The Framingham Brain Donation Program: neuropathology along the cognitive continuum

Subjective Cognitive Decline Plus and Longitudinal Assessment and Risk for Cognitive Impairment

Importance

Subjective cognitive decline (SCD) is recognized to be in the Alzheimer disease (AD) cognitive continuum. The SCD Initiative International Working Group recently proposed SCD-plus (SCD+) features that increase risk for future objective cognitive decline but that have not been assessed in a large community-based setting.

Objective

To assess SCD risk for mild cognitive impairment (MCI), AD, and all-cause dementia, using SCD+ criteria among cognitively normal adults.

Design, Setting, and Participants

The Framingham Heart Study, a community-based prospective cohort study, assessed SCD between 2005 and 2019, with up to 12 years of follow-up. Participants 60 years and older with normal cognition at analytic baseline were included. Cox proportional hazards (CPH) models were adjusted for baseline age, sex, education, APOE ε4 status, and tertiles of AD polygenic risk score (PRS), excluding the APOE region. Data were analyzed from May 2021 to November 2023.

Exposure

SCD was assessed longitudinally using a single question and considered present if endorsed at the last cognitively normal visit. It was treated as a time-varying variable, beginning at the first of consecutive, cognitively normal visits, including the last, at which it was endorsed.

Main Outcomes and Measures

Consensus-diagnosed MCI, AD, and all-cause dementia.

Results

This study included 3585 participants (mean [SD] baseline age, 68.0 [7.7] years; 1975 female [55.1%]). A total of 1596 participants (44.5%) had SCD, and 770 (21.5%) were carriers of APOE ε4. APOE ε4 and tertiles of AD PRS status did not significantly differ between the SCD and non-SCD groups. MCI, AD, and all-cause dementia were diagnosed in 236 participants (6.6%), 73 participants (2.0%), and 89 participants (2.5%), respectively, during follow-up. On average, SCD preceded MCI by 4.4 years, AD by 6.8 years, and all-cause dementia by 6.9 years. SCD was significantly associated with survival time to MCI (hazard ratio [HR], 1.57; 95% CI, 1.22-2.03; P <.001), AD (HR, 2.98; 95% CI, 1.89-4.70; P <.001), and all-cause dementia (HR, 2.14; 95% CI, 1.44-3.18; P <.001). After adjustment for APOE and AD PRS, the hazards of SCD were largely unchanged.

Conclusions and Relevance

Results of this cohort study suggest that in a community setting, SCD reflecting SCD+ features was associated with an increased risk of future MCI, AD, and all-cause dementia with similar hazards estimated in clinic-based settings. SCD may be an independent risk factor for AD and other dementias beyond the risk incurred by APOE ε4 and AD PRS.

Lack of Association of Informant-Reported Traumatic Brain Injury and Chronic Traumatic Encephalopathy

Repetitive head impacts (RHIs) from football are associated with the neurodegenerative tauopathy chronic traumatic encephalopathy (CTE). It is unclear whether a history of traumatic brain injury (TBI) is sufficient to precipitate CTE neuropathology. We examined the association between TBI and CTE neuropathology in 580 deceased individuals exposed to RHIs from football. TBI history was assessed using a modified version of the Ohio State University TBI Identification Method Short Form administered to informants. There were 22 donors who had no TBI, 213 who had at least one TBI without loss of consciousness (LOC), 345 who had TBI with LOC, and, of those with a history of TBI with LOC, 36 who had at least one moderate-to-severe TBI (msTBI, LOC >30 min). CTE neuropathology was diagnosed in 405. There was no association between CTE neuropathology status or severity and TBI with LOC (odds ratio [OR] = 0.95, 95% confidence interval [CI] = 0.64-1.41; OR = 1.22, 95% CI = 0.71-2.09) or msTBI (OR = 0.70, 95% CI = 0.33-1.50; OR = 1.01, 95% CI = 0.30-3.41). There were no associations with other neurodegenerative or cerebrovascular pathologies examined. TBI with LOC and msTBI were not associated with CTE neuropathology in this sample of brain donors exposed to RHIs from American football.

Maximizing utility of neuropsychological measures in sex-specific predictive models of incident Alzheimer's disease in the Framingham Heart Study

INTRODUCTION

Sex differences in neuropsychological (NP) test performance might have important implications for the diagnosis of Alzheimer's disease (AD). This study investigates sex differences in neuropsychological performance among individuals without dementia at baseline.

METHODS

Neuropsychological assessment data, both standard test scores and process coded responses, from Framingham Heart Study participants were analyzed for sex differences using regression model and Cox proportional hazards model. Optimal NP profiles were identified by machine learning methods for men and women.

RESULTS

Sex differences were observed in both summary scores and composite process scores of NP tests in terms of adjusted means and their associations with AD incidence. The optimal NP profiles for men and women have 10 and 8 measures, respectively, and achieve 0.76 mean area under the curve for AD prediction.

DISCUSSION

These results suggest that NP tests can be leveraged for developing more sensitive, sex-specific indices for the diagnosis of AD.

The impact of blood MCP-1 levels on Alzheimer's disease with genetic variation of UNC5C and NAV3 loci

Background

Previous study shows that monocyte chemoattractant protein-1 (MCP-1), which is implicated in the peripheral proinflammatory cascade and blood-brain barrier (BBB) disruption, modulates the genetic risks of AD in established AD loci.

Methods

In this study, we hypothesized that blood MCP-1 impacts the AD risk of genetic variants beyond known AD loci. We thus performed a genome-wide association study (GWAS) using the logistic regression via generalized estimating equations (GEE) and the Cox proportional-hazards models to examine the interactive effects between single nucleotide polymorphisms (SNPs) and blood MCP-1 level on AD in three cohorts: the Framingham Heart Study (FHS), Alzheimer's Disease Neuroimaging Initiative (ADNI) and Religious Orders Study/Memory and Aging Project (ROSMAP).

Results

We identified SNPs in two genes, neuron navigator 3 (NAV3, also named Unc-53 Homolog 3, rs696468) (p < 7.55×10- 9) and Unc-5 Netrin Receptor C (UNC5C rs72659964) (p < 1.07×10- 8) that showed an association between increasing levels of blood MCP-1 and AD. Elevating blood MCP-1 concentrations increased AD risk and AD pathology in genotypes of NAV3 (rs696468-CC) and UNC5C (rs72659964-AT + TT), but did not influence the other counterpart genotypes of these variants.

Conclusions

NAV3 and UNC5C are homologs and may increase AD risk through dysregulating the functions of neurite outgrowth and guidance. Overall, the association of risk alleles of NAV3 and UNC5C with AD is enhanced by peripheral MCP-1 level, suggesting that lowering the level of blood MCP-1 may reduce the risk of developing AD for people with these genotypes.

The Potential of Social Policies in Preventing Dementia: An Ecological Study Using Systematic Review and Meta-Analysis

Social policies determine the distribution of factors (e.g. education, cardiovascular health) protecting against the development of dementia in Alzheimer's disease (AD). However, the association between social policies and the likelihood of AD without dementia (ADw/oD) has yet to be evaluated. We estimated this association in an ecological study using systematic review and meta-analysis. Four reference databases were consulted; 18 studies were included in the final analysis. ADw/oD was defined as death without dementia in people with clinically significant AD brain pathology. The indicators of social policy were extracted from the Organisation for Economic Co-operation and Development database (OECD). The probability of ADw/oD with moderate AD brain pathology was inversely associated with the Gini index for disposable income, poverty rate, and certain public expenditures on healthcare. ADw/oD with advanced AD brain pathology was only associated with public expenditures for long-term care. Social policies may play a role in maintaining and sustaining cognitive health among older people with AD.

Longitudinal change in serial position scores in older adults with entorhinal and hippocampal neuropathologies

OBJECTIVE

Serial position scores on verbal memory tests are sensitive to early Alzheimer's disease (AD)-related neuropathological changes that occur in the entorhinal cortex and hippocampus. The current study examines longitudinal change in serial position scores as markers of subtle cognitive decline in older adults who may be in preclinical or at-risk states for AD.

