To examine the relationship between plasma lipid measurements and incident ischemic vascular events (ischemic stroke [IS], and as a positive control, myocardial infarction [MI]) in a community cohort.
In 6,276 stroke-free Framingham participants (aged 64 ± 10 years, 56% female), we related plasma lipid levels (total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], and TC/HDL-C ratio) measured at the original cohort 15th (1977–1979) and 20th examination cycles (1986–1990) and (TC, HDL-C, TC/HDL-C ratio, triglycerides [TG], and low-density lipoprotein cholesterol [LDL-C]) measured at the offspring fourth examination (1995–1998), to 10-year risk of incident IS and MI. Utilizing genome-wide genotyping in the same subjects, we used mendelian randomization methods to assess whether observed associations were incidental or causal.
During a mean follow-up of 9 years, 301 participants experienced incident IS. In multivariable-adjusted analyses, HDL-C ≤40 mg/dL and TC/HDL ratio ≥5 were associated with increased risk of IS (hazard ratio [95% confidence interval]: 1.59 [1.23–2.05], p < 0.001 and 1.47 [1.15–1.87], p < 0.001), but not TC or LDL-C. In adjusted analysis, a strong association between TG and IS was diminished. In the MI-free sample (n = 5,875, aged 64 ± 10 years, 58% female; 403 MI events), all lipid markers were associated with MI risk. A genetic risk score comprising 47 known determinants of circulating HDL-C was not associated with IS.
In a middle-aged to elderly community sample, we observed that low HDL-C and high TC/HDL-C ratio, but not LDL-C or TG were associated with risk of incident IS. We observed the usual associations between lipids and risk of MI. Our findings suggest an important, but less likely causal, role of HDL-C over other lipid biomarkers for optimal stroke risk stratification.
Parkinson disease (PD) is the second most common neurodegenerative disorder. Its diagnosis relies solely on a clinical examination and is not straightforward because no diagnostic test exists. Large, population-based, prospective cohort studies designed to examine other outcomes that are more common than PD might provide cost-efficient alternatives for studying the disease. However, most cohort studies have not implemented rigorous systematic screening for PD. A majority of epidemiologic studies that utilize population-based prospective designs rely on secondary data sources to identify PD cases. Direct validation of these secondary sources against clinical diagnostic criteria is lacking. The Framingham Heart Study has prospectively screened and evaluated participants for PD based on clinical diagnostic criteria. We assessed the predictive value of secondary sources for PD identification relative to clinical diagnostic criteria in the Framingham Heart Study (2001–2012). We found positive predictive values of 1.0 (95% confidence interval: 0.868, 1.0), 1.0 (95% confidence interval: 0.839, 1.0), and 0.50 (95% confidence interval: 0.307, 0.694) for PD identified from self-report, use of antiparkinsonian medications, and Medicare claims, respectively. The negative predictive values were all higher than 0.99. Our results highlight the limitations of using only Medicare claims data and suggest that population-based cohorts may be utilized for the study of PD determined via self-report or medication inventories while preserving a high degree of confidence in the validity of PD case identification.
case ascertainment; International Classification of Diseases; Parkinson disease; validation studies
Detection of “any cognitive impairment” is mandated as part of the Medicare annual wellness visit, but screening all patients may result in excessive false positives.
We developed and validated a brief Dementia Screening Indicator using data from four large, ongoing cohort studies (the Cardiovascular Health Study [CHS]; the Framingham Heart Study [FHS]; the Health and Retirement Study [HRS]; the Sacramento Area Latino Study on Aging [SALSA]) to help clinicians identify a subgroup of high-risk patients to target for cognitive screening.
The final Dementia Screening Indicator included age (1 point/year; ages, 65–79 years), less than 12 years of education (9 points), stroke (6 points), diabetes mellitus (3 points), body mass index less than 18.5 kg/m2 (8 points), requiring assistance with money or medications (10 points), and depressive symptoms (6 points). Accuracy was good across the cohorts (Harrell’s C statistic: CHS, 0.68; FHS, 0.77; HRS, 0.76; SALSA, 0.78).
The Dementia Screening Indicator is a simple tool that may be useful in primary care settings to identify high-risk patients to target for cognitive screening.
Dementia; Screening; Risk prediction modeling; Primary care
Individuals with a high risk of stroke are also more prone to cognitive impairment perhaps due to concomitant vascular risk factors. In addition, clinical stroke increases the risk of subsequent dementia. Nevertheless, the relationship between clinical stroke and subsequent cognitive function in initially non-demented individuals remains less clear as most prior studies examined case series without controls.
