Genetic correlations and genome-wide associations of cortical structure in general population samples of 22,824 adults

Cortical thickness, surface area and volumes vary with age and cognitive function, and in neurological and psychiatric diseases. Here we report heritability, genetic correlations and genome-wide associations of these cortical measures across the whole cortex, and in 34 anatomically predefined regions. Our discovery sample comprises 22,824 individuals from 20 cohorts within the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium and the UK Biobank. We identify genetic heterogeneity between cortical measures and brain regions, and 160 genome-wide significant associations pointing to wnt/β-catenin, TGF-β and sonic hedgehog pathways. There is enrichment for genes involved in anthropometric traits, hindbrain development, vascular and neurodegenerative disease and psychiatric conditions. These data are a rich resource for studies of the biological mechanisms behind cortical development and aging.

Cortex morphology varies with age, cognitive function, and in neurological and psychiatric diseases. Here the authors report 160 genome-wide significant associations with thickness, surface area and volume of the total cortex and 34 cortical regions from a GWAS meta-analysis in 22,824 adults.

Growth Differentiation Factor 15 and NT-proBNP as Blood-Based Markers of Vascular Brain Injury and Dementia

Background

GDF15 (growth differentiation factor 15) and NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) may offer promise as biomarkers for cognitive outcomes, including dementia. We determined the association of these biomarkers with cognitive outcomes in a community‐based cohort.

Methods and Results

Plasma GDF15 (n=1603) and NT‐proBNP levels (n=1590) (53% women; mean age, 68.7 years) were measured in dementia‐free Framingham Offspring cohort participants at examination 7 (1998–2001). Participants were followed up for incident dementia. Secondary outcomes included Alzheimer disease dementia, magnetic resonance imaging structural brain measures, and neurocognitive performance. During a median 11.8‐year follow‐up, 131 participants developed dementia. On multivariable Cox proportional‐hazards analysis, higher circulating GDF15 was associated with an increased risk of incident all‐cause and Alzheimer disease dementia (hazard ratio [HR] per SD increment in natural log‐transformed biomarker value, 1.54 [95% CI, 1.22–1.95] and 1.37 [95% CI, 1.03–1.81], respectively), whereas higher plasma NT‐proBNP was also associated with an increased risk of all‐cause dementia (HR, 1.32; 95% CI, 1.05–1.65). Elevated GDF15 was associated with lower total brain and hippocampal volumes, greater white matter hyperintensity volume, and poorer cognitive performance. Elevated NT‐proBNP was associated with greater white matter hyperintensity volume and poorer cognitive performance. Addition of both biomarkers to a conventional risk factor model improved dementia risk classification (net reclassification improvement index, 0.25; 95% CI, 0.05–0.45).

Conclusions

Elevated plasma GDF15 and NT‐proBNP were associated with vascular brain injury on magnetic resonance imaging, poorer neurocognitive performance, and increased risk of incident dementia in individuals aged >60 years. Both biomarkers improved dementia risk classification beyond that of traditional clinical risk factors, indicating their potential value in predicting incident dementia.

Relation of plasma β-amyloid, clusterin, and tau with cerebral microbleeds: Framingham Heart Study

OBJECTIVE

Cerebral microbleeds (CMBs) are associated with higher risk of stroke and dementia, predating clinical diagnosis by several years. CMB are considered markers of cerebral small vessel disease (CSVD): hypertensive (deep CMB) and cerebral amyloid angiopathy (lobar CMB). We related plasma β-Amyloid (40, 42 and their ratio), clusterin, and tau levels to CMB to elucidate their role as biomarkers for the angiopathies represented by CMB.

METHODS

Dementia, stroke, and other neurological disease-free Framingham Heart Study participants with available CMB and biomarker measurements were included. We related biomarker levels (standardized for analyses) to CMB presence overall and stratified by brain topography (any, lobar, deep), using multivariable logistic regression analyses.