METHODS

This study uses longitudinal data from the Religious Orders Study and the Rush Memory and Aging Project. Participants (n = 141) were included if they did not have dementia at enrollment, completed follow-up assessments, and died and were classified as Braak stage I or II. Memory tests were used to calculate serial position (primacy, recency), total recall, and episodic memory composite scores. A neuropathological evaluation quantified AD, vascular, and Lewy body pathologies. Mixed effects models were used to examine change in memory scores. Neuropathologies and covariates (age, sex, education, APOE e4) were examined as moderators.

RESULTS

Primacy scores declined (β = -.032, p < .001), whereas recency scores increased (β = .021, p = .012). No change was observed in standard memory measures. Greater neurofibrillary tangle density and atherosclerosis explained 10.4% of the variance in primacy decline. Neuropathologies were not associated with recency change.

CONCLUSIONS

In older adults with hippocampal neuropathologies, primacy score decline may be a sensitive marker of early AD-related changes. Tangle density and atherosclerosis had additive effects on decline. Recency improvement may reflect a compensatory mechanism. Monitoring for changes in serial position scores may be a useful in vivo method of tracking incipient AD.

Leveraging football accelerometer data to quantify associations between repetitive head impacts and chronic traumatic encephalopathy in males

Chronic traumatic encephalopathy (CTE) is a neurodegenerative tauopathy associated with repetitive head impacts (RHI), but the components of RHI exposure underlying this relationship are unclear. We create a position exposure matrix (PEM), composed of American football helmet sensor data, summarized from literature review by player position and level of play. Using this PEM, we estimate measures of lifetime RHI exposure for a separate cohort of 631 football playing brain donors. Separate models examine the relationship between CTE pathology and players' concussion count, athletic positions, years of football, and PEM-derived measures, including estimated cumulative head impacts, linear accelerations, and rotational accelerations. Only duration of play and PEM-derived measures are significantly associated with CTE pathology. Models incorporating cumulative linear or rotational acceleration have better model fit and are better predictors of CTE pathology than duration of play or cumulative head impacts alone. These findings implicate cumulative head impact intensity in CTE pathogenesis.

Blood levels of MCP-1 modulate the genetic risks of Alzheimer's disease mediated by HLA-DRB1 and APOE for Alzheimer's disease

INTRODUCTION

C-Reactive protein (CRP) and monocyte chemoattractant protein-1 (MCP-1) are both implicated in the peripheral proinflammatory cascade and blood-brain barrier (BBB) disruption. Since the blood CRP level increases Alzheimer's disease (AD) risk depending on the apolipoprotein E (APOE) genotype, we hypothesized that the blood MCP-1 level exerts different effects on the AD risk depending on the genotypes.

METHODS

Using multiple regression analyses, data from the Framingham Heart Study (n = 2884) and Alzheimer's Disease Neuroimaging Initiative study (n = 231) were analyzed.

RESULTS

An elevated blood MCP-1 level was associated with AD risk in major histocompatibility complex, Class II, DR beta 1 (HLA-DRB1) rs9271192-AC/CC (hazard ratio [HR] = 3.07, 95% confidence interval [CI] = 1.50-6.28, p = 0.002) and in APOE ε4 carriers (HR = 3.22, 95% CI = 1.59-6.53, p = 0.001). In contrast, among HLA-DRB1 rs9271192-AA and APOE ε4 noncarriers, blood MCP-1 levels were not associated with these phenotypes.

DISCUSSION

Since HLA-DRB1 and APOE are expressed in the BBB, blood MCP-1 released in the peripheral inflammatory cascade may function as a mediator of the effects of HLA-DRB1 rs9271192-AC/CC and APOE ε4 genotypes on AD pathogenesis in the brain via the BBB pathways.

Decreased myelin proteins in brain donors exposed to football-related repetitive head impacts

American football players and other individuals exposed to repetitive head impacts can exhibit a constellation of later-life cognitive and neuropsychiatric symptoms. While tau-based diseases such as chronic traumatic encephalopathy can underpin certain symptoms, contributions from non-tau pathologies from repetitive head impacts are increasingly recognized. We examined cross-sectional associations between myelin integrity using immunoassays for myelin-associated glycoprotein and proteolipid protein 1 with risk factors and clinical outcomes in brain donors exposed to repetitive head impacts from American football. Immunoassays for myelin-associated glycoprotein and proteolipid protein 1 were conducted on dorsolateral frontal white matter tissue samples of 205 male brain donors. Proxies of exposure to repetitive head impacts included years of exposure and age of first exposure to American football play. Informants completed the Functional Activities Questionnaire, Behavior Rating Inventory of Executive Function-Adult Version (Behavioral Regulation Index), and Barratt Impulsiveness Scale-11. Associations between myelin-associated glycoprotein and proteolipid protein 1 with exposure proxies and clinical scales were tested. Of the 205 male brain donors who played amateur and professional football, the mean age was 67.17 (SD = 16.78), and 75.9% (n = 126) were reported by informants to be functionally impaired prior to death. Myelin-associated glycoprotein and proteolipid protein 1 correlated with the ischaemic injury scale score, a global indicator of cerebrovascular disease (r = -0.23 and -0.20, respectively, Ps < 0.01). Chronic traumatic encephalopathy was the most common neurodegenerative disease (n = 151, 73.7%). Myelin-associated glycoprotein and proteolipid protein 1 were not associated with chronic traumatic encephalopathy status, but lower proteolipid protein 1 was associated with more severe chronic traumatic encephalopathy (P = 0.03). Myelin-associated glycoprotein and proteolipid protein 1 were not associated with other neurodegenerative disease pathologies. More years of football play was associated with lower proteolipid protein 1 [beta = -2.45, 95% confidence interval (CI) [-4.52, -0.38]] and compared with those who played <11 years of football (n = 78), those who played 11 or more years (n = 128) had lower myelin-associated glycoprotein (mean difference = 46.00, 95% CI [5.32, 86.69]) and proteolipid protein 1 (mean difference = 24.72, 95% CI [2.40, 47.05]). Younger age of first exposure corresponded to lower proteolipid protein 1 (beta = 4.35, 95% CI [0.25, 8.45]). Among brain donors who were aged 50 or older (n = 144), lower proteolipid protein 1 (beta = -0.02, 95% CI [-0.047, -0.001]) and myelin-associated glycoprotein (beta = -0.01, 95% CI [-0.03, -0.002]) were associated with higher Functional Activities Questionnaire scores. Lower myelin-associated glycoprotein correlated with higher Barratt Impulsiveness Scale-11 scores (beta = -0.02, 95% CI [-0.04, -0.0003]). Results suggest that decreased myelin may represent a late effect of repetitive head impacts that contributes to the manifestation of cognitive symptoms and impulsivity. Clinical-pathological correlation studies with prospective objective clinical assessments are needed to confirm our findings.

Cerebral Gray and White Matter Monogalactosyl Diglyceride Levels Rise with the Progression of Alzheimer's Disease

BACKGROUND

Multiple studies have reported brain lipidomic abnormalities in Alzheimer's disease (AD) that affect glycerophospholipids, sphingolipids, and fatty acids. However, there is no consensus regarding the nature of these abnormalities, and it is unclear if they relate to disease progression.

OBJECTIVE

Monogalactosyl diglycerides (MGDGs) are a class of lipids which have been recently detected in the human brain. We sought to measure their levels in postmortem human brain and determine if these levels correlate with the progression of the AD-related traits.

METHODS

We measured MGDGs by ultrahigh performance liquid chromatography tandem mass spectrometry in postmortem dorsolateral prefrontal cortex gray matter and subcortical corona radiata white matter samples derived from three cohorts of participants: the Framingham Heart Study, the Boston University Alzheimer's Disease Research Center, and the Arizona Study of Aging and Neurodegenerative Disorders/Brain and Body Donation Program (total n = 288).

RESULTS

We detected 40 molecular species of MGDGs (including diacyl and alkyl/acyl compounds) and found that the levels of 29 of them, as well as total MGDG levels, are positively associated with AD-related traits including pathologically confirmed AD diagnosis, clinical dementia rating, Braak and Braak stage, neuritic plaque score, phospho-Tau AT8 immunostaining density, levels of phospho-Tau396 and levels of Aβ40. Increased MGDG levels were present in both gray and white matter, indicating that they are widespread and likely associated with myelin-producing oligodendrocytes-the principal cell type of white matter.

CONCLUSIONS

Our data implicate the MGDG metabolic defect as a central correlate of clinical and pathological progression in AD.