To specify among non-demented individuals the cognitive domains affected by clinical stroke, independently of vascular risk factors and pre-stroke cognition.
One hundred-thirty-two Framingham Study participants (mean age=77±9 years, 54% women) with prospectively validated initial strokes, as well as age- and sex-matched controls, underwent identical cognitive evaluations ~6 months after the stroke. Linear regression models were used to assess the differences in cognitive scores between stroke cases and controls adjusting for pre-stroke cognitive function as assessed by Mini-Mental State Examination scores, and with and without adjustment for vascular risk factors.
Adjusting for pre-stroke cognition and vascular risk factors, persons with stroke had poorer cognitive function in the domains of immediate recall of logical and visual memories (β=−1.27±0.60; P=0.035, β=−1.03±0.47; P=0.028, respectively), verbal learning (paired associate test; β=−1.31±0.57; P=0.023), language (Boston naming test; β=−0.27±0.08; P=0.002), executive function (Digit span backwards; β=−0.53±0.21; P=0.015) and visuo-spatial and motor skills (block design; β=−3.02±1.06; P=0.005).
Clinical stroke is associated with subsequent poorer performance in multiple cognitive domains. This association cannot be entirely explained by the individual’s cognitive function prior to stroke or by concomitant vascular risk factor levels.
cerebrovascular disease; stroke related outcomes; cognitive function; vascular risk factors; neuropsychology matched cohort study
Studies of clinical and community cohorts have shown that antemortem imaging measures of hippocampal volume have correlated with postmortem Alzheimer's pathology. Fewer studies have examined the relationship between both Alzheimer's 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 (FHS). Participants (n=59) from the FHS 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 (beta±SE=−0.04±0.01, p=0.004) and hippocampal volumes (beta±SE=−0.03±0.02, p=0.044) and larger temporal horns (log-transformed, beta±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 (beta±SE=0.53±0.21, p=0.016), whereas hippocampal volume was significantly decreased in the presence of hippocampal sclerosis (beta±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.
To relate serum insulin-like growth factor-1 (IGF-1) to risk of Alzheimer disease (AD) dementia and to brain volumes in a dementia-free community sample spanning middle and older ages.
Dementia-free Framingham participants from generation 1 (n = 789, age 79 ± 4 years, 64% women) and generation 2 (n = 2,793, age 61 ± 9 years, 55% women; total = 3,582, age 65 ± 11 years, 57% women) had serum IGF-1 measured in 1990–1994 and 1998–2001, respectively, and were followed prospectively for incident dementia and AD dementia. Brain MRI was obtained in stroke- and dementia-free survivors of both generations 1 (n = 186) and 2 (n = 1,867) during 1999–2005. Baseline IGF-1 was related to risk of incident dementia using Cox models and to total brain and hippocampal volumes using linear regression in multivariable models adjusted for age, sex, APOE ε4, plasma homocysteine, waist-hip ratio, and physical activity.
Mean IGF-1 levels were 144 ± 60 μg/L in generation 1 and 114 ± 37 μg/L in generation 2. We observed 279 cases of incident dementia (230 AD dementia) over a mean follow-up of 7.4 ± 3.1 years. Persons with IGF-1 in the lowest quartile had a 51% greater risk of AD dementia (hazard ratio = 1.51, 95% confidence interval: 1.14–2.00; p = 0.004). Among persons without dementia, higher IGF-1 levels were associated with greater total brain volumes (β/SD increment in IGF-1 was 0.55 ± 0.24, p = 0.025; and 0.26 ± 0.06, p < 0.001, for generations 1 and 2, respectively).
Lower serum levels of IGF-1 are associated with an increased risk of developing AD dementia and higher levels with greater brain volumes even among middle-aged community-dwelling participants free of stroke and dementia. Higher levels of IGF-1 may protect against subclinical and clinical neurodegeneration.
Background: offspring of long-lived individuals have lower risk for dementia. We examined the relation between parental longevity and cognition and subclinical markers of brain ageing in community-dwelling adult offspring.
Methods: offspring participants with both parents in the Framingham Heart Study, aged ≥55 years and dementia-free underwent baseline and repeat neuropsychological (NP) testing and brain magnetic resonance imaging (MRI). Parental longevity was defined as having at least one parent survive to age ≥85 years. To test the association between parental longevity and measures of cognition and brain volumes, we used multivariable linear and logistic regression adjusting for age, sex, education and time to NP testing or brain MRI.
