no association with age, but a strong association was seen with the metabolic syndrome [odds ratio (OR) 2.12, 95% confidence interval (CI) 1.69-2.64, p = 3.9 × 10^-11]. Among the components of the metabolic syndrome, the association with DISH was significant for the insulin resistance criterion (OR 1.66, 95% CI 1.32-2.01, p < 0.001) and the body mass index (BMI) criterion (OR 2.16, 95% CI 1.70-2.74, p < 0.001). Other weight-related variables (midlife BMI, weight, and abdominal circumference) showed similar associations.Conclusions: This study, which to our knowledge is the largest published study on the prevalence of DISH, shows an association with the metabolic syndrome, particularly with the insulin resistance and BMI criteria. This is analogous with previous reports linking DISH with metabolic causes. In this age category, we did not observe any increase in prevalence with age.

Body weight changes and longitudinal associations with cognitive decline among community-dwelling older adults

INTRODUCTION

We aim to investigate the longitudinal associations between changes in body weight (BW) and declines in cognitive function and risk of mild cognitive impairment (MCI)/dementia among cognitively normal individuals 65 years or older.

METHODS

Data from the Age Gene/Environment Susceptibility-Reykjavik Study (AGES-Reykjavik Study) including 2620 participants, were examined using multiple logistic regression models. Cognitive function included speed of processing (SP), executive function (EF), and memory function (MF). Changes in BW were classified as; weight loss (WL), weight gain (WG), and stable weight (SW).

RESULTS

Mean follow-up time was 5.2 years and 61.3% were stable weight. Participants who experienced WL (13.4%) were significantly more likely to have declines in MF and SP compared to the SW group. Weight changes were not associated with EF. WL was associated with a higher risk of MCI, while WG (25.3%) was associated with a higher dementia risk, when compared to SW.

DISCUSSION

Significant BW changes in older adulthood may indicate impending changes in cognitive function.

Sedentary Behavior, Brain-Derived Neurotrophic Factor (BDNF), and Brain Structure in Midlife: A Brain MRI Study

Long sedentary time (ST) is associated with poor brain health but the underlying mechanisms are unclear. Studies suggest exercise increases BDNF levels, and that low BDNF levels are associated with cognitive impairment. Limited population-based studies have examined associations among sedentary behavior (SB), BDNF, and brain structures. Here we explore the mediation and interaction effect of BDNF in the association of SB to brain measures. We included 612 participants from the MRI sub-study of the Coronary Artery Risk Development in Young Adults who had plasma BDNF and SB data at the Year 25 examination. SB was estimated by self-reported average ST hours/day spent sitting while watching television, using computers, and riding transportation. Outcome measures were total and selected brain volumes in cubic centimeters (cc). ST was categorized into quartiles. We used general linear regression to examine the following associations, adjusting for age, sex, race, and intracranial volume: Interactions between BDNF and ST on MRI; ST and MRI; ST and BDNF; BDNF and MRI; and ST, BDNF, and MRI. People in the upper 25%ile ST (&gt;8.4 hours/day) had a decreased TB volume of 12.2 cc (p=0.01) compared to the lower 25%ile (&lt;4.3 hours/day). Neither ST nor brain measures were associated with BDNF (p&gt;0.05). Instead, BDNF interacted with ST for TB and WM (p &lt; 0.03): The difference of brain volumes between the upper and lower 25%ile decreased with increasing BDNF levels. Accordingly, higher BDNF levels may protect brain function in the middle-aged and potentially older populations with a sedentary lifestyle.

Longitudinal Association Between Education and Disability in Older Adults Living in Iceland

BACKGROUND: Disabilities among older adults are associated with cumulative adversities such as low socioeconomic status (SES), poor nutrition, and lack of access to medical care and education. However, there is little evidence on the long-term association between education and disability status among older adults in Iceland. The aim of the study was to examine the association between mid-life education and prevalence of disability in activities of daily living (ADL) and mobility disability in late-life using 25 years of longitudinal data. METHODS: A large community-based population residing in Reykjavik, Iceland participated in a longitudinal study with an average of 25 years of follow-up (N=5764, mean age 77±6 yrs, 57.7% of women) Mid-life education was categorized into 2 groups (primary and secondary versus college and university). Disability status in late life was defined with ADL and mobility disability with a binary outcome (no difficulty versus any difficulty). Logistic regression analysis was used to examine the association. RESULTS: After controlling for age and gender, and midlife health risk factors, those who had high education at mid-life were less likely to have ADL disability (Odds Ratio (OR) = 0.75, 95% Confidence Interval (CI): 0.64 ~ 0.88, P ≤ 0.001) and mobility disability (OR = 0.72, 95% CI: 0.61 ~ 0.86, P < 0.001) compared with those who had low education in mid-life. CONCLUSION: People with high mid-life education were less likely to have ADL and mobility disability after 25 years later.