Neuropathologic validation of the Alzheimer's Questionnaire

The Alzheimer's Questionnaire (AQ) is an informant-based screening tool with good diagnostic accuracy for Alzheimer's disease (AD) and amnestic mild cognitive impairment (aMCI). The aim of this study is to validate the AQ with AD-associated neuritic plaque (NP) and neurofibrillary tangle (NFT) pathology. Data from 205 prospectively followed autopsy cases clinically classified as AD (n = 90), aMCI (n = 42), or cognitively unimpaired (CU, n = 73) were used. Semi-quantitative measures of NP and NFT pathology were correlated with the AQ, Clinical Dementia Rating Sum of Boxes (CDR-SOB), and the Mini-Mental State Exam (MMSE). The AQ correlated significantly (p < 0.001) with NP load (r = 0.37) and NFT load (r = 0.57). The MMSE and CDR-SOB showed similar correlations with NP load (r = - 0.37, r = 0.35, respectively) and NFT load (r = - 0.58, r = 0.55, respectively). The AQ correlates well with NP and NFT pathology of AD, which provides additional confidence to clinicians using the AQ to screen for AD-related cognitive impairment.

Tau phosphorylation sites serine202 and serine396 are differently altered in chronic traumatic encephalopathy and Alzheimer's disease

INTRODUCTION

Chronic traumatic encephalopathy (CTE) is a neurodegenerative tauopathy associated with repetitive head impacts (RHI) typically sustained by contact sport athletes. Post-translation modifications to tau in CTE have not been well delineated or compared to Alzheimer's disease (AD).

METHODS

We measured phosphorylated tau epitopes within dorsolateral frontal cortex from post mortem brains with neither CTE nor AD (n = 108), CTE (n = 109), AD (n = 223), and both CTE and AD (n = 33).

RESULTS

Levels of hyperphosphorylated tau (p-tau)202 , p-tau231 , and p-tau396 were significantly increased in CTE. Total years of RHI exposure was significantly associated with increased p-tau202 levels (P = .001), but not p-tau396 . Instead, p-tau396 was most closely related to amyloid beta (Aβ)1-42 levels (P < .001). The p-tau202 :p-tau396 ratio was significantly increased in early and late CTE compared to AD.

DISCUSSION

In frontal cortex, p-tau202 is the most upregulated p-tau species in CTE, while p-tau396 is most increased in AD. p-tau202 and p-tau396 measurements may aid in developing biomarkers for disease.

Determining Vascular Risk Factors for Dementia and Dementia Risk Prediction Across Mid- to Later Life: The Framingham Heart Study

BACKGROUND AND OBJECTIVES

The association between vascular risk factors and dementia varies with age, making generalizability of dementia risk prediction rules to individuals of different ages challenging. We determined the most important vascular risk factors for inclusion in age-specific dementia risk scores.

METHODS

Framingham Heart Study Original and Offspring cohort participants with available data on the Framingham Stroke Risk Profile (FSRP) at midlife (age 55; n = 4,899, 57% women), late life (ages 65 or 70), or later life (ages 75 or 80 [n = 2,386, 62% women]) were followed for 10-year incident dementia risk from ages 65, 70, 75, and 80.

RESULTS

Age- and sex-adjusted midlife risk factors associated with 10-year risk of dementia from age 65 included FSRP (hazard ratio [HR] 1.16, 95% CI 1.06-1.26, per 1 SD increment in log-transformed score), diabetes mellitus (DM; HR 4.31, 95% CI 1.97-9.43), and systolic blood pressure (SBP; HR 1.12, 95% CI 1.02-1.24, per 10 mm Hg increment). Late-life risk factors associated with 10-year incident dementia from ages 65 or 70 included FSRP (age 65 only: HR 1.06, 95% CI 1.02-1.10), antihypertensive use (age 65 reported: HR 1.66, 95% CI 1.12-2.46), DM (age 65 reported: HR 1.96, 95% CI 1.09-3.52), atrial fibrillation (age 65 reported: HR 2.30, 95% CI 1.00-5.27), nonstroke cardiovascular disease (nsCVD; age 65 reported: HR 1.95, 95% CI 1.24-3.07), and stroke (age 70 only: HR 3.61, 95% CI 2.21-5.92). Later-life risk factors associated with 10-year incident dementia from ages 75 or 80 included antihypertensive use (age 80 only: HR 0.74, 95% CI 0.62-0.89), DM (age 80 reported: HR 1.40, 95% CI 1.04-1.89), atrial fibrillation (age 80 reported: HR 1.43, 95% CI 1.07-1.92), and stroke (age 80 reported: HR 1.63, 95% CI 1.13-2.35). In stepwise models, SBP and DM at age 55, nsCVD at age 65, DM and stroke at ages 70 and 75, and DM, stroke, and use of antihypertensives (protective) at age 80 were the most important vascular risk factors for dementia.

DISCUSSION

Our findings support the use of age-specific dementia risk scores, which should prioritize including, at age 55, SBP and DM; at age 65, nsCVD; at ages 70 and 75, DM and stroke; and at age 80, DM, stroke, and antihypertensive use.

Platelet Function Is Associated With Dementia Risk in the Framingham Heart Study

Background Vascular function is compromised in Alzheimer disease (AD) years before amyloid and tau pathology are detected and a substantial body of work shows abnormal platelet activation states in patients with AD. The aim of our study was to investigate whether platelet function in middle age is independently associated with future risk of AD. Methods and Results We examined associations of baseline platelet function with incident dementia risk in the community-based FHS (Framingham Heart Study) longitudinal cohorts. The association between platelet function and risk of dementia was evaluated using the cumulative incidence function and inverse probability weighted Cox proportional cause-specific hazards regression models, with adjustment for demographic and clinical covariates. Platelet aggregation response was measured by light transmission aggregometry. The final study sample included 1847 FHS participants (average age, 53.0 years; 57.5% women). During follow-up (median, 20.5 years), we observed 154 cases of incident dementia, of which 121 were AD cases. Results from weighted models indicated that platelet aggregation response to adenosine diphosphate 1.0 µmol/L was independently and positively associated with dementia risk, and it was preceded in importance only by age and hypertension. Sensitivity analyses showed associations with the same directionality for participants defined as adenosine diphosphate hyper-responders, as well as the platelet response to 0.1 µmol/L epinephrine. Conclusions Our study shows individuals free of antiplatelet therapy with a higher platelet response are at higher risk of dementia in late life during a 20-year follow-up, reinforcing the role of platelet function in AD risk. This suggests that platelet phenotypes may be associated with the rate of dementia and potentially have prognostic value.

The Neutrophil to Lymphocyte Ratio Is Associated With the Risk of Subsequent Dementia in the Framingham Heart Study

Objective: Active neutrophils are important contributors to Alzheimer’s disease (AD) pathology through the formation of capillary stalls that compromise cerebral blood flow (CBF) and through aberrant neutrophil signaling that advances disease progression. The neutrophil to lymphocyte ratio (NLR) is a proxy of neutrophil-mediated inflammation, and higher NLR is found in persons diagnosed with clinical AD. The objective of this study was to investigate whether increased NLR in older adults is independently associated with the risk of subsequent dementia.

Methods: We examined associations of baseline NLR with incident dementia risk in the community-based Framingham Heart Study (FHS) longitudinal cohorts. The association between NLR and risk of dementia was evaluated using the cumulative incidence function (CIF) and inverse probability-weighted Cox proportional cause-specific hazards regression models, with adjustment for age, sex, body mass index (BMI), systolic and diastolic blood pressure, diabetes, current smoking status, low-density lipoprotein (LDH), high-density lipoprotein (LDL), total cholesterol, triglycerides, and history of cardiovascular disease (CVD). Random forest survival models were used to evaluate the relative predictive value of the model covariates on dementia risk.

Results: The final study sample included 1,648 participants with FHS (average age, 69 years; 56% women). During follow-up (median, 5.9 years), we observed 51 cases of incident dementia, of which 41 were AD cases. Results from weighted models suggested that the NLR was independently associated with incident dementia, and it was preceded in predictive value only by age, history of CVD, and blood pressure at baseline.

Conclusion: Our study shows that individuals with higher NLR are at a greater risk of subsequent dementia during a 5.9-year follow-up period. Further evaluating the role of neutrophil-mediated inflammation in AD progression may be warranted.