Results: of 728 offspring (mean age 66 years, 54% women), 407 (56%) had ≥1 parent achieve longevity. In cross-sectional analysis, parental longevity was associated with better scores on attention (beta 0.21 ± 0.08, P = 0.006) and a lower odds of extensive white matter hyperintensity on brain MRI (odds ratio 0.59, 95% CI: 0.38, 0.92, P = 0.019). The association with white matter hyperintensity was no longer significant in models adjusted for cardiovascular risk factors and disease. In longitudinal analysis (6.7 ± 1.7 years later), offspring with parental longevity had slower decline in attention (0.18 ± 0.08, P = 0.038), executive function (beta 0.19 ± 0.09, P = 0.031) and visual memory (beta −0.18 ± 0.08, P = 0.023), and less increase in temporal horn volume (beta −0.25 ± 0.09, P = 0.005). The associations persisted in fully adjusted models.
Conclusion: parental longevity is associated with better brain ageing in middle-aged offspring.
brain ageing; brain imaging; cognition; longevity; neuropsychological testing; older people; parental longevity
Background and purpose
Cerebral microbleeds (CMBs) are associated with increased risk of stroke and poor cognition. Vascular risk factors and medications used for stroke prevention may increase the risk of CMB. We examined the prevalence of CMB and the association of these risk factors with CMB, postulating that risk factors for cerebral amyloid angiopathy would be associated with lobar CMB and markers of hypertensive vasculopathy with deep CMB.
We include 1,965 Framingham Original and Offspring participants (age 66.5±11.0years; 54%women) and evaluated the age- and sex-specific prevalence of CMB. We related various vascular and genetic (APOE) risk factors and medication use to presence of CMB overall and stratified by brain location (deep, lobar or mixed).
CMBs were observed in 8.8% of participants, being mostly lobar (63%). CMB prevalence increased with age (p<0.0001) and was higher in men (p<0.001). Hypertension increased risk of any CMB, and in deep and mixed locations (p<0.05), and low total cholesterol and APOE ε4 increased risk of lobar CMB (p<0.05). Statin use increased risk of lobar and mixed location CMB (p<0.05). The latter association was not affected by adjustment for cholesterol levels, or concomitant medication use.
We observed the expected association of hypertension with deep CMB and low cholesterol and APOEε4 with lobar CMB. Additionally, statin use was independently associated with CMB risk. This potential adverse effect of statin use needs to be examined in other cohorts.
Brain‐derived neurotrophic factor (BDNF) is a pleiotropic peptide involved in maintaining
endothelial integrity. It is unknown if circulating BDNF levels are associated with risk of
cardiovascular disease (CVD).
Methods and Results
We prospectively investigated the association of circulating BDNF levels with cardiovascular
events and mortality in 3687 participants (mean age 65 years, 2068 women) from the Framingham Heart
Study (FHS). Using a common nonsynonomous single nucleotide polymorphism (SNP) in the
BDNF gene (rs6265), we then performed a Mendelian randomization experiment in the
CARDIoGRAM (Coronary ARtery DIsease Genome‐Wide Replication And Meta‐Analysis)
consortium (>22 000 coronary artery disease [CAD] cases, >60 000 controls) to
investigate whether SNP rs6265 was associated with CAD in CARDIoGRAM and, if so, whether the effect
estimate differed from that predicted based on FHS data. On follow‐up (median 8.9 years), 467
individuals (261 women) in FHS experienced a CVD event, and 835 (430 women) died. In
multivariable‐adjusted Cox regression, serum BDNF was associated inversely with CVD risk
(hazard ratio [HR] per 1‐SD increase 0.88, 95% CI 0.80 to 0.97,
P=0.01) and with mortality (HR 0.87, 95% CI 0.80 to 0.93,
P=0.0002). SNP rs6265 was associated with BDNF concentrations (0.772
ng/mL increase per minor allele copy) in FHS. In CARDIoGRAM, SNP rs6265 was associated with
CAD (odds ratio 0.957, 95% CI 0.923 to 0.992), a magnitude consistent with the predicted
effect (HR per minor allele copy 0.99, 95% CI 0.98 to 1.0; P=0.06 for
difference between predicted and observed effect).
Higher serum BDNF is associated with a decreased risk of CVD and mortality. Mendelian
randomization suggests a causal protective role of BDNF in the pathogenesis of CVD.
cardiovascular disease; growth factors; Mendelian randomization; mortality; risk factors
Novel error scores and traditional indices of executive function (EF) were related to cardiovascular risk factors (CVRF) measured 10–15 years earlier.
