Measures of brain morphology and infarction in the framingham heart study: establishing what is normal

Lesion Explorer: a comprehensive segmentation and parcellation package to obtain regional volumetrics for subcortical hyperintensities and intracranial tissue

Subcortical hyperintensities (SH) are a commonly observed phenomenon on MRI of the aging brain (Kertesz et al., 1988). Conflicting behavioral, cognitive and pathological associations reported in the literature underline the need to develop an intracranial volumetric analysis technique to elucidate pathophysiological origins of SH in Alzheimer's disease (AD), vascular cognitive impairment (VCI) and normal aging (De Leeuw et al., 2001; Mayer and Kier, 1991; Pantoni and Garcia, 1997; Sachdev et al., 2008). The challenge is to develop processing tools that effectively and reliably quantify subcortical small vessel disease in the context of brain tissue compartments. Segmentation and brain region parcellation should account for SH subtypes which are often classified as: periventricular (pvSH) and deep white (dwSH), incidental white matter disease or lacunar infarcts and Virchow-Robin spaces. Lesion Explorer (LE) was developed as the final component of a comprehensive volumetric segmentation and parcellation image processing stream built upon previously published methods (Dade et al., 2004; Kovacevic et al., 2002). Inter-rater and inter-method reliability was accomplished both globally and regionally. Volumetric analysis showed high inter-rater reliability both globally (ICC=.99) and regionally (ICC=.98). Pixel-wise spatial congruence was also high (SI=.97). Whole brain pvSH volumes yielded high inter-rater reliability (ICC=.99). Volumetric analysis against an alternative kNN segmentation revealed high inter-method reliability (ICC=.97). Comparison with visual rating scales showed high significant correlations (ARWMC: r=.86; CHIPS: r=.87). The pipeline yields a comprehensive and reliable individualized volumetric profile for subcortical vasculopathy that includes regionalized (26 brain regions) measures for: GM, WM, sCSF, vCSF, lacunar and non-lacunar pvSH and dwSH.

Profiles by sex of brain MRI and cognitive function in the framingham offspring study

OBJECTIVE

To examine whether there are sex-specific associations between brain magnetic resonance imaging (MRI) measures and neuropsychologic (NP) test performance.

BACKGROUND

Differences in cardiovascular risk factors have been linked to decreased total cerebral brain volume and white matter hyperintensities (WMHs). Although brain morphology has been related to cognitive performance, few studies have addressed sex-specific effects in this relationship.

METHODS

Framingham Offspring who were stroke and dementia-free underwent a brain MRI scan and NP testing (n=2085; 978 men). Factor analysis identified 4 domain-specific NP factors. MRI participants were divided into 4 MRI subgroups based on measures of total cerebral brain volume and combinations of the presence of WMH and silent cerebral infarcts (> or =3 mm).

RESULTS

Overall, the relationship between MRI and NP measures was similar between the sexes. The exception was that only men showed a positive relationship between executive function and cerebrovascular disease defined as large WMH volume plus silent cerebral infarct. This finding was attributed only among men with Framingham Stroke Risk Profile scores >90th percentile range (P=0.0019).

CONCLUSIONS

Measures of brain atrophy and subclinical markers of vascular disease showed that sex does not significantly alter the relationship between MRI and NP, except among men and women who are at high risk for stroke; these men show poorer performance on executive function, whereas the women do not.

Cardiac index is associated with brain aging: the Framingham Heart Study

BACKGROUND

Cardiac dysfunction is associated with neuroanatomic and neuropsychological changes in aging adults with prevalent cardiovascular disease, theoretically because systemic hypoperfusion disrupts cerebral perfusion, contributing to subclinical brain injury. We hypothesized that cardiac function, as measured by cardiac index, would be associated with preclinical brain magnetic resonance imaging (MRI) and neuropsychological markers of ischemia and Alzheimer disease in the community.

METHODS AND RESULTS

Brain MRI, cardiac MRI, neuropsychological, and laboratory data were collected on 1504 Framingham Offspring Cohort participants free of clinical stroke, transient ischemic attack, or dementia (age, 61+/-9 years; 54% women). Neuropsychological and brain MRI variables were related to cardiac MRI-assessed cardiac index (cardiac output/body surface area). In multivariable-adjusted models, cardiac index was positively related to total brain volume (P=0.03) and information processing speed (P=0.02) and inversely related to lateral ventricular volume (P=0.048). When participants with clinically prevalent cardiovascular disease were excluded, the relation between cardiac index and total brain volume remained (P=0.02). Post hoc comparisons revealed that participants in the bottom cardiac index tertile (values <2.54) and middle cardiac index tertile (values between 2.54 and 2.92) had significantly lower brain volumes (P=0.04) than participants in the top cardiac index tertile (values >2.92).

CONCLUSIONS

Although observational data cannot establish causality, our findings are consistent with the hypothesis that decreasing cardiac function, even at normal cardiac index levels, is associated with accelerated brain aging.

Visceral fat is associated with lower brain volume in healthy middle-aged adults

OBJECTIVE

Midlife obesity has been associated with an increased risk of dementia. The underlying mechanisms are poorly understood. Our aim was to examine the cross-sectional association of body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and computed tomography (CT)-based measurements of subcutaneous (SAT) and visceral (VAT) adipose tissue with various magnetic resonance imaging (MRI) markers of brain aging in middle-aged community adults.

METHODS

Participants from the Framingham Offspring cohort were eligible if in addition to having measurements of BMI, WC, WHR, SAT, and VAT, they had undergone a volumetric brain MRI scan with measurements of total brain volume (TCBV), temporal horn volume (THV), white matter hyperintensity volume (WMHV), and MRI-defined brain infarcts (BI). All analyses were adjusted for age, sex, and time interval between abdominal CT and brain MRI.

RESULTS

In a sample of 733 community participants (mean age, 60 years; 53% women), we observed an inverse association of BMI (estimate by standard deviation unit +/- standard error = -0.27 +/- 0.12; p = 0.02), WC (-0.30 +/- 0.12; p = 0.01), WHR (-0.37 +/- 0.12; p = 0.02), SAT (-0.23 +/- 0.11; p = 0.04), and VAT (-0.36 +/- 0.12; p = 0.002) with TCBV, independent of vascular risk factors. The association between VAT and TCBV was the strongest and most robust, and was also independent of BMI (-0.35 +/- 0.15; p = 0.02) and insulin resistance (-0.32 +/- 0.13; p = 0.01). When adjusting for C-reactive protein levels, the associations were attenuated (-0.17 +/- 0.13; p = 0.17 for VAT). No consistently significant association was observed between the anthropometric or CT-based abdominal fat measurements and THV, WMHV, or BI.

INTERPRETATION

In middle-aged community participants, we observed a significant inverse association of anthropometric and CT-based measurements of abdominal, especially visceral, fat with total brain volume.

White matter hyperintensity and cognitive functioning in the racial and ethnic minority cohort of the Framingham Heart Study

BACKGROUND

Previous studies have demonstrated an association between white matter hyperintensities (WMH) and cognitive performance primarily in Caucasian samples, limiting generalizability to other ethnic and racial groups. This study investigated the association of WMH and cognition in an ethnic and racial minority cohort (Omni) of the Framingham Heart Study and compared these results to the Caucasian (Offspring) cohort.

METHODS

Quantitative brain MRI and neuropsychological evaluations were performed on stroke- and dementia-free participants. Cognitive assessment included verbal memory, visuospatial memory and organization, language, and executive functioning. Linear regression models were conducted to assess the association between WMH and cognitive function.

RESULTS

The Omni group presented with demographic factors that significantly differed from those of the Offspring group: they were younger, but had more stroke risk factors such as hypertension. In the Offspring group, WMH volume was significantly associated with poorer performance on tests of executive function and visual organization. No significant associations between WMH and cognitive measures were found in the Omni group, but no differences (significant interaction terms) were seen between the regression coefficients.