Mid- to Late-Life Body Mass Index and Dementia Risk: 38 Years of Follow-up of the Framingham Study

Growing evidence relates body mass index (BMI) to poorer health outcomes; however, results across studies associating BMI and dementia are conflicting. A total of 3,632 Framingham Offspring participants aged 20 to 60 years at their second health examination (1979-1983) were included in this study, with 190 cases of incident dementia identified by 2017. Cox proportional hazards regression models were fitted to investigate the association of BMI at each of their 8 exams as a baseline for dementia risk and the associations between obesity and dementia across age groups. Spline models were fitted to investigate nonlinear associations between BMI and dementia. Each 1-unit increase in BMI at ages 40-49 years was associated with higher risk of dementia, but with lower risk after age 70 years. Obesity at ages 40-49 years was associated with higher risk of dementia. Overall, the relationship between BMI and dementia risk was heterogeneous across the adult age range. Monitoring BMI at different ages might mediate risk for dementia across an individual's lifetime.

Synaptic proteins associated with cognitive performance and neuropathology in older humans revealed by multiplexed fractionated proteomics

Alzheimer's disease (AD) is defined by the presence of abundant amyloid-β (Aβ) and tau neuropathology. While this neuropathology is necessary for AD diagnosis, it is not sufficient for causing cognitive impairment. Up to one third of community dwelling older adults harbor intermediate to high levels of AD neuropathology at death yet demonstrate no significant cognitive impairment. Conversely, there are individuals who exhibit dementia with no gross explanatory neuropathology. In prior studies, synapse loss correlated with cognitive impairment. To understand how synaptic composition changes in relation to neuropathology and cognition, multiplexed liquid chromatography mass-spectrometry was used to quantify enriched synaptic proteins from the parietal association cortex of 100 subjects with contrasting levels of AD pathology and cognitive performance. 123 unique proteins were significantly associated with diagnostic category. Functional analysis showed enrichment of serotonin release and oxidative phosphorylation categories in normal (cognitively unimpaired, low neuropathology) and "resilient" (unimpaired despite AD pathology) individuals. In contrast, frail individuals, (low pathology, impaired cognition) showed a metabolic shift towards glycolysis and increased presence of proteasome subunits.

Linguistic markers predict onset of Alzheimer's disease

BACKGROUND

The aim of this study is to use classification methods to predict future onset of Alzheimer's disease in cognitively normal subjects through automated linguistic analysis.

METHODS

To study linguistic performance as an early biomarker of AD, we performed predictive modeling of future diagnosis of AD from a cognitively normal baseline of Framingham Heart Study participants. The linguistic variables were derived from written responses to the cookie-theft picture-description task. We compared the predictive performance of linguistic variables with clinical and neuropsychological variables. The study included 703 samples from 270 participants out of which a dataset consisting of a single sample from 80 participants was held out for testing. Half of the participants in the test set developed AD symptoms before 85 years old, while the other half did not. All samples in the test set were collected during the cognitively normal period (before MCI). The mean time to diagnosis of mild AD was 7.59 years.

FINDINGS

Significant predictive power was obtained, with AUC of 0.74 and accuracy of 0.70 when using linguistic variables. The linguistic variables most relevant for predicting onset of AD have been identified in the literature as associated with cognitive decline in dementia.

INTERPRETATION

The results suggest that language performance in naturalistic probes expose subtle early signs of progression to AD in advance of clinical diagnosis of impairment.

FUNDING

Pfizer, Inc. provided funding to obtain data from the Framingham Heart Study Consortium, and to support the involvement of IBM Research in the initial phase of the study. The data used in this study was supported by Framingham Heart Study's National Heart, Lung, and Blood Institute contract (N01-HC-25195), and by grants from the National Institute on Aging grants (R01-AG016495, R01-AG008122) and the National Institute of Neurological Disorders and Stroke (R01-NS017950).

The Expression of Activin Receptor-Like Kinase 1 (ACVRL1/ALK1) in Hippocampal Arterioles Declines During Progression of Alzheimer's Disease

Cerebral amyloid angiopathy (CAA) in Alzheimer’s disease (AD)—deposition of beta amyloid (Aβ) within the walls of cerebral blood vessels—typically accompanies Aβ buildup in brain parenchyma and causes abnormalities in vessel structure and function. We recently demonstrated that the immunoreactivity of activin receptor-like kinase 1 (ALK1), the type I receptor for circulating BMP9/BMP10 (bone morphogenetic protein) signaling proteins, is reduced in advanced, but not early stages of AD in CA3 pyramidal neurons. Here we characterize vascular expression of ALK1 in the context of progressive AD pathology accompanied by amyloid angiopathy in postmortem hippocampi using immunohistochemical methods. Hippocampal arteriolar wall ALK1 signal intensity was 35% lower in AD patients (Braak and Braak Stages IV and V [BBIV-V]; clinical dementia rating [CDR1-2]) as compared with subjects with early AD pathologic changes but either cognitively intact or with minimal cognitive impairment (BBIII; CDR0-0.5). The intensity of Aβ signal in arteriolar walls was similar in all analyzed cases. These data suggest that, as demonstrated previously for specific neuronal populations, ALK1 expression in blood vessels is also vulnerable to the AD pathophysiologic process, perhaps related to CAA. However, cortical arterioles may remain responsive to the ALK1 ligands, such as BMP9 and BMP10 in early and moderate AD.

Cardiovascular health, genetic risk, and risk of dementia in the Framingham Heart Study

OBJECTIVE

To determine the joint role of ideal cardiovascular health (CVH) and genetic risk on risk of dementia.

METHODS

We categorized CVH on the basis of the American Heart Association Ideal CVH Index and genetic risk through a genetic risk score (GRS) of common genetic variants and the APOE ε4 genotype in 1,211 Framingham Heart Study (FHS) offspring cohort participants. We used multivariable Cox proportional hazards regression models to examine the association between CVH, genetic risk, and incident all-cause dementia with up to 10 years of follow-up (mean 8.4 years, 96 incident dementia cases), adjusting for age, sex, and education.

RESULTS

We observed that a high GRS (>80th percentile) was associated with a 2.6-fold risk of dementia (95% confidence interval [CI] of hazard ratio [HR] 1.23-5.29; p = 0.012) compared with having a low GRS (<20th percentile); carrying at least 1 APOE ε4 allele was associated with a 2.3-fold risk of dementia compared with not carrying an APOE ε4 allele (95% CI of HR 1.49-3.53; p = 0.0002), and having a favorable CVH showed a 0.45-fold lower risk of dementia (95% CI of HR 0.20-1.01; p = 0.0527) compared to having an unfavorable CVH when all 3 components were included in the model. We did not observe an interaction between CVH and GRS (p = 0.99) or APOE ε4 (p = 0.16).

CONCLUSIONS

We observed that both genetic risk and CVH contribute additively to dementia risk.

Development and validation of an interpretable deep learning framework for Alzheimer's disease classification

Alzheimer's disease is the primary cause of dementia worldwide, with an increasing morbidity burden that may outstrip diagnosis and management capacity as the population ages. Current methods integrate patient history, neuropsychological testing and MRI to identify likely cases, yet effective practices remain variably applied and lacking in sensitivity and specificity. Here we report an interpretable deep learning strategy that delineates unique Alzheimer's disease signatures from multimodal inputs of MRI, age, gender, and Mini-Mental State Examination score. Our framework linked a fully convolutional network, which constructs high resolution maps of disease probability from local brain structure to a multilayer perceptron and generates precise, intuitive visualization of individual Alzheimer's disease risk en route to accurate diagnosis. The model was trained using clinically diagnosed Alzheimer's disease and cognitively normal subjects from the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset (n = 417) and validated on three independent cohorts: the Australian Imaging, Biomarker and Lifestyle Flagship Study of Ageing (AIBL) (n = 382), the Framingham Heart Study (n = 102), and the National Alzheimer's Coordinating Center (NACC) (n = 582). Performance of the model that used the multimodal inputs was consistent across datasets, with mean area under curve values of 0.996, 0.974, 0.876 and 0.954 for the ADNI study, AIBL, Framingham Heart Study and NACC datasets, respectively. Moreover, our approach exceeded the diagnostic performance of a multi-institutional team of practicing neurologists (n = 11), and high-risk cerebral regions predicted by the model closely tracked post-mortem histopathological findings. This framework provides a clinically adaptable strategy for using routinely available imaging techniques such as MRI to generate nuanced neuroimaging signatures for Alzheimer's disease diagnosis, as well as a generalizable approach for linking deep learning to pathophysiological processes in human disease.