From 1991–1995, the Framingham Stroke Risk Profile (FSRP), a composite score of cardiovascular risk, was ascertained in 1755 Framingham Offspring participants (54% women, mean age= 54 ± 9 years). Participants were administered EF tests: FAS and Animals Fluency tests, Trail Making Test B (TrB), and Digit Span-Backwards (DS-B) in 2005–2009. Linear and logistic regression were used to relate the FSRP and its components to both error responses and traditional scores.
Consistent with previous findings, the FSRP and the individual components diabetes and sex were associated with several traditional measures of EF. Of interest were relationships between the FSRP score and TrB Total Errors (p=0.04), DS-B % Total Errors (p=0.02) and DS-B Capacity Score (p=0.03), and prevalent CVD related to making FAS Perseverations in the 75th percentile (p=0.03). By comparison, FSRP and CVD were not related to the traditional DS-B or FAS scores. Additionally, age was associated with higher Animals % Total Errors and % Perseverations among ApoE4+ individuals and with higher TrB Total Errors among ApoE4− individuals.
For those middle-aged and healthy, including those ApoE4+, CVRF are related to impairments in EF as ascertained by novel errors as well as traditional measures.
Neuropsychological assessment; Executive function; Mild cognitive impairment; ApolipoproteinE allele 4
Vascular risk factors have been associated with cognitive decline, however, it remains unclear whether apolipoprotein E (APOE) genotype modifies this relationship. We aimed to further elucidate these relationships and extend previous findings by examining data from a more comprehensive cognitive assessment than used in prior studies. 1,436 participants from the prospective Framingham Offspring Cohort Study underwent health examination from 1991-1995, followed by a baseline neuropsychological assessment (1999-2003) and a repeat neuropsychological assessment approximately eight years later (2004-2009). Multivariate linear regression analyses were performed to examine the relationship between midlife vascular risk factors, presence of the APOE ε4 allele, and cognitive change. APOE genotype significantly modified the associations between both midlife hypertension and cardiovascular disease and decline in language abilities as well as midlife diabetes and decline in verbal memory, attention, and visuospatial abilities. Associations between increased midlife vascular risk burden and greater cognitive decline were observed among APOE ε4 carriers but not non-carriers. The present findings revealed a subgroup at increased risk for cognitive decline (APOE ε4 carriers with midlife exposure to vascular risk factors) and suggest that treatment of vascular risk factors during midlife may reduce the risk of cognitive impairment later in life, particularly among APOE ε4 carriers.
Apolipoprotein E; Cognition; Vascular Risk; Aging; Diabetes; Hypertension; Cardiovascular Disease
Psychometric definitions of mild cognitive impairment (MCI) typically use cut-off levels set at 1.5 standard deviations below age- and education-adjusted norms, assuming that the education adjustment accounts for premorbid abilities. However, non-cognitive factors impact educational attainment, potentially leading to incorrect categorization as MCI. We examined whether using an adjustment based on reading performance (Wide Range Achievement Test [WRAT] Reading) improved MCI diagnostic accuracy.
935 Framingham Offspring (mean age 72 ± 5) underwent tests of Memory, Executive Function, Abstraction, Language, and Visuospatial Function as part of a neuropsychological test battery. Domain-specific test scores were regressed onto age and WRAT score, or education, to define MCI. Survival analyses were used to relate baseline MCI to incident dementia.
The two MCI definitions differed most for the lowest and highest education groups. The WRAT definition was more strongly associated with incident dementia for all five tests. MCI-level Abstraction performance was associated with incident dementia using the WRAT definition (HR = 3.20, p = .033), but not the education definition (HR = 1.19, p = .814).
The WRAT should be considered along with the standard measure of years of education, as it may be a better surrogate marker of premorbid abilities.
Mild cognitive impairment; premorbid abilities; neuropsychological assessment; Alzheimer's disease; longitudinal
Background and Purpose
BDNF, a major neurotrophin and VEGF, an endothelial growth factor have a documented role in neurogenesis, angiogenesis and neuronal survival. In animal experiments they impact infarct size and functional motor recovery after an ischemic brain lesion. We sought to examine the association of serum BDNF and VEGF with the risk of clinical stroke or subclinical vascular brain injury in a community-based sample.