Lifestyle and 25-hydroxy-vitamin D among community-dwelling old adults with dementia, mild cognitive impairment, or normal cognitive function

BACKGROUND

Several studies have indicated that older adults with cognitive impairment have a poorer lifestyle than their healthy peers including lower 25-hydroxy-vitamin D levels (25OHD).

AIM

To investigate the associations between lifestyle and 25OHD depending on cognitive status among old adults.

METHODS

Community-dwelling old adults (65-96 years) participated in this cross-sectional study based on the Age-Gene/Environment-Susceptibility-Reykjavik-Study. The analytical sample included 5162 subjects who were stratified by cognitive status, i.e., dementia (n = 307), mild cognitive impairment (MCI, n = 492), and normal cognitive status (NCS, n = 4363). Lifestyle variables were assessed and 25OHD was measured. The associations between lifestyle and 25OHD were calculated using linear models correcting for potential confounders.

RESULTS

According to linear regression models, 25OHD was significantly lower in older people with dementia (53.8 ± 19.6 nmol/L) than in NCS participants (57.6 ± 17.7 nmol/L). Cod liver oil (7.1-9.2 nmol/L, P < 0.001) and dietary supplements (4.4-11.5 nmol/L, P < 0.001) were associated with higher 25OHD in all three groups. However, physical activity ≥ 3 h/week (2.82 nmol/L, P < 0.001), BMI < 30 kg/m² (5.2 nmol/L, P < 0.001), non-smoking (4.8 nmol/L, P < 0.001), alcohol consumption (2.7 nmol/L, P < 0.001), and fatty fish consumption ≥ 3x/week (2.6 nmol/L, P < 0.001) were related to higher 25OHD in NCS only, but not in participants with dementia or MCI.

DISCUSSION

Older people living in Iceland with dementia are at higher risk for 25OHD deficiency when compared to healthy individuals. Physical activity reported among participants with dementia, and MCI is low and is not significantly associated with 25OHD.

CONCLUSIONS

Lifestyle factors among NCS participants are associated with 25OHD levels. Importantly, healthy lifestyle should be promoted among individuals with MCI and dementia.

Cigarette Smoking Is Associated With Lower Quadriceps Cross-sectional Area and Attenuation in Older Adults

INTRODUCTION

In addition to well-established links with cardiovascular and respiratory diseases, cigarette smoking may affect skeletal muscle; however, associations with quadriceps atrophy, density, and function are unknown. This study explored the associations of current and former smoking with quadriceps muscle area and attenuation as well as muscle force (assessed as knee extension peak torque) and rate of torque development-a measure of muscle power in older adults.

METHODS

Data from 4469 older adults, aged 66-95 years at baseline in the Age, Gene/Environment Susceptibility-Reykjavik Study with measurements of thigh computed tomography, isometric knee extension testing, self-reported smoking history, and potential covariates were analyzed.

RESULTS

Sex differences were observed in these data; therefore, our final analyses are stratified by sex. In men, both former smokers and current smokers had lower muscle area (with β= -0.10, 95% confidence interval [CI] = -0.17 to -0.03 and β = -0.19, 95% CI = -0.33 to -0.05, respectively) and lower muscle attenuation (ie, higher fat infiltration, β = -0.08, 95% CI = -0.16 to -0.01 and β = -0.17, 95% CI = -0.34 to -0.01, respectively) when compared with never smokers. Smoking status was not associated with male peak torque or rate of torque development. In women, current smoking was associated with lower muscle attenuation (β = -0.24, 95% CI = -0.34 to -0.13) compared to never smoking. Among female smokers (current and former), muscle attenuation and peak torque were lower with increasing pack-years.

CONCLUSIONS

Results suggest that cigarette smoking is related to multiple muscle properties at older age and that these relationships may be different among men and women.