CONCLUSIONS

The Omni cohort had greater variability in factors that may mediate the association of WMH and cognition. More research is needed to investigate how stroke risk factors impact on the occurrence of WMH and its association with cognition in more diverse cohorts.

The association of magnetic resonance imaging measures with cognitive function in a biracial population sample

BACKGROUND

White matter hyperintensity volume (WMHV), cerebral infarcts, and total brain volume (TBV) are associated with cognitive function, but few studies have examined these associations in the general population or whether they differ by race.

OBJECTIVE

To examine the association of WMHV, cerebral infarcts, and TBV with global cognition and cognition in 5 separate domains in a biracial population sample.

SETTING

A biracial community population of Chicago, Illinois.

DESIGN

Cross-sectional population study.

PARTICIPANTS

The study population comprised 575 participants from the Chicago Health and Aging Project (CHAP).

MAIN OUTCOME MEASURES

Volumetric magnetic resonance imaging (MRI) measures of WMHV, TBV, and cerebral infarcts and detailed neuropsychological testing assessments of global cognition and 5 cognitive domains.

RESULTS

Overall and among those without dementia, cognition was inversely associated with WMHV and number of infarcts but was positively associated with TBV. When all 3 measures were simultaneously added to the model, the association of global cognition with WMHV and TBV remained significant and unchanged but was no longer significant with infarcts. Among subjects without dementia, all 3 MRI measures were associated with performance in multiple cognitive domains, specifically perceptual speed. However, among subjects with dementia, only TBV was associated with cognition and performance in multiple cognitive systems. Race did not significantly modify any of these associations.

CONCLUSIONS

In this biracial general population sample, the associations of MRI measures with cognition differed according to clinical status of subjects (stronger among subjects without dementia) and were not modified by race. These associations did not affect all cognitive domains equally but were more consistent with impairments in perceptual speed.

Long-term blood pressure fluctuation and cerebrovascular disease in an elderly cohort

BACKGROUND

The importance of subclinical cerebrovascular disease in the elderly is increasingly recognized, but its determinants have not been fully explicated. Elevated blood pressure (BP) and fluctuation in BP may lead to cerebrovascular disease through ischemic changes and compromised cerebral autoregulation.

OBJECTIVE

To determine the association of BP and long-term fluctuation in BP with cerebrovascular disease.

DESIGN

A community-based epidemiological study of older adults from northern Manhattan.

SETTING

The Washington Heights-Inwood Columbia Aging Project.

PARTICIPANTS

A total of 686 nondemented older adults who had BP measurements during 3 study visits at 24-month intervals and underwent structural magnetic resonance imaging (corresponding temporally with the third assessment). We derived the mean (SD) of the mean BP for each participant during the 3 intervals and divided the participants into 4 groups defined as below or above the group median (<or=96.48 or >96.48 mm Hg) and further subdivided them as below or above the median SD (<or=7.21 or >7.21 mm Hg). This scheme yielded 4 groups representing the full range of BPs and fluctuations in BP.

MAIN OUTCOME MEASURES

Differences in white matter hyperintensity (WMH) volume and presence of brain infarctions across groups.

RESULTS

White matter hyperintensity volume increased across the 4 groups in a linear manner, with the lowest WMH volume in the lowest mean/lowest SD group and the highest WMH volume in the highest mean/highest SD group (F(3,610) = 3.52, P = .02). Frequency of infarction also increased monotonically across groups (from 22% to 41%, P for trend = .004).

CONCLUSIONS

Compared with individuals with low BP and low fluctuations in BP, the risk of cerebrovascular disease increased with higher BP and BP fluctuations. Given that cerebrovascular disease is associated with disability, these findings suggest that interventions should focus on long-term fluctuating BP and elevated BP.

Measuring cognitive reserve based on the decomposition of episodic memory variance

In later adulthood brain pathology becomes common and trajectories of cognitive change are heterogeneous. Among the multiple determinants of late-life cognitive course, cognitive reserve has been proposed as an important factor that modifies or buffers the impact of brain pathology on cognitive function. This article presents and investigates a novel method for measuring and investigating such factors. The core concept is that in a population where pathology is common and variably present, 'reserve' may be defined as the difference between the cognitive performance predicted by an individual's level of pathology and that individual's actual performance. By this definition, people whose measured cognitive performance is better than predicted by pathology have high reserve, whereas those who perform worse than predicted have low reserve. To test this hypothesis, we applied a latent variable model to data from a diverse ageing cohort and decomposed the variance in a measure of episodic memory into three components, one predicted by demographics, one predicted by pathology as measured by structural MRI and a 'residual' or 'reserve' term that included all remaining variance. To investigate the plausibility of this approach, we then tested the residual component as an operational measure of reserve. Specific predictions about the effects of this putative reserve measure were generated from a general conceptual model of reserve. Each was borne from the results. The results show that the current level of reserve, as measured by this decomposition approach, modifies rates of conversion from mild cognitive impairment to dementia, modifies rates of longitudinal decline in executive function and, most importantly, attenuates the effect of brain atrophy on cognitive decline such that atrophy is more strongly associated with cognitive decline in subjects with low reserve than in those with high reserve. Decomposing the variance in cognitive function scores offers a promising new approach to the measure and study of cognitive reserve.

Whole brain quantitative T2 MRI across multiple scanners with dual echo FSE: applications to AD, MCI, and normal aging

The ability to pool data from multiple MRI scanners is becoming increasingly important with the influx in multi-site research studies. Fast spin echo (FSE) dual spin echo sequences are often chosen for such studies based principally on their short acquisition time and the clinically useful contrasts they provide for assessing gross pathology. The practicality of measuring FSE-T2 relaxation properties has rarely been assessed. Here, FSE-T2 relaxation properties are examined across the three main scanner vendors (General Electric (GE), Philips, and Siemens). The American College of Radiology (ACR) phantom was scanned on four 1.5T platforms (two GE, one Philips, and one Siemens) to determine if the dual echo pulse sequence is susceptible to vendor-based variance. In addition, data from 85 subjects spanning the spectrum of normal aging, mild cognitive impairment (MCI), and Alzheimer's disease (AD) was obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) to affirm the presence of any phantom based between vendor variance and determine the relationship between this variance and disease. FSE-T2 relaxation properties, including peak FSE-T2 and histogram width, were calculated for each phantom and human subject. Direct correspondence was found between the phantom and human subject data. Peak FSE-T2 of Siemens scanners was consistently at least 20ms prolonged compared to GE and Philips. Siemens scanners showed broader FSE-T2 histograms than the other scanners. Greater variance was observed across GE scanners than either Philips or Siemens. FSE-T2 differences were much greater with scanner vendor than between diagnostic groups, as no significant changes in peak FSE-T2 or histogram width between normal aged, MCI, and AD subject groups were observed. These results indicate that whole brain histogram measures are not sensitive enough to detect FSE-T2 changes between normal aging, MCI, and AD and that FSE-T2 is highly variable across scanner vendors.

The Relationship between age, injury severity, and MRI findings after traumatic brain injury

Age and injury severity are among the most significant predictors of outcome after traumatic brain injury (TBI). However, only a few studies have investigated the association between, age, injury severity, and the extent of brain damage in TBI. The purpose of this study was to investigate the association between age, measures of injury severity, and brain lesion volumes, as well as viable brain volumes, following TBI. Ninety-eight individuals with mild to very severe TBI (75.5% male, mean age at injury 34.5 years) underwent a structural MRI scan, performed with a 1.5-Tesla machine, on average 2.3 years post-injury. Lesion volumes were highly skewed in their distribution and were dichotomized for statistical purposes. Measures of injury severity were Glasgow Coma Scale score (GCS) and duration of post-traumatic amnesia (PTA). Logistic regression analyses predicting lesion volumes, controlling for participants' gender, cause of injury, time from injury to MRI scan, and total brain volume, revealed that both older age and longer PTA were associated with larger lesion volumes in both grey and white matter in almost all brain regions. Older age was also associated with smaller viable grey matter volumes in most neo-cortical brain regions, while longer PTA was associated with smaller viable white matter volumes in most brain regions. The results suggest that older age worsens the impact of TBI on the brain. They also indicate the validity of duration of PTA as a measure of injury severity that is not just related to one particular injury location.