In 3440 stroke/TIA-free FHS participants (mean age 65±11yrs, 56%W), we related baseline BDNF and logVEGF to risk of incident stroke/TIA. In a subsample with brain MRI and with neuropsychological (NP) tests available (N=1863 and 2104, respectively; mean age 61±9yrs, 55%W, in each) we related baseline BDNF and logVEGF to log-white matter hyperintensity volume (lWMHV) on brain MRI, and to visuospatial memory and executive function tests.
During a median follow-up of 10 years, 193 participants experienced incident stroke/TIA. In multivariable analyses adjusted for age-, sex- and traditional stroke risk factors, lower BDNF and higher logVEGF levels were associated with an increased risk of incident stroke/TIA (HR comparing BDNF Q1 versus Q2–4:1.47, 95%CI:1.09–2.00, p=0.012; and HR/SD increase in logVEGF:1.21, 95%CI:1.04–1.40, p=0.012). Persons with higher BDNF levels had less lWMHV (β±SE=−0.05±0.02; p=0.025), and better visual memory (β±SE=0.18±0.07; p=0.005).
Lower serum BDNF and higher VEGF concentrations were associated with increased risk of incident stroke/TIA. Higher levels of BDNF were also associated with less white matter hyperintensity and better visual memory. Our findings suggest that circulating BDNF and VEGF levels modify risk of clinical and subclinical vascular brain injury.
BDNF; VEGF; Risk; Stroke; Brain MRI; Subclinical
Background and purpose
Exposure to vascular risk factors has a gradual deleterious effect on brain MRI and cognitive measures. We explored whether a pattern of these measures exists that predicts stroke and Alzheimer’s disease (AD) risk.
A cognitive battery was administered to 1,679 dementia and stroke-free Framingham Offspring (age>55; mean=65.7±7.0) between 1999 and 2004; participants were also free of other neurological conditions that could affect cognition and >90% also had brain MRI examination. We related cognitive and MRI measures to risks of incident stroke and AD during up to 10 years of follow-up. As a secondary analysis, we explored these associations in the FHS Original cohort (mean age 67.5±7.3 and 84.8±3.3 at the cognitive assessment and MRI examination, respectively).
A total of 55 Offspring participants sustained strokes and 31 developed AD. Offspring who scored <1.5 standard-deviations below predicted mean scores, for age and education, on an executive function test, had a higher risk of future stroke (HR=2.27;95%CI:1.06–4.85) and AD (3.60;95%CI:1.52–8.52); additional cognitive tests also predicted AD. Participants with low (<20%ile) total brain volume and high (>20%ile) white matter hyperintensity volume had a higher risk of stroke (HR=1.97;95%CI:1.03–3.77 and HR=2.74;95%CI:1.51–5.00, respectively) but not AD. Hippocampal volume at the bottom quintile predicted AD in the Offspring and Original cohorts (HR=4.41;95%CI:2.00–9.72 and HR=2.37;95%CI:1.12–5.00, respectively). A stepwise increase in stroke risk was apparent with increasing numbers of these cognitive and imagingmarkers.
Specific patterns of cognitive and brain structural measures observed even in early aging predict stroke risk and may serve as biomarkers for risk prediction.
stroke; Alzheimer’s disease; cognitive function; brain MRI
To determine the association of arterial stiffness and pressure pulsatility, which can damage small vessels in the brain, with vascular and Alzheimer-type brain aging.
Stroke- and dementia-free Framingham Offspring Study participants (n = 1,587, 61 ± 9 years, 45% male) underwent study of tonometric arterial stiffness and endothelial function (1998–2001) and brain MRI and cognition (1999–2002). We related carotid-femoral pulse wave velocity (CFPWV), mean arterial and central pulse pressure, and endothelial function to vascular brain aging by MRI (total cerebral brain volume [TCBV], white matter hyperintensity volume, silent cerebral infarcts) and vascular and Alzheimer-type cognitive aging (Trails B minus Trails A and logical memory-delayed recall, respectively).
Higher CFPWV was associated with lower TCBV, greater white matter hyperintensity volume, and greater prevalence of silent cerebral infarcts (all p < 0.05). Each SD greater CFPWV was associated with lower TCBV equivalent to 1.2 years of brain aging. Mean arterial and central pulse pressure were associated with greater white matter hyperintensity volume (p = 0.005) and lower TCBV (p = 0.02), respectively, and worse verbal memory (both p < 0.05). Associations of tonometry variables with TCBV and white matter hyperintensity volume were stronger among those aged 65 years and older vs those younger than 65 years (p < 0.10 for interaction). Brachial artery endothelial function was unrelated to MRI measures (all p > 0.05).