RESULTS

CMB were observed in 208 (5.7%) participants (mean age 57 years, 54% women). After multivariable adjustment, Aβ1-40 was associated with any CMB (OR (95%CI) 1.20 (0.99, 1.45) P = 0.062)) and lobar CMB (OR (95%CI) 1.33 (1.05, 1.68) P = 0.019), but not with deep CMB. Log-Aβ1-42 levels were not associated with CMB overall. Clusterin was related to mixed CMB (1.70 [1.05, 2.74], P = 0.031). Tau levels were associated with any CMB (OR (95%CI) 1.26 (1.07, 1.49) P = 0.006), lobar CMB (OR (95%CI) 1.26 (1.05, 1.52) P = 0.013), and with deep CMB (OR (95% CI) 1.46 (1.13, 1.89) P = 0.004).

INTERPRETATION

We found that plasma Aβ1-40 and Tau are associated with CMB but further studies are needed to confirm their role in hemorrhage prone CSVD represented by CMB and as indicators of ongoing subclinical neuronal injury.

Methionine Sulfoxide Reductase-B3 Risk Allele Implicated in Alzheimer's Disease Associates with Increased Odds for Brain Infarcts

Genome-wide association studies identified a single nucleotide polymorphism (SNP) in the MSRB3 gene encoding Methionine Sulfoxide Reductase-B3 (MsrB3) to be associated with the risk for low hippocampal volume and late onset Alzheimer's disease (AD). Subsequently, we identified AD-associated abnormal patterns of neuronal and vascular MsrB3 expression in postmortem hippocampi. The present study investigated the relationship between the MSRB3 SNP rs61921502, G (minor/risk allele) and MRI measures of brain injury including total brain volume, hippocampal volume, and white matter hyperintensities using linear regression models; the presence of brain infarcts using logistic regression models; and the incidence of stroke, dementia, and AD using Cox proportional hazards models in 2,038 Framingham Heart Study Offspring participants with MRI administered close to examination cycle 7 (1998-2001). Participants with neurological conditions that impede evaluation of vascular pathology by MRI, i.e., brain tumors, multiple sclerosis, and major head trauma, were excluded from the study. When adjusted for age and age squared at MRI exam, sex, and presence of Apolipoproteinɛ4 allele (APOE4), individuals with MSRB3 rs61921502 minor allele had increased odds for brain infarcts on MRI compared to those with no minor allele. However, in stratified analyses, MSRB3 rs61921502 minor allele was significantly associated with increased odds for MRI brain infarcts only in the absence of APOE4.

0419 IL-6 Moderates the Association Between Obstructive Sleep Apnea Severity and Incident Alzheimer’s Disease: The Framingham Heart Study

Introduction

Both sleep disturbances and inflammation are potential risk factors for Alzheimer’s disease (AD). However, it is unknown how inflammation and sleep interact together to influence the risk of developing AD dementia. Our objective was to evaluate whether interleukin-6 (IL-6) levels interact with sleep disturbances when predicting incident clinical AD.

Methods

We studied participants in the Framingham Heart Study Offspring cohort who completed in-home overnight polysomnography. Sleep characteristics were continuous and included sleep duration, wake after sleep onset (WASO), and apnea-hypopnea index (AHI). Participants were stratified into quartiles of IL-6 levels. Surveillance for incident AD dementia occurred over a mean follow-up of 13.4±5.4 years. Using Cox proportional hazards regression models, we tested the interaction of sleep measures by IL-6 quartiles on incident AD dementia. All analyses adjusted for age and sex and P<0.05 was considered significant.

Results

The final sample included 291 dementia-free participants at baseline (age 67.5±4.9 years, 51.6% men). Approximately one quarter of participants had obstructive sleep apnea (OSA; AHI>15) at baseline (median:6.2, Q1:2,3, Q3:14.3). We observed 33 cases of incident AD dementia during follow-up. Although no interaction was observed for either sleep duration or WASO with IL-6 levels, there was a significant interaction of AHI with IL-6 in predicting AD dementia (p=0.002). In the lowest IL-6 quartile, higher AHI was associated with an elevated risk of AD dementia (hazard ratio, 4.15 [95%CI, 1.42, 12.1], p=0.01) whereas no association between AHI and incident AD was observed in other IL-6 quartiles.

Conclusion

Our findings suggest that the pro-inflammatory cytokine IL-6 moderates the association between OSA and incident AD risk. The association between increasing OSA severity and incident AD was only observed in those with lower IL-6 levels, suggesting that this association might be especially apparent when no other confounding risk factors such as inflammation are present.