Support for the vascular depression hypothesis in late-life depression: results of a 2-site, prospective, antidepressant treatment trial

CONTEXT

Research on vascular depression has used 2 approaches to subtype late-life depression, based on executive dysfunction or white matter hyperintensity severity.

OBJECTIVE

To evaluate the relationship of neuropsychological performance and white matter hyperintensity with clinical response in late-life depression.

DESIGN

Two-site, prospective, nonrandomized controlled trial.

SETTING

Outpatient clinics at Washington University and Duke University.

PARTICIPANTS

A total of 217 subjects aged 60 years or older met DSM-IV criteria for major depression, scored 20 or more on the Montgomery-Asberg Depression Rating Scale (MADRS), and received vascular risk factor scores, neuropsychological testing, and magnetic resonance imaging; they were excluded for cognitive impairment or severe medical disorders. Fazekas rating was conducted to grade white matter hyperintensity lesions. Intervention Twelve weeks of sertraline treatment, titrated by clinical response. Main Outcome Measure Participants' MADRS scores over time.

RESULTS

Baseline neuropsychological factor scores correlated negatively with baseline Fazekas scores. A mixed model examined effects of predictor variables on MADRS scores over time. Baseline episodic memory (P = .002), language (P = .007), working memory (P = .01), processing speed (P < .001), executive function factor scores (P = .002), and categorical Fazekas ratings (P = .05) predicted MADRS scores, controlling for age, education, age of onset, and race. Controlling for baseline MADRS scores, these factors remained significant predictors of decrease in MADRS scores, except for working memory and Fazekas ratings. Thirty-three percent of subjects achieved remission (MADRS < or =7). Remitters differed from nonremitters in baseline cognitive processing speed, executive function, language, episodic memory, and vascular risk factor scores.

CONCLUSIONS

Comprehensive neuropsychological function and white matter hyperintensity severity predicted MADRS scores prospectively over a 12-week treatment course with selective serotonin reuptake inhibitors in late-life depression. Baseline neuropsychological function differentiated remitters from nonremitters and predicted time to remission in a proportional hazards model. Predictor variables correlated highly with vascular risk factor severity. These data support the vascular depression hypothesis and highlight the importance of linking subtypes based on neuropsychological function and white matter integrity.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00045773.

Social and emotional aging

The past several decades have witnessed unidimensional decline models of aging give way to life-span developmental models that consider how specific processes and strategies facilitate adaptive aging. In part, this shift was provoked by the stark contrast between findings that clearly demonstrate decreased biological, physiological, and cognitive capacity and those suggesting that people are generally satisfied in old age and experience relatively high levels of emotional well-being. In recent years, this supposed "paradox" of aging has been reconciled through careful theoretical analysis and empirical investigation. Viewing aging as adaptation sheds light on resilience, well-being, and emotional distress across adulthood.

Aging effects on recollection and familiarity: the role of white matter hyperintensities

Previous studies have indicated that aging is associated with declines in recollection whereas familiarity-based recognition is left largely unaffected. The brain changes underlying these recollection declines are yet not well understood. In the current study we examined the role of white matter integrity as measured by white matter hyperintensities (WMH) on age-related changes in recollection and familiarity. Recognition was measured using a remember/know procedure (Experiment 1) and a source-memory process-dissociation procedure (Experiment 2). Robust age related declines in recollection were observed, but there was no evidence that white matter damage was related to the observed memory declines. Although future studies with larger samples will be necessary to fully characterize the role of WMH in normal age-related declines in different types of memory, the results suggest that declines in recollection are not strongly related to the brain changes indexed by WMHs.

Association of MRI markers of vascular brain injury with incident stroke, mild cognitive impairment, dementia, and mortality: the Framingham Offspring Study

BACKGROUND AND PURPOSE

White matter hyperintensities and MRI-defined brain infarcts (BIs) have individually been related to stroke, dementia, and mortality in population-based studies, mainly in older people. Their significance in middle-aged community-dwelling persons and the relative importance of these associations remain unclear. We simultaneously assessed the relation of white matter hyperintensities and BI with incident stroke, mild cognitive impairment, dementia, and mortality in a middle-aged community-based cohort.

METHODS

A total of 2229 Framingham Offspring Study participants aged 62+/-9 years underwent volumetric brain MRI and neuropsychological testing (1999 to 2005). Incident stroke, dementia, and mortality were prospectively ascertained and for 1694 participants in whom a second neuropsychological assessment was performed (2005 to 2007), incident mild cognitive impairment was evaluated. All outcomes were related to white matter hyperintensities volume (WMHV), age-specific extensive WMHV and BI adjusting for age and gender.

RESULTS

Extensive WMHV and BI were associated with an increased risk of stroke (hazard ratio [HR]=2.28, 95% CI: 1.02 to 5.13; HR=2.84, 95% CI: 1.32 to 6.10). WMHV, extensive WMHV, and BI were associated with an increased risk of dementia (HR=2.22, 95% CI: 1.32 to 3.72; HR=3.97, 95% CI: 1.10 to 14.30; HR=6.12, 95% CI: 1.82 to 20.54) independently of vascular risk factors and interim stroke. WMHV and extensive WMHV were associated with incident amnestic mild cognitive impairment in participants aged > or = 60 years only (OR=2.47, 95% CI: 1.31 to 4.66 and OR=1.49, 95% CI: 1.14 to 1.97). WMHV and extensive WMHV were associated with an increased risk of death (HR=1.38, 95% CI: 1.13 to 1.69; HR=2.27, 95% CI: 1.41 to 3.65) independent of vascular risk factors and of interim stroke and dementia.

CONCLUSIONS

In a large community-based sample of middle-aged adults, BI predicted an increased risk of stroke and dementia independent of vascular risk factors. White matter hyperintensities portended an increased risk of stroke, amnestic mild cognitive impairment, dementia, and death independent of vascular risk factors and interim vascular events.

Brain aging and gait

Aging is associated with a reduction in several functions including gait. The preservation of gait is important in order to prevent falls and consequent injury as one gets older. Poorer gait may also be an important marker for health status and a determinant of quality of life in later life. It is now recognized that specific regions of the brain such as the frontal motor, prefrontal and parietal cortices, the basal ganglia and cerebellum play an important role in the initiation, planning, execution and maintenance of gait, in tandem with other neuromuscular factors. Aging and age-related disease may affect areas of the brain that are involved in the regulation of gait. Recent technological advances in brain imaging have enabled the identification of age-related changes occurring in the brain, such as cortical atrophy, brain infarctions or cerebral white matter lesions. There is a small, but growing, amount of research examining the association between these changes and gait. The objective of this review is to summarize the current state of knowledge on the impact of the aging brain on gait, and to identify directions for future research. Such research may lead to the development of interventions aimed at preventing or reducing the effect of brain aging on gait.

Bivariate heritability of total and regional brain volumes: the Framingham Study

Heritability and genetic and environmental correlations of total and regional brain volumes were estimated from a large, generally healthy, community-based sample, to determine if there are common elements to the genetic influence of brain volumes and white matter hyperintensity (WMH) volume. There were 1538 Framingham Heart Study participants with brain volume measures from quantitative magnetic resonance imaging who were free of stroke and other neurologic disorders that might influence brain volumes and who were members of families with at least 2 Framingham Heart Study participants. Heritability was estimated using variance component methodology and adjusting for the components of the Framingham stroke risk profile. Genetic and environmental correlations between traits were obtained from bivariate analysis. Heritability estimates ranging from 0.46 to 0.60 were observed for total brain, WMH, hippocampal, temporal lobe, and lateral ventricular volumes. Moderate, yet significant, heritability was observed for the other measures. Bivariate analyses demonstrated that relationships between brain volume measures, except for WMH, reflected both moderate to strong shared genetic and shared environmental influences. This study confirms strong genetic effects on brain and WMH volumes. These data extend current knowledge by showing that these 2 different types of magnetic resonance imaging measures do not share underlying genetic or environmental influences.