Greater arterial stiffness and pressure pulsatility are associated with brain aging, MRI vascular insults, and memory deficits typically seen in Alzheimer dementia. Future investigations are warranted to evaluate the potential impact of prevention and treatment of unfavorable arterial hemodynamics on neurocognitive outcomes.
We aimed to examine the association of APOE ε genotype with MRI markers of cerebrovascular disease (CVD): white matter hyperintensities, brain infarcts, and cerebral microbleeds.
We performed a systematic review and meta-analysis of 42 cross-sectional or longitudinal studies identified in PubMed from 1966 to June 2012 (n = 29,965). This included unpublished data from 3 population-based studies: 3C-Dijon, Framingham Heart Study, and Sydney Memory and Ageing Study. When necessary, authors were contacted to provide effect estimates for the meta-analysis.
APOE ε4 carrier status and APOE ε44 genotype were associated with increasing white matter hyperintensity burden (sample size–weighted z score meta-analysis [meta]-p = 0.0034 and 0.0030) and presence of cerebral microbleeds (meta odds ratio [OR] = 1.24, 95% confidence interval [CI] [1.07, 1.43], p = 0.004, and 1.87 [1.26, 2.78], p = 0.002), especially lobar. APOE ε2 carrier status was associated with increasing white matter hyperintensity load (z score meta-p = 0.00053) and risk of brain infarct (meta OR = 1.41[1.09, 1.81], p = 0.008).
APOE ε4 and APOE ε2 were associated with increasing burden in MRI markers for both hemorrhagic and ischemic CVD. While the association of APOE ε4 with an increased burden of CVD could be partly contributing to the relationship between APOE ε4 and AD, APOE ε2 was associated with MRI markers of CVD in the opposite direction compared to AD.
We examined the progression of lexical-retrieval deficits in individuals with neuropathologically determined Alzheimer's disease (AD; n = 23) and a comparison group without criteria for AD (n = 24) to determine whether linguistic changes were a significant marker of the disease. Our participants underwent multiple administrations of a neuropsychological battery, with initial administration occurring on average 16 years prior to death. The battery included the Boston Naming Test (BNT), a letter fluency task (FAS), and written description of the Cookie Theft Picture (CTP).
Repeated measures analysis revealed that the AD-group showed progressively greater decline in FAS and CTP lexical performance than the comparison group. Cross-sectional time-specific group comparisons indicated that the CTP differentiated performance between the two groups at 7–9 years prior to death and FAS and BNT only at 2–4 years. These results suggest that lexical-retrieval deficits in written discourse serve as an early indicator of AD.
discourse; naming; early markers; neuropathology; Alzheimer's disease
In animal studies, brain-derived neurotrophic factor (BDNF) has been shown to impact neuronal survival and function and improve synaptic plasticity and long-term memory. Circulating BDNF levels increase with physical activity and caloric restriction, thus BDNF may mediate some of the observed associations between lifestyle and the risk for dementia. Some prior studies showed lower circulating BDNF in persons with Alzheimer disease (AD) compared with control participants; however, it remains uncertain whether reduced levels precede dementia onset.
To examine whether higher serum BDNF levels in cognitively healthy adults protect against the future risk for dementia and AD and to identify potential modifiers of this association.
DESIGN, SETTING, AND PARTICIPANTS
Framingham Study original and offspring participants were followed up from 1992 and 1998, respectively, for up to 10 years. We used Cox models to relate BDNF levels to the risk for dementia and AD and adjusted for potential confounders. We also ran sensitivity analyses stratified by sex, age, and education, as well as related BDNF genetic variants to AD risk. This community-based, prospective cohort study involved 2131 dementia-free participants aged 60 years and older (mean [SD] age, 72  years; 56% women).
MAIN OUTCOMES AND MEASURES
Ten-year incidence of dementia and AD.
During follow-up, 140 participants developed dementia, 117 of whom had AD. Controlling for age and sex, each standard-deviation increment in BDNF was associated with a 33% lower risk for dementia and AD (P = .006 and P = .01, respectively) and these associations persisted after additional adjustments. Compared with the bottom quintile, BDNF levels in the top quintile were associated with less than half the risk for dementia and AD (hazard ratio, 0.49; 95%CI, 0.28–0.85; P = .01; and hazard ratio, 0.46; 95%CI, 0.24–0.86; P = .02, respectively). These associations were apparent only among women, persons aged 80 years and older, and those with college degrees (hazard ratios for AD: 0.65, [95%CI, 0.50–0.85], P = .001; 0.63 [95%CI, 0.47–0.85], P = .002; and 0.27 [95%CI, 0.11–0.65], P = .003, respectively). Brain-derived neurotrophic factor genetic variants were not associated with AD risk.