Support

The Framingham Heart Study is supported by contracts from the National Heart, Lung and Blood Institute, grants from the National Institute on Aging, and grants from the National Institute of Neurological Disorders and Stroke.

The progression of carotid atherosclerosis and imaging markers of dementia

INTRODUCTION

We studied the association of carotid intima-media thickness (CIMT) with hippocampal volume (HV) in community dwelling individuals, testing the hypothesis that persons with carotid atherosclerosis progression would have lower HV.

METHODS

We studied 1376 Framingham Offspring participants with two carotid ultrasounds and brain magnetic resonance imaging (MRIs). We used multivariable linear regression analyses to relate CIMT progression and HV and total brain volume. Regression models were adjusted for demographics and vascular risk factors, time interval between imaging examinations, and baseline CIMT. We assessed effect modification by hypertension treatment (HRx).

RESULTS

Participants with higher ICA IMT progression had significantly lower HV after adjustment for vascular risk factors and baseline IMT (standardized beta ± standard error: -0.067 ± 0.027, P = .01). We observed weaker association between ICA IMT change and HV among subjects treated for hypertension (β = -0.047, P = .19 vs β = -0.096, P = .026).

DISCUSSION

Cumulative vascular risk factor exposure, reflected by CIMT progression, may increase the risk of neurodegeneration.

Assessment of Plasma Total Tau Level as a Predictive Biomarker for Dementia and Related Endophenotypes

Importance

Blood-based biomarkers have the potential to improve the identification of persons with the greatest dementia risk for inclusion in dementia prevention trials through low-cost and minimally invasive screening.

Objective

To investigate the use of plasma total tau as a blood biomarker for dementia and related endophenotypes.

Design, Setting, and Participants

This prospective cohort study used data from the US community-based Framingham Heart Study with replication in the Memento study, a multicenter cohort of persons with mild cognitive impairment or subjective cognitive complaints recruited from memory clinics across France. Total tau levels were measured from stored plasma samples in Framingham Heart Study participants during 2004 to 2011. Dementia follow-up occurred across a median of 6 years (interquartile range, 5-8 years) for persons 65 years and older who were dementia free at baseline. Plasma and/or cerebrospinal fluid samples were obtained from Memento study participants from April 19, 2011, to June 22, 2016. Dementia follow-up took place over a median of 4 years (interquartile range, 3-5 years). Data analysis was performed from January to November 2018.

Exposures

Plasma total tau level measured using single-molecule array technology.

Main Outcomes and Measures

Incidence of dementia of any cause (all dementia) and dementia due to clinical Alzheimer disease (AD dementia).

Results

Among the 1453 participants in the Framingham dementia study sample, the mean (SD) age was 75 (7) years; 792 (54.5%) were female. Among the 367 individuals in the replication cohort, the mean (SD) age was 69 (9) years; 217 (59.1%) were female. Of 134 cases of incident all dementia in the Framingham sample, 105 were AD dementia. After adjustment for age and sex, each SD unit increase in the log of plasma total tau level was associated with a 35% increase in AD dementia risk (hazard ratio [HR], 1.35; 95% CI, 1.10-1.67). The addition of plasma total tau to a model including age and sex improved the stratification of participants for risk of AD dementia (net reclassification improvement, 0.382; 95% CI, 0.030-0.716). Higher plasma total tau level was associated with poorer cognition across 7 cognitive tasks (P < .05) and smaller hippocampi (hippocampal volume: β [SE] = 0.002 [0.001]; P = .003) as well as neurofibrillary tangles (β [SE] = 0.95 [0.45]; P = .04) and microinfarcts (odds ratio, 3.04; 95% CI, 1.26-7.37) at autopsy. In the replication cohort, plasma total tau level weakly correlated with cerebrospinal fluid total tau level (Spearman correlation coefficient, 0.16; P = .07), but plasma total tau was at least as strongly associated with incident AD dementia as cerebrospinal fluid total tau (log plasma total tau: HR, 2.33; 95% CI, 1.00-5.48; log cerebrospinal fluid total tau: HR, 2.14; 95% CI, 1.33-3.44) after adjustment for age and sex.