Genome-wide association studies of MRI-defined brain infarcts: meta-analysis from the CHARGE Consortium

BACKGROUND AND PURPOSE

Previous studies examining genetic associations with MRI-defined brain infarct have yielded inconsistent findings. We investigated genetic variation underlying covert MRI infarct in persons without histories of transient ischemic attack or stroke. We performed meta-analysis of genome-wide association studies of white participants in 6 studies comprising the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium.

METHODS

Using 2.2 million genotyped and imputed single nucleotide polymorphisms, each study performed cross-sectional genome-wide association analysis of MRI infarct using age- and sex-adjusted logistic regression models. Study-specific findings were combined in an inverse-variance-weighted meta-analysis, including 9401 participants with mean age 69.7 (19.4% of whom had >or=1 MRI infarct).

RESULTS

The most significant association was found with rs2208454 (minor allele frequency, 20%), located in intron 3 of MACRO domain containing 2 gene and in the downstream region of fibronectin leucine-rich transmembrane protein 3 gene. Each copy of the minor allele was associated with lower risk of MRI infarcts (odds ratio, 0.76; 95% confidence interval, 0.68-0.84; P=4.64x10(-7)). Highly suggestive associations (P<1.0x10(-5)) were also found for 22 other single nucleotide polymorphisms in linkage disequilibrium (r(2)>0.64) with rs2208454. The association with rs2208454 did not replicate in independent samples of 1822 white and 644 black participants, although 4 single nucleotide polymorphisms within 200 kb from rs2208454 were associated with MRI infarcts in the black population sample.

CONCLUSIONS

This first community-based, genome-wide association study on covert MRI infarcts uncovered novel associations. Although replication of the association with top single nucleotide polymorphisms failed, possibly because of insufficient power, results in the black population sample are encouraging, and further efforts at replication are needed.

Differences in brain volume, hippocampal volume, cerebrovascular risk factors, and apolipoprotein E4 among mild cognitive impairment subtypes

OBJECTIVES

To evaluate demographics, magnetic resonance imaging (MRI) measures, and vascular risk among mild cognitive impairment (MCI) subtypes.

DESIGN

Cross-sectional study.

SETTING

Both clinics and the community.

PARTICIPANTS

A total of 153 subjects with MCI, 218 cognitively normal older individuals (controls), and 68 patients with Alzheimer disease.

MAIN OUTCOME MEASURES

Classification of subjects with MCI according to current subtype diagnostic convention based on neuropsychological performance, estimates of vascular risk based on medical history, research MRI unless there was a specific contraindication, and apolipoprotein E genotype.

RESULTS

Of the 153 subjects with MCI, 65 were diagnosed with amnestic single-domain, 46 with amnestic multiple-domain, 27 with nonamnestic single-domain, and 15 with nonamnestic multiple-domain MCI. Analyses of control, MCI, and Alzheimer disease cases revealed significant differences in brain and hippocampal volumes between each group. Post hoc analyses of MRI measures among the MCI subtypes found that patients with amnestic single-domain MCI had significantly less brain atrophy and that hippocampal volume differed significantly from controls for the 2 amnestic forms of MCI. Apolipoprotein E genotype prevalence was significantly greater in the amnestic and nonamnestic subtypes of MCI. Conversely, the nonamnestic subtypes were more likely to have increased vascular risk and to be African American.

CONCLUSIONS

Amnestic forms of MCI appear to have demographic, genetic, and MRI findings suggestive of Alzheimer disease pathology, whereas the nonamnestic forms of MCI have findings suggestive of vascular disease. Importantly, however, all subjects with MCI showed evidence of brain injury, and the biological differences among subtypes are relatively subtle beyond the memory vs nonmemory groupings.

Association of plasma leptin levels with incident Alzheimer disease and MRI measures of brain aging

CONTEXT

The adipokine leptin facilitates long-term potentiation and synaptic plasticity in the hippocampus, promotes beta-amyloid clearance, and improves memory function in animal models of aging and Alzheimer disease (AD).

OBJECTIVE

To relate baseline circulating leptin concentrations in a community-based sample of individuals without dementia to incident dementia and AD during follow-up and magnetic resonance imaging (MRI) measures of brain aging in survivors.

DESIGN, SETTING, AND PARTICIPANTS

Prospective study of plasma leptin concentrations measured in 785 persons without dementia (mean [SD] age, 79 [5] years; 62% female), who were in the Framingham original cohort at the 22nd examination cycle (1990-1994). A subsample of 198 dementia-free survivors underwent volumetric brain MRI between 1999 and 2005, approximately 7.7 years after leptin was assayed. Two measures of brain aging, total cerebral brain volume and temporal horn volume (which is inversely related to hippocampal volume) were assessed.

MAIN OUTCOME MEASURE

Incidence of dementia and AD during follow-up until December 31, 2007.

RESULTS

During a median follow-up of 8.3 years (range, 0-15.5 years), 111 participants developed incident dementia; 89 had AD. Higher leptin levels were associated with a lower risk of incident dementia and AD in multivariable models (hazard ratio per 1-SD increment in log leptin was 0.68 [95% confidence interval, 0.54-0.87] for all-cause dementia and 0.60 [95% confidence interval, 0.46-0.79] for AD). This corresponds to an absolute AD risk over a 12-year follow-up of 25% for persons in the lowest quartile (first quartile) vs 6% for persons in the fourth quartile of sex-specific leptin levels. In addition, a 1-SD elevation in plasma leptin level was associated with higher total cerebral brain volume and lower temporal horn volume, although the association of leptin level with temporal horn volume did not reach statistical significance.

CONCLUSION

Circulating leptin was associated with a reduced incidence of dementia and AD and with cerebral brain volume in asymptomatic older adults.

Association of parental dementia with cognitive and brain MRI measures in middle-aged adults

OBJECTIVES

Studies of autosomal dominant Alzheimer disease (AD) have shown structural and cognitive changes in mutation carriers decades prior to clinical disease. Whether such changes are detectable in offspring of persons with sporadic dementia remains unknown. We related prospectively verified parental dementia to brain MRI and cognitive testing in the offspring, within a 2-generational community-based cohort.

METHODS

A total of 717 Framingham offspring (mean age: 59 +/- 8 years) were studied. In multivariate analyses, we compared offspring with and without verified parental dementia (and AD) for 1) performance on tests of memory, abstract reasoning, and cognitive flexibility, and 2) volumetric brain MRI measures of total cerebral brain volume (TCBV), hippocampal volume (HV), and white matter hyperintensity volume (WMHV), assessed cross-sectionally and longitudinally.

RESULTS

When testing the association of parental dementia and AD with baseline cognitive performance, we observed an interaction of parental dementia and AD with APOE epsilon4 status (p < 0.002). In APOE epsilon4 carriers only (n = 165), parental dementia was associated with poorer scores on tests of verbal memory (beta = -1.81 +/- 0.53, p < 0.001) and visuospatial memory (beta = -1.73 +/- 0.47, p < 0.001). These associations were stronger for parental AD (beta = -1.97 +/- 0.52, p < 0.001, beta = -1.95 +/- 0.48, p < 0.001), equivalent to 14-16 years of brain aging. Among APOE epsilon4 carriers, offspring of participants with dementia were also more likely to show an annual decline in TCBV in the top quartile (odds ratio = 4.67 [1.26-17.30], p = 0.02). Regardless of APOE epsilon4 status, participants with parental dementia were more likely to be in the highest quartile of decline in executive function test scores (odds ratio = 1.61 [1.02-2.53], p = 0.04).

CONCLUSIONS

Among middle-aged carriers of the APOE epsilon4 allele, parental dementia and Alzheimer disease were associated with poorer verbal and visuospatial memory and a higher rate of global brain atrophy.