Duration of American Football Play and Chronic Traumatic Encephalopathy

OBJECTIVE

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease associated with exposure to contact and collision sports, including American football. We hypothesized a dose-response relationship between duration of football played and CTE risk and severity.

METHODS

In a convenience sample of 266 deceased American football players from the Veterans Affairs-Boston University-Concussion Legacy Foundation and Framingham Heart Study Brain Banks, we estimated the association of years of football played with CTE pathological status and severity. We evaluated the ability of years played to classify CTE status using receiver operating characteristic curve analysis. Simulation analyses quantified conditions that might lead to selection bias.

RESULTS

In total, 223 of 266 participants met neuropathological diagnostic criteria for CTE. More years of football played were associated with having CTE (odds ratio [OR] = 1.30 per year played, 95% confidence interval [CI] = 1.19-1.41; p = 3.8 × 10-9 ) and with CTE severity (severe vs mild; OR = 1.14 per year played, 95% CI = 1.07-1.22; p = 3.1 × 10-4 ). Participants with CTE were 1/10th as likely to have played <4.5 years (negative likelihood ratio [LR] = 0.102, 95% CI = 0.100-0.105) and were 10 times as likely to have played >14.5 years (positive LR = 10.2, 95% CI = 9.8-10.7) compared with participants without CTE. Sensitivity and specificity were maximized at 11 years played. Simulation demonstrated that years played remained adversely associated with CTE status when years played and CTE status were both related to brain bank selection across widely ranging scenarios.

INTERPRETATION

The odds of CTE double every 2.6 years of football played. After accounting for brain bank selection, the magnitude of the relationship between years played and CTE status remained consistent. ANN NEUROL 2020;87:116-131.

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.

NIA-AA Research Framework: Toward a biological definition of Alzheimer's disease

In 2011, the National Institute on Aging and Alzheimer’s Association created separate diagnostic recommendations for the preclinical, mild cognitive impairment, and dementia stages of Alzheimer’s disease. Scientific progress in the interim led to an initiative by the National Institute on Aging and Alzheimer’s Association to update and unify the 2011 guidelines. This unifying update is labeled a “research framework” because its intended use is for observational and interventional research, not routine clinical care. In the National Institute on Aging and Alzheimer’s Association Research Framework, Alzheimer’s disease (AD) is defined by its underlying pathologic processes that can be documented by postmortem examination or in vivo by biomarkers. The diagnosis is not based on the clinical consequences of the disease (i.e., symptoms/signs) in this research framework, which shifts the definition of AD in living people from a syndromal to a biological construct. The research framework focuses on the diagnosis of AD with biomarkers in living persons. Biomarkers are grouped into those of β amyloid deposition, pathologic tau, and neurodegeneration [AT(N)]. This ATN classification system groups different biomarkers (imaging and biofluids) by the pathologic process each measures. The AT(N) system is flexible in that new biomarkers can be added to the three existing AT(N) groups, and new biomarker groups beyond AT(N) can be added when they become available. We focus on AD as a continuum, and cognitive staging may be accomplished using continuous measures. However, we also outline two different categorical cognitive schemes for staging the severity of cognitive impairment: a scheme using three traditional syndromal categories and a six-stage numeric scheme. It is important to stress that this framework seeks to create a common language with which investigators can generate and test hypotheses about the interactions among different pathologic processes (denoted by biomarkers) and cognitive symptoms. We appreciate the concern that this biomarker-based research framework has the potential to be misused. Therefore, we emphasize, first, it is premature and inappropriate to use this research framework in general medical practice. Second, this research framework should not be used to restrict alternative approaches to hypothesis testing that do not use biomarkers. There will be situations where biomarkers are not available or requiring them would be counterproductive to the specific research goals (discussed in more detail later in the document). Thus, biomarker-based research should not be considered a template for all research into age-related cognitive impairment and dementia; rather, it should be applied when it is fit for the purpose of the specific research goals of a study. Importantly, this framework should be examined in diverse populations. Although it is possible that β-amyloid plaques and neurofibrillary tau deposits are not causal in AD pathogenesis, it is these abnormal protein deposits that define AD as a unique neurodegenerative disease among different disorders that can lead to dementia. We envision that defining AD as a biological construct will enable a more accurate characterization and understanding of the sequence of events that lead to cognitive impairment that is associated with AD, as well as the multifactorial etiology of dementia. This approach also will enable a more precise approach to interventional trials where specific pathways can be targeted in the disease process and in the appropriate people.

Clinical prevalence of Lewy body dementia

Background

The prevalence of dementia with Lewy bodies (DLB) and dementia in Parkinson’s disease (PDD) in routine clinical practice is unclear. Prevalence rates observed in clinical and population-based cohorts and neuropathological studies vary greatly. Small sample sizes and methodological factors in these studies limit generalisability to clinical practice.

Methods

We investigated prevalence in a case series across nine secondary care services over an 18-month period, to determine how commonly DLB and PDD cases are diagnosed and reviewed within two regions of the UK.

Results

Patients with DLB comprised 4.6% (95% CI 4.0–5.2%) of all dementia cases. DLB was represented in a significantly higher proportion of dementia cases in services in the North East (5.6%) than those in East Anglia (3.3%; χ² = 13.6, p < 0.01). DLB prevalence in individual services ranged from 2.4 to 5.9%. PDD comprised 9.7% (95% CI 8.3–11.1%) of Parkinson’s disease cases. No significant variation in PDD prevalence was observed between regions or between services.

Conclusions

We found that the frequency of clinical diagnosis of DLB varied between geographical regions in the UK, and that the prevalence of both DLB and PDD was much lower than would be expected in this case series, suggesting considerable under-diagnosis of both disorders. The significant variation in DLB diagnostic rates between these two regions may reflect true differences in disease prevalence, but more likely differences in diagnostic practice. The systematic introduction of more standardised diagnostic practice could improve the rates of diagnosis of both conditions.

Interaction Between Midlife Blood Glucose and APOE Genotype Predicts Later Alzheimer's Disease Pathology

Elevated blood glucose and the apolipoprotein (APOE) ɛ4 allele have both been associated with increased dementia risk; however, the neuropathological mechanisms underlying these associations remain unclear. We examined the impact of APOE genotype and midlife blood glucose on post-mortem vascular and Alzheimer's disease (AD) neuropathology. Ninety-four participants from the Framingham Heart Study without diagnosed diabetes underwent health examination at midlife and brain autopsy at death. Histopathological measures of vascular and AD neuropathology were obtained and analyzed. Results demonstrated that, among APOE ɛ4 carriers, elevated blood glucose was associated with more severe AD pathology. There was no such relationship with vascular pathology. In a relatively healthy sample with low vascular risk burden, midlife elevated blood glucose was associated with greater AD pathology among APOE ɛ4 carriers. A better understanding of interactive effects of APOE genotype and vascular risk on neuropathology has implications for identification of individuals at risk for decline and long-term preventive treatment.

Genetic Interaction with Plasma Lipids on Alzheimer's Disease in the Framingham Heart Study

Epidemiological and genetic studies have pointed to the role of cholesterol in Alzheimer's disease (AD). We explored the interaction of a genetic risk score (GRS) of AD risk alleles with mid-life plasma lipid levels (LDL-C, HDL-C, and triglycerides) on risk for AD in the Framingham Heart Study (FHS). Mid-life (between the ages of 40-60 years old) lipid levels were obtained from individuals in the FHS Original and Offspring cohorts (157 cases and 2,882 controls) with genetic data and AD status available. Cox proportional hazards regression was performed to test the interaction between mid-life lipid levels and an AD GRS, as well as the individual contributing SNPs, on risk of incident AD adjusting for age, sex, and cohort. We found a significant interaction between a GRS of AD loci and log triglyceride levels on risk of clinical AD (p = 0.006), but no interaction of the GRS with HDL-C (p = 0.458) or LDL-C (p = 0.366). We then tested the interaction between the individual SNPs contributing to the GRS and log triglycerides. We found two SNPs that had interactions with triglycerides on AD risk that reached a p-value < 0.05 (rs11218343 and APOEɛ4). The association between some AD SNPs and risk of AD may be modified by triglyceride levels. Furthermore, sequential testing of a GRS with a set of traits on disease followed by testing individual SNPs for interaction provides a framework for narrowing the associations that need to be tested for interaction analyses. Replication is needed to confirm these findings.