Conclusions and Relevance

The findings suggest that plasma total tau levels may improve the prediction of future dementia, are associated with dementia endophenotypes, and may be used as a biomarker for risk stratification in dementia prevention trials.

Association of CD14 with incident dementia and markers of brain aging and injury

OBJECTIVE

To test the hypothesis that the inflammatory marker plasma soluble CD14 (sCD14) associates with incident dementia and related endophenotypes in 2 community-based cohorts.

METHODS

Our samples included the prospective community-based Framingham Heart Study (FHS) and Cardiovascular Health Study (CHS) cohorts. Plasma sCD14 was measured at baseline and related to the incidence of dementia, domains of cognitive function, and MRI-defined brain volumes. Follow-up for dementia occurred over a mean of 10 years (SD 4) in the FHS and a mean of 6 years (SD 3) in the CHS.

RESULTS

We studied 1,588 participants from the FHS (mean age 69 ± 6 years, 47% male, 131 incident events) and 3,129 participants from the CHS (mean age 72 ± 5 years, 41% male, 724 incident events) for the risk of incident dementia. Meta-analysis across the 2 cohorts showed that each SD unit increase in sCD14 was associated with a 12% increase in the risk of incident dementia (95% confidence interval 1.03-1.23; p = 0.01) following adjustments for age, sex, APOE ε4 status, and vascular risk factors. Higher levels of sCD14 were associated with various cognitive and MRI markers of accelerated brain aging in both cohorts and with a greater progression of brain atrophy and a decline in executive function in the FHS.

CONCLUSION

sCD14 is an inflammatory marker related to brain atrophy, cognitive decline, and incident dementia.

Circulating ceramide ratios and risk of vascular brain aging and dementia

Background

We determined the association between ratios of plasma ceramide species of differing fatty‐acyl chain lengths and incident dementia and Alzheimer’s disease (AD) dementia in a large, community‐based sample.

Methods

We measured plasma ceramide levels in 1892 [54% women, mean age 70.1 (SD 6.9) yr.] dementia‐free Framingham Offspring Study cohort participants between 2005 and 2008. We related ratios of very long‐chain (C24:0, C22:0) to long‐chain (C16:0) ceramides to subsequent risk of incident dementia and AD dementia. Structural MRI brain measures were included as secondary outcomes.

Results

During a median 6.5 year follow‐up, 81 participants developed dementia, of whom 60 were diagnosed with AD dementia. In multivariable Cox‐proportional hazards analyses, each standard deviation (SD) increment in the ratio of ceramides C24:0/C16:0 was associated with a 27% reduction in the risk of dementia (HR 0.73, 95% CI 0.56–0.96) and AD dementia (HR 0.73, 95% CI 0.53–1.00). The ratio of ceramides C22:0/C16:0 was also inversely associated with incident dementia (HR per SD 0.75, 95% CI 0.57–0.98), and approached statistical significance for AD (HR 0.73, 95% CI 0.53–1.01, P = 0.056). Higher ratios of ceramides C24:0/C16:0 and C22:0/C16:0 were also cross‐sectionally associated with lower white matter hyperintensity burden on MRI (−0.05 ± 0.02, P = 0.02; −0.06 ± 0.02, P = 0.003; respectively per SD increase), but not with other MRI brain measures.

Conclusions

Higher plasma ratios of very long‐chain to long‐chain ceramides are associated with a reduced risk of incident dementia and AD dementia in our community‐based sample. Circulating ceramide ratios may serve as potential biomarkers for predicting dementia risk in cognitively healthy adults.

Antihypertensive medications and risk for incident dementia and Alzheimer's disease: a meta-analysis of individual participant data from prospective cohort studies

BACKGROUND

Dementia is a major health concern for which prevention and treatment strategies remain elusive. Lowering high blood pressure with specific antihypertensive medications (AHMs) could reduce the burden of disease. We investigated whether specific AHM classes reduced the risk for dementia.