Endophenotypes in normal brain morphology and Alzheimer's disease: a review

Late-onset Alzheimer's disease is a common complex disorder of old age. Though these types of disorders can be highly heritable, they differ from single-gene (Mendelian) diseases in that their causes are often multifactorial with both genetic and environmental components. Genetic risk factors that have been firmly implicated in the cause are mutations in the amyloid precursor protein (APP), presenilin 1 (PSEN1) and presenilin 2 (PSEN2) genes, which are found in large multi-generational families with an autosomal dominant pattern of disease inheritance, the apolipoprotein E (APOE)epsilon4 allele and the sortilin-related receptor (SORL1) gene. Environmental factors that have been associated with late-onset Alzheimer's disease include depressive illness, various vascular risk factors, level of education, head trauma and estrogen replacement therapy. This complexity may help explain their high prevalence from an evolutionary perspective, but the etiologic complexity makes identification of disease-related genes much more difficult. The "endophenotype" approach is an alternative method for measuring phenotypic variation that may facilitate the identification of susceptibility genes for complexly inherited traits. The usefulness of endophenotypes in genetic analyses of normal brain morphology and, in particular for Alzheimer's disease will be reviewed as will the implications of these findings for models of disease causation. Given that the pathways from genotypes to end-stage phenotypes are circuitous at best, identifying endophenotypes more proximal to the effects of genetic variation may expedite the attempts to link genetic variants to disorders.

A uniform approach to modeling risk factor relationships for ischemic lesion prevalence and extent: the Women's Health Initiative Magnetic Resonance Imaging study

BACKGROUND

Both the prevalence and extent of brain magnetic resonance imaging (MRI) abnormalities are related to risk factors for dementia. Typically these associations have been explored separately, but an integrated modeling approach would allow the separate relationships to be consistently described and contrasted.

METHODS

Region-specific measures of ischemic lesion volumes were obtained from standardized brain MRI from 1,403 women enrolled in the Women's Health Initiative hormone therapy trials. Mixed-effects mixed-distribution models were fitted to explore jointly the relationships that the region-specific prevalence of ischemic lesions and region-specific ischemic lesion volumes had with risk factors and scores from tests of cognitive function.

RESULTS

Women with greater probabilities (prevalence) of having ischemic lesions in brain regions also tended to have larger volumes (extent) of ischemic lesions within the affected regions (p < 0.001). Across the 5 regions included in analyses (frontal, limbic, occipital, parietal and temporal), prevalence and extent varied (p < 0.001). Each was increased among women who were older, had hypertension or who had previously been classified as cognitively impaired (p < 0.01). Additionally, extent was significantly increased among women with a history of smoking (p = 0.02). Cognitive function tests were more strongly related to the extent than prevalence of ischemic lesions and relationships varied among cognitive domains (p < 0.001).

CONCLUSIONS

Mixed-effects mixed-distribution models provide a coherent basis for examining relationships involving the prevalence and extent of ischemic brain lesions. Across the cohort and regions we examined, relationships with risk factors and cognitive function appeared to be stronger for extent than for prevalence.

Age, Alzheimer disease, and brain structure

BACKGROUND

Lack of clear understanding remains on the overlapping atrophy patterns of aging and early Alzheimer disease (AD) pathology in gray matter (GM) of the brain in vivo.

OBJECTIVE

To evaluate the independent and overlapping patterns of GM atrophy in normal aging and AD.

METHODS

A total of 169 cognitively normal subjects and 33 persons with probable AD enrolled in the longitudinal Cardiovascular Health Study-Cognition Study underwent 3-dimensional volumetric MRI scans. Controls remained cognitively normal for at least 5 years after their MRI scans and the probable AD subjects were relatively early in their clinical course with an average modified Mini-Mental State Examination score of 76/100. The scans were analyzed using voxel-based morphometry adjusting for total intracranial volume, gender, education, and race.

RESULTS

With older age, GM volume was lower in the sensorimotor and heteromodal association areas in frontal, temporal, occipital, and parietal lobes, as well as in the cerebellum (false discovery rate p = 0.05). Additional atrophy was observed in the posterior hippocampus, thalamus, and middle cingulate gyrus. By contrast, atrophy was seen in subjects with AD in the anterior hippocampal/parahippocampal regions and the precuneus. Normal aging and AD overlapped in the hippocampal body and the entorhinal cortex.

CONCLUSION

Brain atrophy with aging was observed in supratentorial and infratentorial areas, as well in primary motor, sensory, and heteromodal association regions. Age and Alzheimer disease exert independent gray matter atrophy patterns but these effects overlapped substantially in the hippocampus and entorhinal cortex.

Regional pattern of white matter microstructural changes in normal aging, MCI, and AD

OBJECTIVE

To cross-sectionally compare the regional white matter fractional anisotropy (FA) of cognitively normal (CN) older individuals and patients with mild cognitive impairment (MCI) and Alzheimer disease (AD), separately focusing on the normal-appearing white matter (NAWM) and white matter hyperintensities (WMH), and to test the independent effects of presumed degenerative and vascular process on FA differences.

METHODS

Forty-seven patients with AD, 73 patients with MCI, and 95 CN subjects received diffusion tensor imaging and vascular risk evaluation. To properly control normal regional variability of FA, we divided cerebral white matter into 4 strata as measured from a series of young healthy individuals (H1 = highest; H2 = intermediate high; H3 = intermediate low; H4 = lowest anisotropy stratum).

RESULTS

For overall cerebral white matter, patients with AD had significantly lower FA than CN individuals or patients with MCI in the regions with higher baseline anisotropy (H1, H2, and H3), corresponding to long corticocortical association fibers, but not in H4, which mostly includes heterogeneously oriented fibers. Vascular risk showed significant independent effects on FA in all strata except H1, which corresponds to the genu and splenium of the corpus callosum. Similar results were found within NAWM. FA in WMH was significantly lower than NAWM across all strata but was not associated with diagnosis or vascular risk.

CONCLUSIONS

Both vascular and Alzheimer disease degenerative process contribute to microstructural injury of cerebral white matter across the spectrum of cognitive ability and have different region-specific injury patterns.

Age-related differences in regional brain volumes: a comparison of optimized voxel-based morphometry to manual volumetry

Regional manual volumetry is the gold standard of in vivo neuroanatomy, but is labor-intensive, can be imperfectly reliable, and allows for measuring limited number of regions. Voxel-based morphometry (VBM) has perfect repeatability and assesses local structure across the whole brain. However, its anatomic validity is unclear, and with its increasing popularity, a systematic comparison of VBM to manual volumetry is necessary. The few existing comparison studies are limited by small samples, qualitative comparisons, and limited selection and modest reliability of manual measures. Our goal was to overcome those limitations by quantitatively comparing optimized VBM findings with highly reliable multiple regional measures in a large sample (N=200) across a wide agespan (18-81). We report a complex pattern of similarities and differences. Peak values of VBM volume estimates (modulated density) produced stronger age differences and a different spatial distribution from manual measures. However, when we aggregated VBM-derived information across voxels contained in specific anatomically defined regions (masks), the patterns of age differences became more similar, although important discrepancies emerged. Notably, VBM revealed stronger age differences in the regions bordering CSF and white matter areas prone to leukoaraiosis, and VBM was more likely to report nonlinearities in age-volume relationships. In the white matter regions, manual measures showed stronger negative associations with age than the corresponding VBM-based masks. We conclude that VBM provides realistic estimates of age differences in the regional gray matter only when applied to anatomically defined regions, but overestimates effects when individual peaks are interpreted. It may be beneficial to use VBM as a first-pass strategy, followed by manual measurement of anatomically defined regions.