Immunohistochemical Analysis of Activin Receptor-Like Kinase 1 (ACVRL1/ALK1) Expression in the Rat and Human Hippocampus: Decline in CA3 During Progression of Alzheimer's Disease

The pathophysiology of Alzheimer's disease (AD) includes signaling defects mediated by the transforming growth factor β-bone morphogenetic protein-growth and differentiation factor (TGFβ-BMP-GDF) family of proteins. In animal models of AD, administration of BMP9/GDF2 improves memory and reduces amyloidosis. The best characterized type I receptor of BMP9 is ALK1. We characterized ALK1 expression in the hippocampus using immunohistochemistry. In the rat, ALK1 immunoreactivity was found in CA pyramidal neurons, most frequently and robustly in the CA2 and CA3 fields. In addition, there were sporadic ALK1-immunoreactive cells in the stratum oriens, mainly in CA1. The ALK1 expression pattern in human hippocampus was similar to that of rat. Pyramidal neurons within the CA2, CA3, and CA4 were strongly ALK1-immunoreactive in hippocampi of cognitively intact subjects with no neurofibrillary tangles. ALK1 signal was found in the axons of alveus and fimbria, and in the neuropil across CA fields. Relatively strongest ALK1 neuropil signal was observed in CA1 where pyramidal neurons were occasionally ALK1-immunoractive. As in the rat, horizontally oriented neurons in the stratum oriens of CA1 were both ALK1- and GAD67-immunoreactive. Analysis of ALK1 immunoreactivity across stages of AD pathology revealed that disease progression was characterized by overall reduction of the ALK1 signal in CA3 in advanced, but not early, stages of AD. These data suggest that the CA3 pyramidal neurons may remain responsive to the ALK1 ligands, e.g., BMP9, during initial stages of AD and that ALK1 may constitute a therapeutic target in early and moderate AD.

Whole blood gene expression and white matter Hyperintensities

Background

White matter hyperintensities (WMH) are an important biomarker of cumulative vascular brain injury and have been associated with cognitive decline and an increased risk of dementia, stroke, depression, and gait impairments. The pathogenesis of white matter lesions however, remains uncertain. The characterization of gene expression profiles associated with WMH might help uncover molecular mechanisms underlying WMH.

Methods

We performed a transcriptome-wide association study of gene expression profiles with WMH in 3248 participants from the Framingham Heart Study using the Affymetrix Human Exon 1.0 ST Array.

Results

We identified 13 genes that were significantly associated with WMH (FDR < 0.05) after adjusting for age, sex and blood cell components. Many of these genes are involved in inflammation-related pathways.

Conclusion

Thirteen genes were significantly associated with WMH. Our study confirms the hypothesis that inflammation might be an important factor contributing to white matter lesions. Future work is needed to explore if these gene products might serve as potential therapeutic targets.

Electronic supplementary material

The online version of this article (10.1186/s13024-017-0209-5) contains supplementary material, which is available to authorized users.

Modeling the Relationships Among Late-Life Body Mass Index, Cerebrovascular Disease, and Alzheimer's Disease Neuropathology in an Autopsy Sample of 1,421 Subjects from the National Alzheimer's Coordinating Center Data Set

The relationship between late-life body mass index (BMI) and Alzheimer's disease (AD) is poorly understood due to the lack of research in samples with autopsy-confirmed AD neuropathology (ADNP). The role of cerebrovascular disease (CVD) in the interplay between late-life BMI and ADNP is unclear. We conducted a retrospective longitudinal investigation and used joint modeling of linear mixed effects to investigate causal relationships among repeated antemortem BMI measurements, CVD (quantified neuropathologically), and ADNP in an autopsy sample of subjects across the AD clinical continuum. The sample included 1,421 subjects from the National Alzheimer's Coordinating Center's Uniform Data Set and Neuropathology Data Set with diagnoses of normal cognition (NC; n = 234), mild cognitive impairment (MCI; n = 201), or AD dementia (n = 986). ADNP was defined as moderate to frequent neuritic plaques and Braak stageIII-VI. Ischemic Injury Scale (IIS) operationalized CVD. Joint modeling examined relationships among BMI, IIS, and ADNP in the overall sample and stratified by initial visit Clinical Dementia Rating score. Subject-specific random intercept for BMI was the predictor for ADNP due to minimal BMI change (p = 0.3028). Analyses controlling for demographic variables and APOE ɛ4 showed lower late-life BMI predicted increased odds of ADNP in the overall sample (p < 0.001), and in subjects with CDR of 0 (p = 0.0021) and 0.5 (p = 0.0012), but not ≥1.0 (p = 0.2012). Although higher IIS predicted greater odds of ADNP (p < 0.0001), BMI did not predict IIS (p = 0.2814). The current findings confirm lower late-life BMI confers increased odds for ADNP. Lower late-life BMI may be a preclinical indicator of underlying ADNP.

Impact of multiple pathologies on the threshold for clinically overt dementia

Longitudinal clinical-pathological studies have increasingly recognized the importance of mixed pathologies (the coexistence of one or more neurodegenerative and cerebrovascular disease pathologies) as important factors in the development of Alzheimer's disease (AD) and other forms of dementia. Older persons with AD pathology, often have concomitant cerebrovascular disease pathologies (macroinfarcts, microinfarcts, atherosclerosis, arteriolosclerosis, cerebral amyloid angiopathy) as well as other concomitant neurodegenerative disease pathologies (Lewy bodies, TDP-43, hippocampal sclerosis). These additional pathologies lower the threshold for clinical diagnosis of AD. Many of these findings from pathologic studies, especially for CVD, have been confirmed using sophisticated neuroimaging technologies. In vivo biomarker studies are necessary to provide an understanding of specific pathologic contributions and time course relationships along the spectrum of accumulating pathologies. In this review, we provide a clinical-pathological perspective on the role of multiple brain pathologies in dementia followed by a review of the available clinical and biomarker data on some of the mixed pathologies.

Methionine Sulfoxide Reductase-B3 (MsrB3) Protein Associates with Synaptic Vesicles and its Expression Changes in the Hippocampi of Alzheimer's Disease Patients

Genome-wide association studies (GWAS) identified susceptibility loci associated with decreased hippocampal volume, and found hippocampal subfield-specific effects at MSRB3 (methionine sulfoxide reductase-B3). The MSRB3 locus was also linked to increased risk for late onset Alzheimer's disease (AD). In this study, we uncovered novel sites of MsrB3 expression in CA pyramidal layer and arteriolar walls by using automated immunohistochemistry on hippocampal sections from 23 individuals accompanied by neuropathology reports and clinical dementia rating scores. Controls, cognitively intact subjects with no hippocampal neurofibrillary tangles, exhibited MsrB3 signal as distinct but rare puncta in CA1 pyramidal neuronal somata. In CA3, however, MsrB3-immunoreactivity was strongest in the neuropil of the pyramidal layer. These patterns were replicated in rodent hippocampi where ultrastructural and immunohistofluorescence analysis revealed MsrB3 signal associated with synaptic vesicles and colocalized with mossy fiber terminals. In AD subjects, the number of CA1 pyramidal neurons with frequent, rather than rare, MsrB3-immunoreactive somatic puncta increased in comparison to controls. This change in CA1 phenotype correlated with the occurrence of AD pathological hallmarks. Moreover, the intensity of MsrB3 signal in the neuropil of CA3 pyramidal layer correlated with the signal pattern in neurons of CA1 pyramidal layer that was characteristic of cognitively intact individuals. Finally, MsrB3 signal in the arteriolar walls in the hippocampal white matter decreased in AD patients. This characterization of GWAS-implicated MSRB3 protein expression in human hippocampus suggests that patterns of neuronal and vascular MsrB3 protein expression reflect or underlie pathology associated with AD.