METHODS

We did a meta-analysis of individual participant data from eligible observational studies published between Jan 1, 1980, and Jan 1, 2019. Cohorts were eligible for inclusion if they prospectively recruited community-dwelling adults; included more than 2000 participants; collected data for dementia events over at least 5 years; had measured blood pressure and verified use of AHMs; included in-person exams, supplemented with additional data, to capture dementia events; and had followed up cases for mortality. We assessed the association of incident dementia and clinical Alzheimer's disease with use of five AHM classes, within strata of baseline high (systolic blood pressure [SBP] ≥140 mm Hg or diastolic blood pressure [DBP] ≥90 mm Hg) and normal (SBP <140 mm Hg and DBP <90 mm Hg) blood pressure. We used a propensity score to control for confounding factors related to the probability of receiving AHM. Study-specific effect estimates were pooled using random-effects meta-analyses.

RESULTS

Six prospective community-based studies (n=31 090 well phenotyped dementia-free adults older than 55 years) with median follow-ups across cohorts of 7-22 years were eligible for analysis. There were 3728 incident cases of dementia and 1741 incident Alzheimer's disease diagnoses. In the high blood pressure stratum (n=15 537), those using any AHM had a reduced risk for developing dementia (hazard ratio [HR] 0·88, 95% CI 0·79-0·98; p=0·019) and Alzheimer's disease (HR 0·84, 0·73-0·97; p=0·021) compared with those not using AHM. We did not find any significant differences between one drug class versus all others on risk of dementia. In the normal blood pressure stratum (n=15 553), there was no association between AHM use and incident dementia or Alzheimer's disease.

INTERPRETATION

Over a long period of observation, no evidence was found that a specific AHM drug class was more effective than others in lowering risk of dementia. Among people with hypertensive levels of blood pressure, use of any AHM with efficacy to lower blood pressure might reduce the risk for dementia. These findings suggest future clinical guidelines for hypertension management should also consider the beneficial effect of AHM on the risk for dementia.

FUNDING

The Alzheimer's Drug Discovery Foundation and the National Institute on Aging Intramural Research Program.

Mid-life and late-life vascular risk factor burden and neuropathology in old age

OBJECTIVE

To determine whether vascular risk factor burden in mid- or late-life associates with postmortem vascular and neurodegenerative pathologies in a community-based sample.

METHODS

We studied participants from the Framingham Heart Study who participated in our voluntary brain bank program. Overall vascular risk factor burden was calculated using the Framingham Stroke Risk Profile (FSRP). Mid-life FSRP was measured at 50 to 60 years of age. Following death, brains were autopsied and semi-quantitatively assessed by board-certified neuropathologists for cerebrovascular outcomes (cortical infarcts, subcortical infarcts, atherosclerosis, arteriosclerosis) and Alzheimer's disease pathology (Braak stage, cerebral amyloid angiopathy, and neuritic plaque score). We estimated adjusted odds ratios between vascular risk burden (at mid-life and before death) and neuropathological outcomes using logistic and proportional-odds logistic models.

RESULTS

The median time interval between FSRP and death was 33.4 years for mid-life FSRP and 4.4 years for final FSRP measurement before death. Higher mid-life vascular risk burden was associated with increased odds of all cerebrovascular pathology, even with adjustment for vascular risk burden before death. Late-life vascular risk burden was associated with increased odds of cortical infarcts (OR [95% CI]: 1.04 [1.00, 1.08]) and arteriosclerosis stage (OR [95% CI]: 1.03 [1.00, 1.05]). Mid-life vascular risk burden was not associated with Alzheimer's disease pathology, though late-life vascular risk burden was associated with increased odds of higher Braak stage (OR [95% CI]: 1.03 [1.01, 1.05]).

INTERPRETATION

Mid-life vascular risk burden was predictive of cerebrovascular but not Alzheimer's disease neuropathology, even after adjustment for vascular risk factors before death.

Genetic architecture of subcortical brain structures in 38,851 individuals

Subcortical brain structures are integral to motion, consciousness, emotions and learning. We identified common genetic variation related to the volumes of the nucleus accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen and thalamus, using genome-wide association analyses in almost 40,000 individuals from CHARGE, ENIGMA and UK Biobank. We show that variability in subcortical volumes is heritable, and identify 48 significantly associated loci (40 novel at the time of analysis). Annotation of these loci by utilizing gene expression, methylation and neuropathological data identified 199 genes putatively implicated in neurodevelopment, synaptic signaling, axonal transport, apoptosis, inflammation/infection and susceptibility to neurological disorders. This set of genes is significantly enriched for Drosophila orthologs associated with neurodevelopmental phenotypes, suggesting evolutionarily conserved mechanisms. Our findings uncover novel biology and potential drug targets underlying brain development and disease.