Changes in intellectual functioning associated with normal aging

Declines in IQ scores with advancing age have been observed in each successive revision of the Wechsler Intelligence Scales. This study examined age-related changes on the fourth edition of the Wechsler Adult Intelligence Scale and compared these to the effects seen on the 1955, 1981, and 1997 standardizations of the scales. The most pronounced declines were in measures of processing speed and nonverbal reasoning. Declines in nonverbal reasoning were similar on timed and un-timed measures. Verbal abilities remained relatively stable across the life span. General intelligence as assessed by the Full Scale IQ was reduced about 1 SD by age 75 when corrections for age were removed. Age-related declines have become less pronounced since 1955, particularly on measures of processing speed. This effect was essentially linear, unrelated to concurrent IQ increases in the general population, and paralleled a 9-year increase in life expectancy during this time period.

Subclinical cerebrovascular disease in mild cognitive impairment

BACKGROUND

Cerebrovascular disease (CVD) may contribute to mild cognitive impairment (MCI). We sought to determine the relation of white matter hyperintensity (WMH) volume and infarcts in brain MRI to MCI in a community-based sample.

METHODS

A total of 679 elderly persons without dementia underwent brain MRI. WMH and infarcts were quantified using research methods. WMH was adjusted for total cranial volume. The Petersen criteria were used to define MCI. MCI was further subclassified into amnestic and non-amnestic. We used logistic regression to relate WMH and infarcts to prevalent MCI.

RESULTS

WMH were associated with amnestic MCI (odds ratio [OR] = 1.9; 95% confidence interval [CI] 1.1, 3.4) but not non-amnestic MCI (OR = 1.2; 95% CI 0.4, 1.6) after adjusting for age, gender, ethnic group, education, and APOE-epsilon4. Infarcts were more strongly associated with non-amnestic MCI (OR = 2.7; 95% CI 1.5, 4.8) than amnestic MCI (OR = 1.4; 95% CI 0.9, 2.3). In secondary analyses using continuous cognitive scores as outcomes, WMH, but not infarcts, were related to memory, while infarcts were more strongly related with non-amnestic domains.

CONCLUSION

White matter hyperintensity (WMH) is more strongly related to amnestic mild cognitive impairment (MCI). Infarcts are more strongly related to non-amnestic MCI. The nature of WMH in amnestic MCI requires further study.

Association of plasma ADMA levels with MRI markers of vascular brain injury: Framingham offspring study

BACKGROUND AND PURPOSE

Asymmetrical dimethylarginine (ADMA), an inhibitor of endothelial nitric oxide synthase, is a marker of endothelial dysfunction. Elevated circulating ADMA concentrations have been associated with systemic and carotid atherosclerosis, an elevated risk of developing stroke, and magnetic resonance imaging white-matter hyperintensities (WMHs). The relation of plasma ADMA to subclinical vascular brain injury has not been previously studied in a middle-aged, community-based sample.

METHODS

In 2013 stroke-free Framingham offspring (mean+/-SD age, 58+/-9.5 years; 53% women), we related baseline plasma ADMA levels (1995-1998) to subsequent brain magnetic resonance imaging measures (1999-2004) of subclinical vascular injury: presence of silent brain infarcts (SBIs) and large white-matter hyperintensity volumes (LWMHs; defined as >1 SD above the age-specific mean).

RESULTS

Prevalences of SBIs and LWMHs were 10.7% and 12.6%, respectively. In multivariable analyses adjusting for age, sex and traditional stroke risk factors, higher ADMA levels were associated with an increased risk of prevalent SBIs (odds ratio [OR] per 1-SD increase in ADMA=1.16; 95% CI, 1.01 to 1.33; P=0.04). We observed that participants in the upper 3 age-specific quartiles (Qs) of plasma ADMA values had an increased prevalence of SBIs (OR for Q2-Q4 vs Q1=1.43; 95% CI, 1.00 to 2.04; P<0.05). The prevalence of SBIs in Q1and Q2-Q4 was 8.3% and 11.6%, respectively. The prevalence of LWMHs did not differ according to ADMA concentrations.

CONCLUSIONS

Higher plasma ADMA values were associated with an increased prevalence of SBIs, after adjustment for traditional stroke risk factors. Thus, ADMA may be a potentially useful new biomarker of subclinical vascular brain injury, which is an important correlate of vascular cognitive impairment and risk of stroke.

Structural neuroimaging in Altheimer's disease: do white matter hyperintensities matter?

The targeted brain dysfunction that accompanies aging can have a devastating effect on cognitive and intellectual abilities. A significant proportion of older adults experience precipitous cognitive decline that negatively impacts functional activities. Such individuals meet clinical diagnostic criteria for dementia, which is commonly attributed to Alzheimer's disease (AD). Structural neuroimaging, including magnetic resonance imaging (MRI), has contributed significantly to our understanding of the morphological and pathology-related changes that may underlie normal and disease-associated cognitive change in aging. White matter hyperintensities (WMH), which are distributed patches of increased hyperintense signal on T2-weighted MRI, are among the most common structural neuroimaging findings in older adults. In recent years, WMH have emerged as robust radiological correlates of cognitive decline. Studies suggest that WMH distributed in anterior brain regions are related to decline in executive abilities that is typical of normal aging, whereas WMH distributed in more posterior brain regions are common in AD. Although epidemiological, observational, and pathological studies suggest that WMH may be ischemic in origin and caused by consistent or variable hypoperfusion, there is emerging evidence that they may also reflect vascular deposition of (β-amyloid, particularly when they are distributed in posterior areas and are present in patients with AD. Findings from the literature highlight the potential contribution of small-vessel cerebrovascular disease to the pathogenesis of AD, and suggest a mechanistic interaction, but future longitudinal studies using multiple imaging modalities are required to fully understand the complex role of WMH in AD.

The Italian Brain Normative Archive of structural MR scans: norms for medial temporal atrophy and white matter lesions

BACKGROUND AND AIMS

To describe the clinical and neuropsychological features of a large group of cognitively intact persons subjected to brain high-resolution magnetic resonance (MR), to compare them with the general population, and to set norms for medial temporal atrophy and white matter lesions.

METHODS

Participants in the Italian Brain Normative Archive (IBNA) study were 483 consecutive volunteers undergoing MR for reasons unrelated to cognition (migraine or headache, visual and balance or auditory disturbances, paresthesias, and others) and showing no brain damage. Manual tracing of hippocampal and amygdalar volumes and visual rating of white matter lesions were made. The whole study group was stratified by age (</=60 and 60+ yrs) and by the reason for MR prescription.

RESULTS

In the whole group, mean age and education were 52.4+/-13.7 and 9.8+/-4.2 years, respectively, and the prevalence of women was 63%. Clinical, neuropsychological and morphometric features were similar in the stratified subgroups. Neuropsychological features were those expected for age and education based on Italian normative values. Hippocampal and amygdalar volumes were not associated with age, except for the right amygdala (B -0.159, 95% CI -0.28 to -0.03, p=0.016).

CONCLUSIONS

Persons in the IBNA study had clinical and neuropsychological features consistent with that of the general population. Their brain morphometric features may be used as normative references for patients with suspected neurodegenerative disorders.

White matter pathways associated with working memory in normal aging

INTRODUCTION

Previous studies by our group have found that white matter integrity as determined by Diffusion Tensor Imaging (DTI) is associated with working memory decline. It has been proposed that subtle white matter integrity loss may lead to the disruption of working memory in particular because it relies on the dynamic and reiterative activity of cortico-cortical pathways.

METHODS

DTI and working memory measurement were acquired for 99 adults from our GENIE study of healthy middle aged and elderly individuals. Voxel-based statistics were used to identify clusters of voxels in mean diffusivity images specifically associated with variations in working memory performance. Tractography then identified the cortico-cortical white matter pathways passing through these clusters, between the temporal, parietal and frontal cortices.

RESULTS

Significant clusters were identified which were associated with working memory in the white matter of the temporal and frontal lobes, the cingulate gyrus, and in the thalamus. The tracts that passed through these clusters included the superior parietal lobule pathway, the medial temporo-frontal pathway, the uncinate fasciculus, the fronto-parietal fasciculus, and the cingulum.

CONCLUSIONS

Significant clusters were identified in the white matter that were associated with working memory performance. Tractography performed through these clusters identified white matter fiber tracts which pass between grey matter regions known to be activated by working memory tasks and also mirror working memory pathways suggested by previous functional connectivity imaging.