IMPLICATIONS

This article presents novel data, as it examined for the first time the relationship between smoking and computed tomography-derived quadriceps muscle size (cross-sectional area) and attenuation. This study suggests that current cigarette smoking is related to higher muscle fat infiltration, which may have significant health implications for the older population, because of its known association with poor physical function, falls, and hip fractures.

Complex Walking Tasks and Risk for Cognitive Decline in High Functioning Older Adults

BACKGROUND

Performance on complex walking tasks may provide a screen for future cognitive decline.

OBJECTIVE

To identify walking tasks that are most strongly associated with subsequent cognitive decline.

METHODS

Community-dwelling older adults with Modified Mini-Mental State (3MS) >85 at baseline (n = 223; mean age = 78.7, 52.5% women, 25.6% black) completed usual-pace walking and three complex walking tasks (fast-pace, narrow-path, visuospatial dual-task). Slope of 3MS scores for up to 9 subsequent years (average = 5.2) were used to calculate a cognitive maintainer (slope ≥0) or decliner (slope <0) outcome variable. Logistic regression models assessed associations between gait speeds and being a cognitive decliner. A sensitivity analysis in a subsample of individuals (n = 66) confirmed results with adjudicated mild cognitive impairment (MCI) or dementia at 8-9 years post-walking assessment.

RESULTS

Cognitive decliners were 52.5% of the sample and on average were slower for all walking tasks compared to maintainers. In models adjusted for demographic and health variables, faster fast-pace (OR = 0.87 per 0.1 m/s, 95% CI: 0.78, 0.97) and dual-task (OR = 0.84 per 0.1 m/s, 95% CI: 0.73, 0.96) gait speeds were associated with lower likelihood of being a cognitive decliner. Usual-pace gait speed was not associated (OR = 0.96 per 0.1 m/s, 95% CI: 0.85, 1.08). Results were nearly identical in analyses with adjudicated MCI or dementia as the outcome.

CONCLUSION

Fast-pace and dual-task walking may provide simple and effective tools for assessing risk for cognitive decline in older individuals with high cognitive function. Such screening tools are important for strategies to prevent or delay onset of clinically meaningful change.

Twenty-seven-year time trends in dementia incidence in Europe and the United States: The Alzheimer Cohorts Consortium

OBJECTIVE

To determine changes in the incidence of dementia between 1988 and 2015.

METHODS

This analysis was performed in aggregated data from individuals >65 years of age in 7 population-based cohort studies in the United States and Europe from the Alzheimer Cohort Consortium. First, we calculated age- and sex-specific incidence rates for all-cause dementia, and then defined nonoverlapping 5-year epochs within each study to determine trends in incidence. Estimates of change per 10-year interval were pooled and results are presented combined and stratified by sex.

RESULTS

Of 49,202 individuals, 4,253 (8.6%) developed dementia. The incidence rate of dementia increased with age, similarly for women and men, ranging from about 4 per 1,000 person-years in individuals aged 65-69 years to 65 per 1,000 person-years for those aged 85-89 years. The incidence rate of dementia declined by 13% per calendar decade (95% confidence interval [CI], 7%-19%), consistently across studies, and somewhat more pronouncedly in men than in women (24% [95% CI 14%-32%] vs 8% [0%-15%]).

CONCLUSION

The incidence rate of dementia in Europe and North America has declined by 13% per decade over the past 25 years, consistently across studies. Incidence is similar for men and women, although declines were somewhat more profound in men. These observations call for sustained efforts to finding the causes for this decline, as well as determining their validity in geographically and ethnically diverse populations.

Common Genetic Variation Indicates Separate Causes for Periventricular and Deep White Matter Hyperintensities

BACKGROUND AND PURPOSE

Periventricular white matter hyperintensities (WMH; PVWMH) and deep WMH (DWMH) are regional classifications of WMH and reflect proposed differences in cause. In the first study, to date, we undertook genome-wide association analyses of DWMH and PVWMH to show that these phenotypes have different genetic underpinnings.

METHODS

Participants were aged 45 years and older, free of stroke and dementia. We conducted genome-wide association analyses of PVWMH and DWMH in 26,654 participants from CHARGE (Cohorts for Heart and Aging Research in Genomic Epidemiology), ENIGMA (Enhancing Neuro-Imaging Genetics Through Meta-Analysis), and the UKB (UK Biobank). Regional correlations were investigated using the genome-wide association analyses -pairwise method. Cross-trait genetic correlations between PVWMH, DWMH, stroke, and dementia were estimated using LDSC.