CONCLUSIONS AND RELEVANCE
Higher serum BDNF levels may protect against future occurrence of dementia and AD. Our findings suggest a role for BDNF in the biology and possibly in the prevention of dementia and AD, especially in select subgroups of women and older and more highly educated persons.
Circulating homocysteine levels (tHcy), a product of the folate one carbon metabolism pathway (FOCM) through the demethylation of methionine, are heritable and are associated with an increased risk of common diseases such as stroke, cardiovascular disease (CVD), cancer and dementia. The FOCM is the sole source of de novo methyl group synthesis, impacting many biological and epigenetic pathways. However, the genetic determinants of elevated tHcy (hyperhomocysteinemia), dysregulation of methionine metabolism and the underlying biological processes remain unclear. We conducted independent genome-wide association studies and a meta-analysis of methionine metabolism, characterized by post-methionine load test tHcy, in 2,710 participants from the Framingham Heart Study (FHS) and 2,100 participants from the Vitamin Intervention for Stroke Prevention (VISP) clinical trial, and then examined the association of the identified loci with incident stroke in FHS. Five genes in the FOCM pathway (GNMT [p = 1.60×10−63], CBS [p = 3.15×10−26], CPS1 [p = 9.10×10−13], ALDH1L1 [p = 7.3×10−13] and PSPH [p = 1.17×10−16]) were strongly associated with the difference between pre- and post-methionine load test tHcy levels (ΔPOST). Of these, one variant in the ALDH1L1 locus, rs2364368, was associated with incident ischemic stroke. Promoter analyses reveal genetic and epigenetic differences that may explain a direct effect on GNMT transcription and a downstream affect on methionine metabolism. Additionally, a genetic-score consisting of the five significant loci explains 13% of the variance of ΔPOST in FHS and 6% of the variance in VISP. Association between variants in FOCM genes with ΔPOST suggest novel mechanisms that lead to differences in methionine metabolism, and possibly the epigenome, impacting disease risk. These data emphasize the importance of a concerted effort to understand regulators of one carbon metabolism as potential therapeutic targets.
Elevated homocysteine (tHcy) is strongly associated with risk for common disorders such as stroke, cardiovascular disease and Alzheimer disease. Lowering tHcy levels has proven to have variable success in reducing clinical risk, so the question remains, “Are we correctly targeting these disorders by lowering tHcy?” Understanding folate one-carbon metabolism pathway (FOCM) genetic variation will aid us in developing new targets for therapy. The FOCM is essential in regulation of the epigenome, which controls genes in ways beyond nucleotide sequence. We present data generated from stroke-only and general populations where we identify strong association of genetic risk factors for variation in one-carbon metabolism function, characterized by the post-methionine load test. We show that GNMT harbors genetic and epigenetic differences that influence gene function, which may have downstream effects on the epigenome of the cell, affecting disease risk. We developed a genetic risk score that predicts post-methionine load homocysteine levels that may be useful in clinic. Finally, we identified a novel association between ischemic stroke and ALDH1L1, which emphasizes the clinical importance of this work. Our results highlight the importance of a concerted effort to target the FOCM (beyond tHcy) and parallel pathways in future pharmacogenetic work using the genetic variation we describe here.
Background and purpose
Parental stroke has been related to an increased risk of stroke in the offspring. This study examines whether parental stroke is also associated with increased vascular brain injury and poorer cognitive performance among offspring free of clinical stroke.
Multivariable regression analyses were used to relate parental stroke to cross-sectional and change in brain magnetic resonance imaging measures and cognitive function among the offspring, with and without adjustment for vascular risk factors.
Stroke- and dementia-free Framingham Offspring (n=1,297, age:61±9 years, 54% women) were studied. Parental stroke by age 65 years was associated with a higher baseline white matter hyperintensity volume (WMHV;β=0.17±0.08; p=0.027), and with lower visual memory performance (β =−0.80±0.34; p=0.017). During a 6 year follow-up, parental stroke was also associated with increase in WMHV (odds ratio [OR] = 1.87;95%CI:1.03–3.38) and decline in executive function (Trails B–A; OR=1.81;95%CI:1.06–3.09). The associations with WMHV and visual memory attenuated after additional adjustment for concomitant vascular risk factors.