Limiting Factors of Brain Donation in Neurodegenerative Diseases: The Example of French Memory Clinics

Postmortem neuropathological examination of the brain is essential in neurodegenerative diseases, to ensure accurate diagnosis, to obtain an a posteriori critical assessment of the adequacy of clinical care, and to validate new biomarkers, but is only rarely performed. The purpose of this study was to assess factors limiting brain donation, such as reluctance of physicians to seek donation consent, opposition from patients and families, and organizational constraints. We conducted a survey across French memory clinics and major neuropathological centers. Few postmortem examinations were performed annually, as less than one third of the centers had performed at least five autopsies, and 41% had performed none. The main limiting factor was the lack of donation requests made by physicians, as half of them never approach patients for brain donation. Reasons for not seeking donation consent often include discomfort broaching the subject and lack of awareness of the medical and scientific benefit of postmortems (77%), organizational constraints (61%), and overestimation of families' negative reaction (51%). Family refusals represented a second major obstacle, and were often caused by misconceptions. Identifying and addressing these biases early could help improve physicians' rate of making requests and the public's awareness about the importance of brain donation.

Incidence of Dementia over Three Decades in the Framingham Heart Study

BACKGROUND

The prevalence of dementia is expected to soar as the average life expectancy increases, but recent estimates suggest that the age-specific incidence of dementia is declining in high-income countries. Temporal trends are best derived through continuous monitoring of a population over a long period with the use of consistent diagnostic criteria. We describe temporal trends in the incidence of dementia over three decades among participants in the Framingham Heart Study.

METHODS

Participants in the Framingham Heart Study have been under surveillance for incident dementia since 1975. In this analysis, which included 5205 persons 60 years of age or older, we used Cox proportional-hazards models adjusted for age and sex to determine the 5-year incidence of dementia during each of four epochs. We also explored the interactions between epoch and age, sex, apolipoprotein E ε4 status, and educational level, and we examined the effects of these interactions, as well as the effects of vascular risk factors and cardiovascular disease, on temporal trends.

RESULTS

The 5-year age- and sex-adjusted cumulative hazard rates for dementia were 3.6 per 100 persons during the first epoch (late 1970s and early 1980s), 2.8 per 100 persons during the second epoch (late 1980s and early 1990s), 2.2 per 100 persons during the third epoch (late 1990s and early 2000s), and 2.0 per 100 persons during the fourth epoch (late 2000s and early 2010s). Relative to the incidence during the first epoch, the incidence declined by 22%, 38%, and 44% during the second, third, and fourth epochs, respectively. This risk reduction was observed only among persons who had at least a high school diploma (hazard ratio, 0.77; 95% confidence interval, 0.67 to 0.88). The prevalence of most vascular risk factors (except obesity and diabetes) and the risk of dementia associated with stroke, atrial fibrillation, or heart failure have decreased over time, but none of these trends completely explain the decrease in the incidence of dementia.

CONCLUSIONS

Among participants in the Framingham Heart Study, the incidence of dementia has declined over the course of three decades. The factors contributing to this decline have not been completely identified. (Funded by the National Institutes of Health.).

Diagnostic value of lobar microbleeds in individuals without intracerebral hemorrhage

INTRODUCTION

The Boston criteria are the basis for a noninvasive diagnosis of cerebral amyloid angiopathy (CAA) in the setting of lobar intracerebral hemorrhage (ICH). We assessed the accuracy of these criteria in individuals with lobar microbleeds (MBs) without ICH.

METHODS

We identified individuals aged >55 years having brain magnetic resonance imaging (MRI) and pathological assessment of CAA in a single academic hospital and a community-based population (Framingham Heart Study [FHS]). We determined the positive predictive value (PPV) of the Boston criteria for CAA in both cohorts, using lobar MBs as the only hemorrhagic lesion to fulfill the criteria.

RESULTS

We included 102 individuals: 55 from the hospital-based cohort and 47 from FHS (mean age at MRI 74.7 ± 8.5 and 83.4 ± 10.9 years; CAA prevalence 60% and 46.8%; cases with any lobar MB 49% and 21.3%; and cases with ≥2 strictly lobar MBs 29.1% and 8.5%, respectively). PPV of "probable CAA" (≥2 strictly lobar MBs) was 87.5% (95% confidence interval [CI], 60.4-97.8) and 25% (95% CI, 13.2-78) in hospital and general populations, respectively.

DISCUSSION

Strictly lobar MBs strongly predict CAA in non-ICH individuals when found in a hospital context. However, their diagnostic accuracy in the general population appears limited.

Neurodegeneration and sport

The recent interest in concussion in sport has resulted in significant media focus about chronic traumatic encephalopathy (CTE), although a direct causative link(s) between concussion and CTE is not established. Typically, sport-related CTE occurs in a retired athlete with or without a history of concussion(s) who presents with a constellation of cognitive, mood, and/or behavioral symptoms and who has postmortem findings of tau deposition within the brain. There are many confounding variables, however, that can account for brain tau deposition, including genetic mutations, drugs, normal aging, environmental factors, postmortem brain processing, and toxins. To understand the roles of such factors in neurodegenerative diseases that may occur in athletes, this article reviews some neurodegenerative diseases that may present with similar findings in nonathletes. The article also reviews pathological changes identified with normal aging, and reviews the pathological findings of CTE in light of all these factors. While many of these athletes have a history of exposure to head impacts as a part of contact sport, there is insufficient evidence to establish causation between sports concussion and CTE. It is likely that many of the cases with neuropathological findings represent the normal aging process, the effects of opiate abuse, or a variant of frontotemporal lobar degeneration. Whether particular genetic causes may place athletes at greater risk of neurodegenerative disease is yet to be determined.

Association between neuropathology and brain volume in the Framingham Heart Study

Studies of clinical and community cohorts have shown that antemortem imaging measures of hippocampal volume have correlated with postmortem Alzheimer pathology. Fewer studies have examined the relationship between both Alzheimer and cerebrovascular pathology, and antemortem brain imaging. The aim of this study was to correlate antemortem brain magnetic resonance imaging (MRI) volumes with postmortem brain pathology (both Alzheimer-related and cerebrovascular) in a community-derived cohort from the Framingham Heart Study. Participants (n=59) from the Framingham Heart Study were included if they were enrolled in the brain autopsy program and underwent antemortem clinical evaluation, neuropsychological testing, and brain MRI. Cortical neurofibrillary tangle pathology correlated with lower total cerebral brain (β±SE=-0.04±0.01, P=0.004) and hippocampal volumes (β±SE=-0.03±0.02, P=0.044) and larger temporal horns (log-transformed, β±SE=0.05±0.01, P=0.001). Similar findings were seen between total/cortical neuritic plaques and total cerebral brain and temporal horn volume. White matter hyperintensities (also log-transformed) were best predicted by the presence of deep nuclei microinfarcts (β±SE=0.53±0.21, P=0.016), whereas hippocampal volume was significantly decreased in the presence of hippocampal sclerosis (β±SE=-1.23±0.30, P<0.001). This study showed that volumetric MRI measures correlated with postmortem Alzheimer-related and cerebrovascular neuropathology in this community-derived cohort, confirming that these MRI measures are important antemortem surrogates for these dementia-related pathologies.

Plasma amyloid-β and risk of Alzheimer's disease in the Framingham Heart Study

BACKGROUND

Plasma amyloid-β (Aβ) peptide levels have been examined as a low-cost accessible marker for risk of incident Alzheimer's disease (AD) and dementia, but results have varied between studies. We reassessed these associations in one of the largest, prospective, community-based studies to date.

METHODS

A total of 2189 dementia-free, Framingham Study participants aged >60 years (mean age, 72 ± 8 years; 56% women) had plasma Aβ1-42 and Aβ1-40 measured and were followed prospectively (mean, 7.6 ± 3.0 years) for dementia/AD.

RESULTS

Increased plasma Aβ1-42 levels were associated with lower risk of dementia (Aβ1-42: hazard ratio [HR] = 0.80 [0.71‒0.90], P < .001; Aβ1-42-to-Aβ1-40 ratio: HR = 0.86 [0.76‒0.98], P = .027) and AD (Aβ1-42: HR = 0.79 [0.69‒0.90], P < .001; Aβ1-42-to-Aβ1-40 ratio: HR = 0.83 [0.72‒0.96], P = .012).

CONCLUSION

Our results suggest that lower plasma Aβ levels are associated with risk of incident AD and dementia. They encourage further evaluation of plasma Aβ levels as a biomarker for risk of developing clinical AD and dementia.