RESULTS

In the discovery and replication analysis, for PVWMH only, we found associations on chromosomes 2 (NBEAL), 10q23.1 (TSPAN14/FAM231A), and 10q24.33 (SH3PXD2A). In the much larger combined meta-analysis of all cohorts, we identified ten significant regions for PVWMH: chromosomes 2 (3 regions), 6, 7, 10 (2 regions), 13, 16, and 17q23.1. New loci of interest include 7q36.1 (NOS3) and 16q24.2. In both the discovery/replication and combined analysis, we found genome-wide significant associations for the 17q25.1 locus for both DWMH and PVWMH. Using gene-based association analysis, 19 genes across all regions were identified for PVWMH only, including the new genes: CALCRL (2q32.1), KLHL24 (3q27.1), VCAN (5q27.1), and POLR2F (22q13.1). Thirteen genes in the 17q25.1 locus were significant for both phenotypes. More extensive genetic correlations were observed for PVWMH with small vessel ischemic stroke. There were no associations with dementia for either phenotype.

CONCLUSIONS

Our study confirms these phenotypes have distinct and also shared genetic architectures. Genetic analyses indicated PVWMH was more associated with ischemic stroke whilst DWMH loci were implicated in vascular, astrocyte, and neuronal function. Our study confirms these phenotypes are distinct neuroimaging classifications and identifies new candidate genes associated with PVWMH only.

The genetic architecture of the human cerebral cortex

The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder.

Incident prolonged QT interval in midlife and late-life cognitive performance

BACKGROUND

Measures of cardiac ventricular electrophysiology have been associated with cognitive performance in cross-sectional studies. We sought to evaluate the association of worsening ventricular repolarization in midlife, as measured by incident prolonged QT interval, with cognitive decline in late life.

METHODS

Midlife QT interval was assessed by electrocardiography during three study visits from 1965/68 to 1971/74 in a cohort of Japanese American men aged 46-68 at Exam 1 from the Honolulu Heart Study. We defined incident prolonged QT as the QT interval in the upper quartile at Exam 2 or 3 after QT interval in lower three quartiles at Exam 1. Cognitive performance was assessed at least once using the Cognitive Abilities Screening Instrument (CASI), scored using item response theory (CASI-IRT), during four subsequent visits from 1991/93 to 1999/2000 among 2,511 of the 4,737 men in the Honolulu-Asia Aging Study otherwise eligible for inclusion in analyses. We used marginal structural modeling to determine the association of incident prolonged QT with cognitive decline, using weighting to account for confounding and attrition.

RESULTS

Incident prolonged QT interval in midlife was not associated with late-life CASI-IRT at cognitive baseline (estimated difference in CASI-IRT: 0.04; 95% CI: -0.28, 0.35; p = 0.81), or change in CASI-IRT over time (estimated difference in annual change in CASI-IRT: -0.002; 95%CI: -0.013, 0.010; p = 0.79). Findings were consistent across sensitivity analyses.

CONCLUSIONS

Although many midlife cardiovascular risk factors and cardiac structure and function measures are associated with late-life cognitive decline, incident prolonged QT interval in midlife was not associated with late-life cognitive performance or cognitive decline.

Associations of Quadriceps Torque Properties with Muscle Size, Attenuation, and Intramuscular Adipose Tissue in Older Adults

Background

Atrophy and fatty infiltration of muscle with aging are associated with fractures and falls, however, their direct associations with muscle function are not well described. It was hypothesized that participants with lower quadriceps muscle attenuation, area, and greater intramuscular adipose tissue (IMAT) will exhibit slower rates of torque development (RTD) and lower peak knee extension torques.

Methods

Data from 4,842 participants (2,041 men, 2,801 women) from the Age Gene/Environment Susceptibility Reykjavik Study (mean age 76 ± 0.1 years) with complete thigh computed tomography and isometric knee testing. Regression models were adjusted for health, behavior, and comorbidities. Muscle attenuation was further adjusted for muscle area and IMAT; muscle area adjusted for IMAT and attenuation; and IMAT adjusted for muscle area and attenuation. Standardized betas (β) indicate association effect sizes.