Accelerometer-determined physical activity and cognitive function in middle-aged and older adults from two generations of the Framingham Heart Study

INTRODUCTION

Physical activity (PA) may play a role in maintenance of cognitive function in both middle and older ages and prevention of outcomes such as dementia and Alzheimer's disease.

METHODS

Cross-sectional regression analyses were performed in Framingham Heart Study Third Generation (n = 1861) and Offspring (n = 909) cohort participants assessing the association of accelerometry-measured PA with cognitive function, adjusting for age, sex, accelerometer wear time, education, occupational status/PA, and smoking status.

RESULTS

In each cohort, achieving just 10-21.4 min/day moderate-to-vigorous PA related to better executive function (P < .02); and just 10 min/day moderate-to-vigorous PA was associated with better verbal memory in middle-aged adults in the Third Generation cohort (P = .02). In older adults of the Offspring cohort, total PA (measured in steps/day) was associated with better executive function (P < .02).

DISCUSSION

PA at levels lower than the current PA Guidelines (just 10 min/day moderate-to-vigorous PA and total PA including lower intensity PA) were associated with better cognitive function.

Non-alcoholic fatty liver disease, liver fibrosis score and cognitive function in middle-aged adults: The Framingham Study

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is common and has been recently related to brain health. We aimed to assess the relationships of NAFLD and its severity, using the NAFLD fibrosis score (NFS), with cognitive performance.

METHODS

Framingham study Offspring and 3rd generation participants were included if they attended exams 9 (2002-2008) and 2 (2008-2011), respectively, were free of dementia and stroke, and did not have excessive alcohol intake. Between 2008 and 2011, participants underwent Multi-detector computed tomography scans of the abdomen to determine NAFLD diagnosis and the NFS was used to categorize the severity of fibrosis. Cross-sectional relationships of NAFLD and the NFS with cognitive testing of memory, abstract reasoning, visual perception, attention and executive function were assessed, while adjusting for multiple cardiometabolic variables including visceral adipose tissue, diabetes and insulin resistance.

RESULTS

Of the 1287 participants (mean age = 61±12 years, 48% men), 378 (29%) had NAFLD. The presence of NAFLD was not associated with cognitive function. However, among those with NAFLD (mean age = 61±12 years; 58% men), high compared to low risk of advanced fibrosis was associated with poorer performance on similarities (β = -2.22 ± 0.83; P = 0.009) and trail-making B minus A (β = -0.11 ± 0.05; P = 0.028), independently of potential confounders.

CONCLUSIONS

Participants with high risk of advanced fibrosis may have poorer cognitive function compared to those with low risk, particularly in executive function and abstract reasoning. Future findings are necessary to evaluate the value of the NFS as a biomarker that predicts cognitive impairment and dementia and to explore the role of hepatic fibrosis in brain health.

Plasma total-tau as a biomarker of stroke risk in the community

Higher plasma total-tau level is associated with incident dementia, but its relationship with stroke risk is unknown. In this prospective community-based study, we evaluated plasma total-tau level as a biomarker of stroke risk in 2,794 Framingham Heart Study participants. Persons with plasma total-tau levels in the top quintile, versus the bottom 4, had an increased risk of incident stroke over a mean follow-up of 8.3 years (hazard ratio = 2.01; 95% confidence interval = 1.32-3.08) following adjustments for age, sex, and stroke risk factors. Our findings demonstrate that plasma total-tau relates to the risk of stroke in a community sample. ANN NEUROL 2019;86:463-467.

Circulating IGFBP-2: a novel biomarker for incident dementia

OBJECTIVE

To determine the association between plasma insulin-like growth factor binding protein 2 (IGFBP-2) and cognitive outcomes.

METHODS

We measured plasma IGFBP-2 levels in 1596 (53% women, mean age 68.7 [SD 5.7] years) dementia-free Framingham Offspring cohort participants between 1998 and 2001. Multivariable Cox proportional hazards models related plasma IGFBP-2 to subsequent risk of incident dementia and Alzheimer's disease. MRI brain measures and cognitive performance were included as secondary outcomes.