Aggregate effects of vascular risk factors on cerebrovascular changes in autopsy-confirmed Alzheimer's disease

We examined the relationships of antemortem vascular risk factors to postmortem cerebrovascular and Alzheimer's disease (AD) pathologies. Eighty-four AD patients underwent an assessment of vascular risk (blood pressure, cholesterol, smoking, cardiovascular disease, diabetes, atrial fibrillation, transient ischemic attack [TIA], or stroke) and later underwent brain autopsy. Given our aim to examine mild cerebrovascular changes (CVCs), individuals were excluded if autopsy revealed large stroke. The most common forms of CVC were circle of Willis atherosclerosis followed by arteriosclerosis, lacunes, and microinfarcts. Excluding the history of TIA/clinical stroke, individual vascular risk factors were not associated with CVC. However, the presence of multiple vascular risk factors was associated with CVC. Furthermore, the presence of CVC was associated with lower Braak and Braak stage. These findings highlight the importance of aggregate risk in the vascular contribution to dementia. Interventions designed to maintain cerebrovascular health may represent important opportunities for preventing or delaying dementia, even when AD is the dominant pathology.

Building a pipeline to discover and validate novel therapeutic targets and lead compounds for Alzheimer's disease

Cognitive decline, Alzheimer's disease (AD) and other causes are major public health problems worldwide. With changing demographics, the number of persons with dementia will increase rapidly. The treatment and prevention of AD and other dementias, therefore, is an urgent unmet need. There have been considerable advances in understanding the biology of many age-related disorders that cause dementia. Gains in understanding AD have led to the development of ante-mortem biomarkers of traditional neuropathology and the conduct of several phase III interventions in the amyloid-β cascade early in the disease process. Many other intervention strategies are in various stages of development. However, efforts to date have met with limited success. A recent National Institute on Aging Research Summit led to a number of requests for applications. One was to establish multi-disciplinary teams of investigators who use systems biology approaches and stem cell technology to identify a new generation of AD targets. We were recently awarded one of three such grants to build a pipeline that integrates epidemiology, systems biology, and stem cell technology to discover and validate novel therapeutic targets and lead compounds for AD treatment and prevention. Here we describe the two cohorts that provide the data and biospecimens being exploited for our pipeline and describe the available unique datasets. Second, we present evidence in support of a chronic disease model of AD that informs our choice of phenotypes as the target outcome. Third, we provide an overview of our approach. Finally, we present the details of our planned drug discovery pipeline.

Chronic traumatic encephalopathy: a spectrum of neuropathological changes following repetitive brain trauma in athletes and military personnel

Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease that occurs in association with repetitive traumatic brain injury experienced in sport and military service. In most instances, the clinical symptoms of the disease begin after a long period of latency ranging from several years to several decades. The initial symptoms are typically insidious, consisting of irritability, impulsivity, aggression, depression, short-term memory loss and heightened suicidality. The symptoms progress slowly over decades to include cognitive deficits and dementia. The pathology of CTE is characterized by the accumulation of phosphorylated tau protein in neurons and astrocytes in a pattern that is unique from other tauopathies, including Alzheimer’s disease. The hyperphosphorylated tau abnormalities begin focally, as perivascular neurofibrillary tangles and neurites at the depths of the cerebral sulci, and then spread to involve superficial layers of adjacent cortex before becoming a widespread degeneration affecting medial temporal lobe structures, diencephalon and brainstem. Most instances of CTE (>85% of cases) show abnormal accumulations of phosphorylated 43 kDa TAR DNA binding protein that are partially colocalized with phosphorylated tau protein. As CTE is characterized pathologically by frontal and temporal lobe atrophy, by abnormal deposits of phosphorylated tau and by 43 kDa TAR DNA binding protein and is associated clinically with behavioral and personality changes, as well as cognitive impairments, CTE is increasingly categorized as an acquired frontotemporal lobar degeneration. Currently, some of the greatest challenges are that CTE cannot be diagnosed during life and the incidence and prevalence of the disorder remain uncertain. Furthermore, the contribution of age, gender, genetics, stress, alcohol and substance abuse to the development of CTE remains to be determined.

The neuropathology of sport

The benefits of regular exercise, physical fitness and sports participation on cardiovascular and brain health are undeniable. Physical activity reduces the risk for cardiovascular disease, type 2 diabetes, hypertension, obesity, and stroke, and produces beneficial effects on cholesterol levels, antioxidant systems, inflammation, and vascular function. Exercise also enhances psychological health, reduces age-related loss of brain volume, improves cognition, reduces the risk of developing dementia, and impedes neurodegeneration. Nonetheless, the play of sports is associated with risks, including a risk for mild TBI (mTBI) and, rarely, catastrophic traumatic injury and death. There is also growing awareness that repetitive mTBIs, such as concussion and subconcussion, can occasionally produce persistent cognitive, behavioral, and psychiatric problems as well as lead to the development of a neurodegeneration, chronic traumatic encephalopathy (CTE). In this review, we summarize the beneficial aspects of sports participation on psychological, emotional, physical and cognitive health, and specifically analyze some of the less common adverse neuropathological outcomes, including concussion, second-impact syndrome, juvenile head trauma syndrome, catastrophic sudden death, and CTE. CTE is a latent neurodegeneration clinically associated with behavioral changes, executive dysfunction and cognitive impairments, and pathologically characterized by frontal and temporal lobe atrophy, neuronal and axonal loss, and abnormal deposits of paired helical filament (PHF)-tau and 43 kDa TAR deoxyribonucleic acid (DNA)-binding protein (TDP-43). CTE often occurs as a sole diagnosis, but may be associated with other neurodegenerative disorders, including motor neuron disease (CTE-MND). Although the incidence and prevalence of CTE are not known, CTE has been reported most frequently in American football players and boxers. Other sports associated with CTE include ice hockey, professional wrestling, soccer, rugby, and baseball.

Chronic traumatic encephalopathy in sport: a systematic review

OBJECTIVE

To provide a critical review of chronic traumatic encephalopathy (CTE) by considering the range of clinical presentations, neuropathology and the strength of evidence for CTE as a distinct syndrome.

DATA SOURCES

Seven electronic databases were searched using a combination of MeSH terms and key words to identify relevant articles.

REVIEW METHODS

Specific inclusion and exclusion criteria were used to select studies for review. Data extracted where present included study population, exposure/outcome measures, clinical data, neurological examination findings, cognitive assessment, investigation results and neuropathology results.

RESULTS

The data from 158 published case studies were reviewed. Critical differences between the older descriptions of CTE (the 'classic' syndrome) and the recent descriptions (the 'modern' syndrome) exist in the age of onset, natural history, clinical features, pathological findings and diagnostic criteria, which suggests that modern CTE is a different syndrome. The methodology of the current studies does not allow determination of aetiology or risk factors.

CONCLUSIONS

The clinicopathological differences between the 'classic' CTE syndrome and the 'modern' syndrome suggest that the new syndrome needs a different nomenclature. Further research is required to clearly define the clinical phenotype of the modern CTE syndrome and establish the underlying aetiology. Future research needs to address these issues through large-scale, prospective clinicopathological studies.

Increased expression of TrkB and Capzb2 accompanies preserved cognitive status in early Alzheimer disease pathology

Brain-derived neurotrophic factor (BDNF) and its receptor tyrosine kinase B (TrkB) may influence brain reserve, the ability of the brain to tolerate pathological changes without significant decline in function. Here, we explore whether a specifically vulnerable population of human neurons shows a compensatory response to the neuropathological changes of Alzheimer disease (AD) and whether that response depends on an upregulation of the BDNF pathway. We observed increased neuronal TrkB expression associated with early-stage AD pathology (Braak and Braak stages I-II) in hippocampal CA1 region samples from cognitively intact Framingham Heart Study subjects (n = 5) when compared with cognitively intact individuals with no neurofibrillary tangles (n = 4). Because BDNF/TrkB signaling affects memory formation and retention through modification of the actin cytoskeleton, we examined the expression of actin capping protein β2 (Capzb2), a marker of actin cytoskeleton reorganization. Capzb2 expression was also significantly increased in CA1 hippocampal neurons of cognitively intact subjects with early-stage AD pathology. Our data suggest that increased expression of TrkB and Capzb2 accompanies adequate brain reserve in the initial stages of AD pathology. In subsequent stages of AD, the higher levels of TrkB and Capzb2 expression achieved may not be sufficient to prevent cognitive decline.