Results

In the fully-adjusted models, attenuation (men β = 0.06, 95% CI: 0.01, 0.11; women β = 0.07, 95% CI: 0.03, 0.11) and muscle area (men β = 0.13, 95% CI: 0.07, 0.19; women β = 0.10, 95% CI: 0.06, 0.15) were associated with knee RTD. Attenuation (men β = 0.12, 95% CI: 0.08, 0.16; women β = 0.12, 95% CI: 0.09, 0.16) and muscle area (men β = 0.38, 95% CI: 0.33, 0.43; women β = 0.33, 95% CI: 0.29, 0.37) were associated with peak torque.

Conclusions

These data suggest that muscle attenuation and area are independently associated with RTD and peak torque; and that area and attenuation demonstrate similar contributions to RTD.

The impact of APOE genotype on survival: Results of 38,537 participants from six population-based cohorts (E2-CHARGE)

BACKGROUND

Apolipoprotein E is a glycoprotein best known as a mediator and regulator of lipid transport and uptake. The APOE-ε4 allele has long been associated with increased risks of Alzheimer's disease and mortality, but the effect of the less prevalent APOE-ε2 allele on diseases in the elderly and survival remains elusive.

METHODS

We aggregated data of 38,537 individuals of European ancestry (mean age 65.5 years; 55.6% women) from six population-based cohort studies (Rotterdam Study, AGES-Reykjavik Study, Cardiovascular Health Study, Health-ABC Study, and the family-based Framingham Heart Study and Long Life Family Study) to determine the association of APOE, and in particular APOE-ε2, with survival in the population.

RESULTS

During a mean follow-up of 11.7 years, 17,021 individuals died. Compared with homozygous APOE-ε3 carriers, APOE-ε2 carriers were at lower risk of death (hazard ratio,95% confidence interval: 0.94,0.90-0.99; P = 1.1*10-2), whereas APOE-ε4 carriers were at increased risk of death (HR 1.17,1.12-1.21; P = 2.8*10-16). APOE was associated with mortality risk in a dose-dependent manner, with risk estimates lowest for homozygous APOE-ε2 (HR 0.89,0.74-1.08), and highest for homozygous APOE-ε4 (HR 1.52,1.37-1.70). After censoring for dementia, effect estimates remained similar for APOE-ε2 (HR 0.95,0.90-1.01), but attenuated for APOE-ε4 (HR 1.07,1.01-1.12). Results were broadly similar across cohorts, and did not differ by age or sex. APOE genotype was associated with baseline lipid fractions (e.g. mean difference(95%CI) in LDL(mg/dL) for ε2 versus ε33: -17.1(-18.1-16.0), and ε4 versus ε33: +5.7(4.8;6.5)), but the association between APOE and mortality was unaltered after adjustment for baseline LDL or cardiovascular disease. Given the European ancestry of the study population, results may not apply to other ethnicities.

CONCLUSION

Compared with APOE-ε3, APOE-ε2 is associated with prolonged survival, whereas mortality risk is increased for APOE-ε4 carriers. Further collaborative efforts are needed to unravel the role of APOE and in particular APOE-ε2 in health and disease.

Abstract 5045: Pineal gland volume and risk of prostate cancer

Background: The parenchyma of the pineal gland, an endocrine gland in the brain, produces the circadian hormone melatonin. Previously, we found low levels of melatonin were associated with an increased risk for advanced prostate cancer. This study used data from men in the Age, Gene/Environment Susceptibility-Reykjavik (AGES-Reykjavik) Study to evaluate the relationship between pineal volume, melatonin levels, and prostate cancer risk.

Methods: Participants were enrolled in the AGES-Reykjavik Study from 2002 to 2006 and underwent detailed clinical assessments at baseline that included biospecimen collection, MRI of the brain, medical history, and health questionnaires on dietary and lifestyle factors. We included 802 men who had information on pineal size, where parenchyma, calcification, and cyst volume were estimated individually and manually from the MRIs. Cox proportional hazards regression was used to calculate hazard ratios and 95% confidence intervals for risk of prostate cancer during follow-up through 2014, comparing parenchyma volume tertiles.

Results: There was a positive association between pineal parenchyma volume and urinary levels of melatonin. During follow-up, 135 men were diagnosed with prostate cancer, 30 of which were advanced prostate cancer. Men with volumes in the upper tertile had no statistically significant increased risk of prostate cancer compared to men with volumes in the lowest tertile (HR: 1.0, 95% CI: 0.7, 1.5), and men with volumes in the middle tertile had only a borderline statistically significant decreased risk of prostate cancer compared to men with volumes in the lowest tertile (HR: 0.7, 95% CI: 0.4, 1.0). Compared to men without pineal cysts, there was a borderline statistically significant association between men with pineal cysts and decreased risk of prostate cancer (HR: 0.7, 95% CI: 0.5, 1.0). Compared to men without pineal calcifications, there was no statistically significant association between men with pineal calcifications and increased risk of prostate cancer (HR: 1.1, 95% CI: 0.7, 1.6).