RESULTS

During a median follow-up of 11.8 (Q1, Q3: 7.1, 13.3) years, 131 participants developed incident dementia, of whom 98 were diagnosed with Alzheimer's disease. The highest tertile of IGFBP-2, compared to the lowest tertile, was associated with an increased risk of incident all-cause dementia (hazard ratio [HR] 2.89, 95% CI 1.63-5.13) and Alzheimer's disease (HR 3.63, 95% CI 1.76-7.50) in multivariable analysis. Higher circulating IGFBP2 levels were also cross-sectionally associated with poorer performance on tests of abstract reasoning but not with MRI-based outcomes. After adding plasma IGFBP-2 levels to a conventional dementia prediction model, 32% of individuals with dementia were correctly assigned a higher predicted risk, while 8% of individuals without dementia were correctly assigned a lower predicted risk (overall net reclassification improvement index, 0.40, 95% CI 0.22-0.59).

INTERPRETATION

Elevated circulating IGFBP-2 levels were associated with an increased risk of both all-cause dementia and Alzheimer's disease. Addition of IGFBP2 plasma levels to a model of traditional risk factors significantly improved dementia risk classification. Manipulation of insulin-like growth factor signaling via IGFBP-2 may be a promising therapeutic target for dementia.

Whole blood microRNA expression associated with stroke: Results from the Framingham Heart Study

Emerging evidence suggests microRNAs (miRNAs) may play an important role in explaining variation in stroke risk and recovery in humans, yet there are still few longitudinal studies examining the association between whole blood miRNAs and stroke. Accounting for multiple testing and adjusting for potentially confounding technical and clinical variables, here we show that whole blood miR-574-3p expression was significantly lower in participants with chronic stroke compared to non-cases. To explore the functional relevance of our findings, we analyzed miRNA-mRNA whole blood co-expression, pathway enrichment, and brain tissue gene expression. Results suggest miR-574-3p is involved in neurometabolic and chronic neuronal injury response pathways, including brain gene expression of DBNDD2 and ELOVL1. These results suggest miR-574-3p plays a role in regulating chronic brain and systemic cellular response to stroke and thus may implicate miR-574-3p as a partial mediator of long-term stroke outcomes.

Temporal Trends in Ischemic Stroke Incidence in Younger Adults in the Framingham Study

Background and Purpose- Stroke at midlife has a disproportionately large impact on disability-adjusted life-years lost. Ischemic stroke incidence may be increasing at this age. We investigated long-term trends in ischemic stroke incidence and changes in stroke risk factors in a community sample stratified by stroke onset at middle and older age. Methods- In the Framingham Study, surveillance for incident stroke is ongoing since 1948. We examined age-adjusted and sex-adjusted 10-year incidence of ischemic stroke using Cox models in persons aged 35 to 54 and ≥55 years at start of follow-up. Tests for linear trend were performed over 4 epochs, controlling for the distance in time between intervals. Further, we calculated the mean 10-year risk of stroke at each epoch and for both age groups, based on vascular risk factors from the Framingham Stroke Risk Profile. Results- There were 153, 197, 176, and 165 incident ischemic strokes within each epoch beginning in 1962 (n=3966), 1971 (n=5779), 1987 (n=5133), and 1998 (n=6964). Most ischemic strokes at midlife (n=71) were because of atherosclerotic brain infarction (n=50) or cardioembolism (n=19). Using the risk in the 1962 epoch as the reference, the risk of ischemic stroke at midlife did not significantly decline (hazard ratio, 0.87; 95% CI, 0.74-1.02; P trend =0.09). Incidence of ischemic stroke declined in the older group (hazard ratio, 0.82; 95% CI, 0.77-0.88; P trend <0.001). Between epochs 1 and 4, the average 10-year risk of stroke, as estimated by the Framingham Stroke Risk Profile, declined by 0.7% at midlife and 1.1% at older age. Conclusions- Long-term rates of ischemic stroke declined in our community sample; the decline was greater in older as compared with younger adults. Early prevention, focused on modification of cardiovascular risk factors, is important to see sustained declines in stroke incidence and mortality at midlife.