White matter lesion extension to automatic brain tissue segmentation on MRI

A fully automated brain tissue segmentation method is optimized and extended with white matter lesion segmentation. Cerebrospinal fluid (CSF), gray matter (GM) and white matter (WM) are segmented by an atlas-based k-nearest neighbor classifier on multi-modal magnetic resonance imaging data. This classifier is trained by registering brain atlases to the subject. The resulting GM segmentation is used to automatically find a white matter lesion (WML) threshold in a fluid-attenuated inversion recovery scan. False positive lesions are removed by ensuring that the lesions are within the white matter. The method was visually validated on a set of 209 subjects. No segmentation errors were found in 98% of the brain tissue segmentations and 97% of the WML segmentations. A quantitative evaluation using manual segmentations was performed on a subset of 6 subjects for CSF, GM and WM segmentation and an additional 14 for the WML segmentations. The results indicated that the automatic segmentation accuracy is close to the interobserver variability of manual segmentations.

Relaxo-volumetric multispectral quantitative magnetic resonance imaging of the brain over the human lifespan: global and regional aging patterns

The objective of this study was to determine the T1, T2 and secular-T2 relaxo-volumetric brain aging patterns using multispectral quantitative magnetic resonance imaging, both globally and regionally, and covering an age range approaching the full human lifespan. Fifty-one subjects (28 males, 23 females; age range: 0.5-87 years) were studied consisting of 18 healthy volunteers and 33 patients. Patients were selected after carefully reviewing their radiology reports to have either normal-by-MRI findings (25 patient subjects) or small focal pathology less than 6 mm in size (eight patient subjects). All subjects were MR imaged at 1.5 T with the mixed turbo spin echo pulse sequence. The soft tissues inside the cranial vault, termed intracranial matter (ICM), were segmented using a dual-clustering segmentation algorithm. ICM segments were further divided into six subsegments: bilateral anterior cerebral, posterior cerebral and cerebellar subsegments. T1, T2 and secular-T2 relaxation time histograms of all segments were generated and modeled with Gaussian functions. For each segment, the volumes of white matter, gray matter and cerebrospinal fluid were calculated from the T1 histograms. The age-related tendencies of three quantitative MRI parameters (T1, T2 and secular-T2) and the fractional tissue volumes showed four distinct periods of life, specifically a maturation period (0-2 years), a development period (2-20 years), an adulthood period (20-60 years) and a senescence period (60 years and older). For all ages, the anterior cerebral subsegment exhibited consistently longer gray matter T1s and shorter white matter T1s than the posterior cerebral and cerebellar subsegments. Volumetric age-related changes of the cerebellar subsegment were more gradual than in the cerebral subsegments. This study shows that relaxometric and volumetric age-related changes are synchronized and define the same four periods of brain evolution both globally and regionally.

Validity of self-reported stroke in elderly African Americans, Caribbean Hispanics, and Whites

BACKGROUND

The validity of a self-reported stroke remains inconclusive.

OBJECTIVE

To validate the diagnosis of self-reported stroke using stroke identified by magnetic resonance imaging (MRI) as the standard.

DESIGN, SETTING, AND PARTICIPANTS

Community-based cohort study of nondemented, ethnically diverse elderly persons in northern Manhattan.

METHODS

High-resolution quantitative MRIs were acquired for 717 participants without dementia. Sensitivity and specificity of stroke by self-report were examined using cross-sectional analyses and the chi(2) test. Putative relationships between factors potentially influencing the reporting of stroke, including memory performance, cognitive function, and vascular risk factors, were assessed using logistic regression models. Subsequently, all analyses were repeated, stratified by age, sex, ethnic group, and level of education.

RESULTS

In analyses of the whole sample, sensitivity of stroke self-report for a diagnosis of stroke on MRI was 32.4%, and specificity was 78.9%. In analyses stratified by median age (80.1 years), the validity between reported stroke and detection of stroke on MRI was significantly better in the younger than the older age group (for all vascular territories: sensitivity and specificity, 36.7% and 81.3% vs 27.6% and 26.2%; P = .02). Impaired memory, cognitive skills, or language ability and the presence of hypertension or myocardial infarction were associated with higher rates of false-negative results.

CONCLUSIONS

Using brain MRI as the standard, specificity and sensitivity of stroke self-report are low. Accuracy of self-report is influenced by age, presence of vascular disease, and cognitive function. In stroke research, sensitive neuroimaging techniques rather than stroke self-report should be used to determine stroke history.

Age and education effects on relationships of cognitive test scores with brain structure in demographically diverse older persons

This study examined how age and education influence the relationship between neuropsychological test scores and brain structure in demographically diverse older adults spanning the range from normal cognition to dementia. A sample of 351 African Americans, 410 Hispanics, and 458 Whites underwent neuropsychological testing. Volumetric magnetic resonance imaging (MRI) measures of total brain, white matter hyperintensity, and hippocampus were available for 79 African Americans, 102 Hispanics, and 134 Whites. The authors used latent variable modeling to examine effects of age, education, and brain volumes on test scores and determine how much variance brain volumes explained in unadjusted and age- and education-adjusted scores. Age adjustment resulted in weaker relationships of test scores with MRI variables; adjustment for ethnicity yielded stronger relationships. Education adjustment increased relationships with MRI variables in the combined sample and Hispanics, made no difference in Whites, but decreased some associations in African Americans. Results suggest that demographic adjustment is beneficial when demographic variables are strongly related to test scores independent of measures of brain structure, but adjustment has negative consequences when effects of demographic characteristics are mediated by brain structure.

Brain regional lesion burden and impaired mobility in the elderly

This study investigated the relationship of brain white matter (WM) lesions affecting specific neural networks with decreased mobility in ninety-nine healthy community-dwelling subjects ≥75 years old prospectively enrolled by age and mobility status. We assessed lesion burden in the genu, body and splenium of corpus callosum; anterior, superior and posterior corona radiata; anterior and posterior limbs of internal capsule; corticospinal tract; and superior longitudinal fasciculus. Burden in the splenium of corpus callosum (SCC) demonstrated the highest correlation particularly with walking speed (r=0.4, p<10(-4)), and in logistic regression it was the best regional predictor of low mobility performance. We also found that independent of mobility, corona radiata has the largest lesion burden with anterior (ACR) and posterior (PCR) aspects being the most frequently affected. The results suggest that compromised inter-hemispheric integration of visuospatial information through the SCC plays an important role in mobility impairment in the elderly. The relatively high lesion susceptibility of ACR and PCR in all subjects may obscure the importance of these lesions in mobility impairment.

Quantitative brain measurements in community-dwelling elderly persons with mild parkinsonian signs

BACKGROUND

Mild parkinsonian signs (MPS) are a marker of incident dementia. They have been linked with cerebrovascular disease, which can be evaluated using magnetic resonance imaging (MRI). Also, if MPS are a marker for developing Alzheimer-type changes, hippocampal volume on MRI might be diminished in individuals with MPS.

OBJECTIVE

To examine white matter hyperintensity (WMH) volume and total hippocampal volume in elderly individuals with and without MPS.

METHODS

Community-dwelling elderly persons in northern Manhattan (New York), New York, underwent neurologic examination and brain MRI. The WMH volume (derived from fluid-attenuated inversion recovery-weighted MRIs using a semiautomated thresholding approach) and total hippocampal volume (derived manually) were expressed relative to total cranial volume.

RESULTS

Mild parkinsonian signs were present in 111 of 666 participants (16.7%). Mean (SD) relative WMH volume was larger in participants with MPS vs those without MPS (1.70 [1.28] vs 1.17 [1.18]; P<.001). In a multivariate logistic regression analysis adjusting for age, sex, race/ethnicity, years of educational achievement, and depression, relative WMH volume was associated with MPS (odds ratio, 1.26; 95% confidence interval, 1.08-1.47; P=.004). In both unadjusted and adjusted analyses, total relative hippocampal volume was similar in participants with MPS vs those without MPS regardless of cognitive status.