Conclusions: Pineal parenchyma volume was associated with melatonin levels, but there was no statistically significant association between parenchyma volume alone and prostate cancer risk. Further studies are needed to investigate the relationship between pineal parenchyma volume, presence of calcifications and cysts, melatonin, and prostate cancer.

Citation Format: Latifa A. Bazzi, Lara Sigurdardottir, Sigurdur Sigurdsson, Unnur Valdimarsdottir, Johanna Torfadottir, Thor Aspelund, Lenore Launer, Tamara Harris, Vilmundur Gudnason, Lorelei Mucci, Sarah Markt. Pineal gland volume and risk of prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5045.

Author Correction: Study of 300,486 individuals identifies 148 independent genetic loci influencing general cognitive function

Christina M. Lill, who contributed to analysis of data, was inadvertently omitted from the author list in the originally published version of this article. This has now been corrected in both the PDF and HTML versions of the article.

Abstract WP216: Epigenome-Wide Association Study of Cerebral White Matter Hyperintensities

Background: Cerebral white matter hyperintensities (WMH) on MRI are typical markers of small vessel disease and strong radiological correlates of stroke and age-related cognitive decline. Despite a recognized high heritability, the molecular basis of WMH has not been fully characterized. In particular, the contribution of epigenetic modifications, such as DNA methylation, has not been explored.

Methods: We conducted a meta-analysis of epigenome-wide association studies of WMH burden in up to 5777 elderly participants of European and African ancestry from 9 population-based cohorts using blood-derived DNA methylation measured on the Infinium HumanMethylation450 BeadChip. Cohort-specific associations between burden of WMH and DNA methylation beta values were estimated using linear mixed-effect models and combined in a sample-size weighted fixed-effect meta-analysis. In addition, we used two different approaches to identify differentially methylated regions (DMRs), which may be more informative than individual loci. Bonferroni correction and False Discovery Rates were used to account for the multiple tests.

Results: Single-site analyses identified a CpG site within the CLDN5 gene significantly associated with WMH (P= 2.3x10 -7 ). Claudin-5 is an endothelial-specific component in the brain vasculature and regulates blood brain barrier permeability. Region-based analyses, which leverage the correlations between nearby CpG sites identified several DMRs significantly associated with WMH burden including: PRMT1, BTBD17, and IFITM10 (P=1.4x10 -10 , 2.3x10 -8 , and 3.6x10 -7 , respectively). PRMT1 encodes the Protein Arginine N-methylase 1, which methylates histones in genes involved in glioblastomagenesis. Mice lacking this gene are characterized by severe defects in oligodendrocyte maturation processes. The function of BTBD17 and IFITM10 is not characterized but both are expressed in the brain and exhibit changes in expression in response to viral infection.

Conclusions: Consistent with our previously reported genetic association studies, this genome-wide DNA methylation analysis supports a role of genes involved in glial cell function in WMH etiology. It also suggests a novel role of genes involved in viral response.

Sex differences in the spatial distribution of bone in relation to incident hip fracture: Findings from the AGES-Reykjavik study

In this case-cohort study, we used data-driven computational anatomy approaches to assess within and between sex spatial differences in proximal femoral bone characteristics in relation to incident hip fracture. One hundred male and 234 female incident hip fracture cases, and 1047 randomly selected noncase subcohort participants (562 female) were chosen from the population-based AGES-Reykjavik study (mean age of 77 years). The baseline -i.e. before hip fracture- hip quantitative computed tomography scans of these subjects were analyzed using voxel-based morphometry, tensor-based morphometry, and surface-based statistical parametric mapping to assess the spatial distribution of volumetric bone mineral density (vBMD), internal structure, and cortical bone properties (thickness, vBMD and trabecular vBMD adjacent to the endosteal surface) of the proximal femur, respectively, in relation to incident hip fracture. Results showed that in both men and women: 1) the superior aspect of the femoral neck and the trochanteric region (except for cortical bone thickness) were consistently identified as being associated with incident hip fracture, and 2) differences in bone properties between noncases and incident hip fracture cases followed similar trends, were located at compatible regions, and manifested heterogeneity in the spatial distribution of their magnitude with focal regions showing larger differences. With respect to sex differences, most of the regions with a significant interaction between fracture group and sex showed: 1) differences of greater magnitude in men between noncases and incident hip fracture cases with different spatial distributions for all bone properties with the exception of cortical bone thickness, and 2) that while most of these regions showed better bone quality in male cases than in female cases, female cases showed higher vBMD in the principal compressive group and higher endotrabecular vBMD at several regions including the anterior, posterior, and lateral aspects of the proximal femur. These findings indicate the value of these image analysis techniques by providing unique information about the specific patterns of bone deterioration associated with incident hip fracture and their sex differences, highlighting the importance of looking to men and women separately in the assessment of hip fracture risk.