Parental stroke by age 65 years is associated with increased vascular brain injury and lower memory in offspring equivalent to 3 and 7 years of brain aging, respectively. This may be partly attributed to inheritance of vascular risk factors.
stroke; cognitive function; brain MRI
This study aimed to determine whether relationships between obesity, as measured by waist-to-hip ratio (WHR), and cognition and brain structure were modified by the apolipoprotein epsilon 4 allele (apoE4). The sample included 1,969 stroke and dementia-free participants from the Framingham Offspring Cohort who underwent neuropsychological (NP) testing and structural Magnetic Resonance Imaging (MRI) between 1999–2002. WHR was categorized into sex-specific quartiles with those in Q4 representing central obesity. Multivariate linear regression estimated the relationships between Q4-WHR, cognitive and MRI measures; interaction terms examined modification of these relationships by the presence of apoE4. All analyses were cross sectional.
ApoE4 status significantly modified a number of associations. Specifically, we observed a significant negative relationship between Q4-WHR and a measure of executive function in the apoE4+ group but not in the apoE4− group. Similarly, we observed a stronger negative relationship between Q4-WHR and a measure of memory function for those in the apoE4+ group compared to those in the apoE4− group. Additionally, apoE4 status modified the relationship between Q4-WHR and two measures of structural brain integrity. First, a paradoxical finding of a negative association between WHR and frontal brain volume that was significant only for those in the apoE4- group, and a second finding that WHR was significantly associated with greater white matter hyperintensity volume only in the apoE4+ group.
These findings suggest that associations between central adiposity and both neuropsychological performance and underlying brain structure are highly complex and must be considered in the context of possible modifying genetic influences.
waist-to-hip ratio; apoE4; metabolic syndrome; obesity; Alzheimer’s disease
Studies have found that executive functioning is affected early in the pathophysiological processes associated with Alzheimer’s disease and vascular dementia. There also exists a range of functioning on executive tasks during normal aging. Although qualitative data are commonly utilized in clinical practice for evaluating subtle changes in cognitive functioning and diagnostic discernment, it is not clear whether error responses used in clinical practice are also evident as normative behavior.
As part of an extensive battery of neuropsychological tests, executive functioning measures (i.e., Trail Making-B, Similarities and Verbal Fluency tests) were administered via standardized administration prescript. Regression analyses were used to determine associations between vascular aging indices and qualitative performance measures. Descriptive statistics are included for 1907 cognitively normal individuals.
Results suggest that while qualitative errors do occur, they are relatively infrequent within a presumably cognitively normal sample. Error commission rates on executive functioning tests are significantly associated with both age and education.
Provided is a baseline profile of errors committed on tests of executive function across a range of age and educational levels. The normative datasets are included, stratified by age and educational achievement, for which to compare qualitative test performance of clinical and research populations.
A large number of longitudinal studies of population-based ageing cohorts are in progress internationally, but the insights from these studies into the risk and protective factors for cognitive ageing and conditions like mild cognitive impairment and dementia have been inconsistent. Some of the problems confounding this research can be reduced by harmonising and pooling data across studies. COSMIC (Cohort Studies of Memory in an International Consortium) aims to harmonise data from international cohort studies of cognitive ageing, in order to better understand the determinants of cognitive ageing and neurocognitive disorders.
Longitudinal studies of cognitive ageing and dementia with at least 500 individuals aged 60 years or over are eligible and invited to be members of COSMIC. There are currently 17 member studies, from regions that include Asia, Australia, Europe, and North America. A Research Steering Committee has been established, two meetings of study leaders held, and a website developed. The initial attempts at harmonising key variables like neuropsychological test scores are in progress.
The challenges of international consortia like COSMIC include efficient communication among members, extended use of resources, and data harmonisation. Successful harmonisation will facilitate projects investigating rates of cognitive decline, risk and protective factors for mild cognitive impairment, and biomarkers of mild cognitive impairment and dementia. Extended implications of COSMIC could include standardised ways of collecting and reporting data, and a rich cognitive ageing database being made available to other researchers. COSMIC could potentially transform our understanding of the epidemiology of cognitive ageing, and have a world-wide impact on promoting successful ageing.
Cohort studies; Cognitive ageing; Data harmonisation; Dementia; International consortium; Mild cognitive impairment