Study of 300,486 individuals identifies 148 independent genetic loci influencing general cognitive function

General cognitive function is a prominent and relatively stable human trait that is associated with many important life outcomes. We combine cognitive and genetic data from the CHARGE and COGENT consortia, and UK Biobank (total N = 300,486; age 16-102) and find 148 genome-wide significant independent loci (P < 5 × 10-8) associated with general cognitive function. Within the novel genetic loci are variants associated with neurodegenerative and neurodevelopmental disorders, physical and psychiatric illnesses, and brain structure. Gene-based analyses find 709 genes associated with general cognitive function. Expression levels across the cortex are associated with general cognitive function. Using polygenic scores, up to 4.3% of variance in general cognitive function is predicted in independent samples. We detect significant genetic overlap between general cognitive function, reaction time, and many health variables including eyesight, hypertension, and longevity. In conclusion we identify novel genetic loci and pathways contributing to the heritability of general cognitive function.

Cigarette smoking and hip volumetric bone mineral density and cortical volume loss in older adults: The AGES-Reykjavik study

This study aimed to explore the relationships of several indicators of cigarette smoking habits (smoking status, pack-years, age at smoking initiation and smoking cessation) with quantitative computed tomographic (QCT)-derived proximal femur bone measures (trabecular vBMD, integral vBMD and the ratio of cortical to total tissue volume (cvol/ivol)) and with subsequent change in these measures over the next five years. A total of 2673 older adults (55.9% women), aged 66-92 years at baseline from the Age, Gene/Environment Susceptibility (AGES)-Reykjavik Study, who had two QCT scans of the hip were studied. In multivariable linear regression models, compared to never-smokers, current smokers had lower cvol/ivol at baseline and former-smokers had poorer measures on all outcomes (lower trabecular vBMD, integral vBMD and cvol/ivol), even when adjusted for several potential confounders. Further, among former smokers, those with higher pack-years had worse bone outcomes and those with longer duration since smoking cessation had better bone health at baseline. Analyses of change in bone measures revealed that compared to never-smokers, current smokers had significantly greater loss of trabecular vBMD, integral vBMD, and cvol/ivol. The regression models included adjustment for sex, age, education, and baseline body mass index, creatinine, % weight change from age 50, 25OHD, physical activity level, high-sensitive C-Reactive protein levels, alcohol and coffee consumption, history of diabetes mellitus, arthritis, and respiratory diseases. In conclusion, both current and former smoking showed adverse associations with bone health assessed with QCT. Results suggest that current smoking in particular may aggravate the rate of bone loss at older age and highlight implications for targeting this risk factor in populations that present higher smoking prevalence and vulnerability to bone fragility.

Cognitive Status, Gray Matter Atrophy, and Lower Orthostatic Blood Pressure in Older Adults

BACKGROUND

Associations between orthostatic blood pressure and cognitive status (CS) have been described with conflicting results.

OBJECTIVE

We hypothesize that long-term exposure to lower orthostatic blood pressure is related to having worse CS later in life and that atrophy of regions involved in central regulation of autonomic function mediate these associations.

METHODS

Three-to-four measures of orthostatic blood pressure were obtained from 1997-2003 in a longitudinal cohort of aging, and average systolic orthostatic blood pressure response (ASOBPR) was computed as % change in systolic blood pressure from sit-to-stand measured at one minute post stand. CS was determined in 2010-2012 by clinician-adjudication (n = 240; age = 87.1±2.6; 59% women; 37% black) with a subsample also undergoing concurrent structural neuroimaging (n = 129). Gray matter volume of regions related to autonomic function was measured. Multinomial regression was used to compare ASOBPR in those who were cognitively intact versus those with a diagnosis of mild cognitive impairment or dementia, controlling for demographics, trajectories of seated blood pressure, incident cardiovascular risk/events and medications measured from 1997 to 2012. Models were repeated in the subsample with neuroimaging, before and after adjustment for regional gray matter volume.

RESULTS

There was an inverse association between ASOBPR and probability of dementia diagnosis (9% lower probability for each % point higher ASOBPR: OR 0.91, CI95%  = 0.85-0.98; p = 0.01). Associations were similar in the subgroup with neuroimaging before and after adjustment for regional gray matter volume.

CONCLUSION

ASOBPR may be an early marker of risk of dementia in older adults living in the community.

Abstract WP169: Midlife to Late-Life Changes in Blood Pressure and Cerebral Blood Flow in Old Age: the AGES-Reykjavik Study

Introduction: Adverse changes in blood pressure (BP) over the life course can lead to adverse cerebrovascular outcomes, including reduced blood flow. In this life-course, longitudinal, population-based study, we investigated the link between midlife to late life changes in BP and cerebral blood flow (CBF) in old age.

Methods: From the Age, Gene/Environment Susceptibility (AGES)–Reykjavik Study (2002-2011), 2491 individuals (mean age (SD): midlife 49.7 (6.1) and late-life 79.8 (4.7) years old) were included. BP was measured at three different time points: 1 in mid-life, and 2 in late-life measured 5 years apart (mean follow-up time 30.1 years). With linear mixed models, annual changes in BP were estimated for each participant (mmHg/year). Participants were categorized in tertiles of changes in systolic, pulse pressure and diastolic BP. Total CBF was measured in the last late-life visit with the Phase-Contrast MRI and standardized for brain parenchymal volume (mL/min/100mL).

Results: Overall, each mmHg/year increase in systolic BP was associated with 3.2 mL/min/100 mL (95% CI: 0.7-5.7)) higher CBF. Mean (SE) CBF in low, middle and high tertiles of change in systolic BP were 56.0 (0.4), 56.6 (0.4) and 57.5 (0.4) mL/min/100mL respectively (P for trend: 0.01). A similar increase in total CBF was observed for an increase in pulse pressure: each mmHg/year increase in pulse pressure was associated with 6.3 mL/min/100mL (95% CI: 3.8-8.7) higher total CBF. In contrast, an increase in diastolic BP was linked with lower CBF: each mmHg/year increase in diastolic BP was associated with 6.3 mL/min/100mL (95% CI: 3.3-9.4) lower CBF. Mean (SE) CBF in low, middle and high tertiles of changes in diastolic BP were 57.3 (0.4), 57.3 (0.4) and 55.5 (0.4) mL/min/100mL respectively (P for trend: <0.001). All these associations were independent of sociodemographic and cardiovascular factors and antihypertensive medications.

Conclusion: In an over 30 years of midlife to late-life follow up, we observed that individuals with increasing systolic BP and pulse pressure have higher CBF in old age. Conversely, increase in diastolic BP is associated with lower CBF. The mechanisms behind the link between long-term BP alterations and CBF need to be elucidated.

Trends in the incidence of dementia: design and methods in the Alzheimer Cohorts Consortium

Several studies have reported a decline in incidence of dementia which may have large implications for the projected burden of disease, and provide important guidance to preventive efforts. However, reports are conflicting or inconclusive with regard to the impact of gender and education with underlying causes of a presumed declining trend remaining largely unidentified. The Alzheimer Cohorts Consortium aggregates data from nine international population-based cohorts to determine changes in the incidence of dementia since 1990. We will employ Poisson regression models to calculate incidence rates in each cohort and Cox proportional hazard regression to compare 5-year cumulative hazards across study-specific epochs. Finally, we will meta-analyse changes per decade across cohorts, and repeat all analysis stratified by sex, education and APOE genotype. In all cohorts combined, there are data on almost 69,000 people at risk of dementia with the range of follow-up years between 2 and 27. The average age at baseline is similar across cohorts ranging between 72 and 77. Uniting a wide range of disease-specific and methodological expertise in research teams, the first analyses within the Alzheimer Cohorts Consortium are underway to tackle outstanding challenges in the assessment of time-trends in dementia occurrence.