CONCLUSIONS

In this MRI study of community-dwelling elderly persons, WMH volume was associated with MPS and total relative hippocampal volume was not. These data raise the possibility that vascular disease could have a role in the development of MPS.

Carotid artery atherosclerosis, MRI indices of brain ischemia, aging, and cognitive impairment: the Framingham study

BACKGROUND AND PURPOSE

Carotid atherosclerosis has been associated with increased risk of stroke and poorer cognitive performance in older adults. The relation of carotid atherosclerosis to cognitive impairment and MRI indices of ischemia and aging in midlife is less clear.

METHODS

We studied 1975 Framingham Offspring Study participants free of stroke and dementia with available carotid ultrasound, brain MRI, and neuropsychological testing. We related common and internal carotid artery intima-media thickness and internal carotid stenosis to large white matter hyperintensity (>1 SD above age-specific mean), total brain volume, hippocampal volume, silent cerebral infarcts, and neuropsychological measures of verbal memory, executive function, and nonverbal memory measures.

RESULTS

We observed that internal carotid artery intima-media thickness, but not common carotid artery intima-media thickness, was associated with higher prevalence of silent cerebral infarcts (OR, 1.21; 95% CI, 1.03-1.43; P<0.05), large white matter hyperintensity (OR, 1.19; 95% CI, 1.03-1.38; P<0.05), lower total brain volume (-0.05 per SD; P<0.05), and poorer performance in verbal memory (-0.06 per SD; P<0.05) and nonverbal memory measures (-0.08 per SD; P<0.01), but not with hippocampal volume. Internal carotid stenosis >or=25% was associated with a higher prevalence of large white matter hyperintensity (adjusted OR, 1.77; 95% CI, 1.25-2.53) and lower total brain volume (-0.11 per SD; P=0.042) but not with silent cerebral infarcts or hippocampal volume. Internal carotid stenosis >or=50% was associated with higher prevalence of silent cerebral infarcts (OR, 2.53; 95% CI, 1.17-5.44), large white matter hyperintensity (OR, 2.35; 95% CI, 1.08-5.13), and poorer performance on executive function (-0.39 per SD; P<0.05), but not with total brain volume or hippocampal volume.

CONCLUSIONS

Carotid atherosclerosis markers were associated with MRI indices of brain ischemia and aging and with cognitive impairment in a community-based sample of middle-aged adults. Our data suggest that internal carotid artery intima-media thickness may be a better marker for cognitive impairment than common carotid artery intima-media thickness.

Brain behavior relationships among African Americans, whites, and Hispanics

There is an increasing racial and ethnic diversity within the elderly population of the United States. Although increased diversity offers unique opportunities to study novel influences on aging and dementia, some aspects of racial and ethnic research have been hampered by the lack of culturally and linguistically consistent testing protocols. Structural brain imaging is commonly used to study the biology of normal aging and cognitive impairment and may therefore serve to explore potential biologic differences of cognitive impairment among racially and ethnically diverse individuals. To test this hypothesis, we recruited a cohort of approximately 400 African American, white, and Hispanic subjects with various degrees of cognitive ability. Each subject was carefully evaluated using standardized diagnostic protocols that included clinical review of brain magnetic resonance image (MRI) to arrive at a clinical diagnosis of normal cognition, mild cognitive impairment or dementia. Each MRI was then independently quantified for measures of brain, white matter hyperintensities, and hippocampal volumes by a technician blind to subject age, sex, ethnicity, race, and diagnostic category. The appearance of infarction on MRI was also rated by examining neurologists. Regression analyses were used to assess associations with various MRI measures across clinical diagnostic categories in relation to racial and ethnic differences. Hispanic subjects were, on average, significantly younger and had less years of education than African Americans or whites. Whites with dementia were significantly older than both African American and Hispanic dementia patients. Highly significant differences in MRI measures were associated with clinical diagnoses for the group as a whole after adjusting for the effects of age, sex, education, race, and ethnicity. Subsequent independent analyses by racial and ethnic status revealed consistent relationships between diagnostic category and MRI measures. Clinical diagnoses were associated with consistent differences in brain structure among a group of racially and ethnically diverse individuals. We believe these results help to validate current diagnostic assessment of individuals across a broad range of racial, ethnic, linguistic, and educational backgrounds. Moreover, interesting and potentially biologically relevant differences were found that might stimulate further research related to the understanding of dementia etiology within an increasingly racially and ethnically diverse population.

Magnetic resonance imaging traits in siblings discordant for Alzheimer disease

BACKGROUND

Magnetic resonance imaging (MRI) can aid clinical assessment of brain changes potentially correlated with Alzheimer disease (AD). MRI traits may improve our ability to identify genes associated with AD-outcomes. We evaluated semi-quantitative MRI measures as endophenotypes for genetic studies by assessing their association with AD in families from the Multi-Institutional Research in Alzheimer Genetic Epidemiology (MIRAGE) Study.

METHODS

Discordant siblings from multiple ethnicities were ascertained through a single affected proband. Semi-quantitative MRI measures were obtained for each individual. The association between continuous/ordinal MRI traits and AD were analyzed using generalized estimating equations. Medical history and Apolipoprotein E (APOE)epsilon4 status were evaluated as potential confounders.

RESULTS

Comparisons of 214 affected and 234 unaffected subjects from 229 sibships revealed that general cerebral atrophy, white matter hyperintensities (WMH), and mediotemporal atrophy differed significantly between groups (each at P < .0001) and varied by ethnicity. Age at MRI and duration of AD confounded all associations between AD and MRI traits. Among unaffected sibs, the presence of at least one APOEepsilon4 allele and MRI infarction was associated with more WMH after adjusting for age at MRI.

CONCLUSION

The strong association between MRI traits and AD suggests that MRI traits may be informative endophenotypes for basic and clinical studies of AD. In particular, WMH may be a marker of vascular disease that contributes to AD pathogenesis.

The brain in the age of old: the hippocampal formation is targeted differentially by diseases of late life

OBJECTIVE

To rely on the anatomical organization of the hippocampal formation in understanding whether and how late-life diseases such as diabetes and stroke contribute to age-related cognitive decline.

METHODS

Magnetic resonance imaging (MRI) was used to document brain infarcts and to generate high-resolution functional maps of the hippocampal formation in 240 community-based nondemented elders (mean age, 79.7 years) who received a comprehensive medical evaluation. Sixty participants had type 2 diabetes mellitus, whereas 74 had MRI-documented brain infarcts, and the first analysis was designed to pinpoint hippocampal subregions differentially linked to each disorder. Then, guided by the results, additional functional MRI studies in aging rhesus monkeys and mice were used to test proposed mechanisms of dysfunction.

RESULTS

Although both diabetes and brain infarcts were associated with hippocampal dysfunction, each was linked to separate hippocampal subregions, suggesting distinct underlying mechanisms. The hippocampal subregion linked to diabetes implicated blood glucose as a pathogenic mechanism, a hypothesis confirmed by imaging aging rhesus monkeys and a mouse model of diabetes. The hippocampal subregion linked to infarcts suggested transient hypoperfusion as a pathogenic mechanism, a hypothesis provisionally confirmed by comparing anatomical patterns across subjects with infarcts in different vascular territories.

INTERPRETATION

Taken together with previous findings, these results clarify how diseases of late life differentially target the hippocampal formation, identify elevations in blood glucose as a contributing cause of age-related memory decline, and suggest specific interventions that can preserve cognitive health.

Relevance of Iron Deposition in Deep Gray Matter Brain Structures to Cognitive and Motor Performance in Healthy Elderly Men and Women: Exploratory Findings

Iron deposition increases in normal aging, has its greatest presence in structures of the extrapyramidal system, and may contribute to functional decline. MR imaging provides a method for indexing iron deposition in brain structures because of iron's ferromagnetic properties, which interact with the MRI environment to cause signal intensity attenuation that is quantifiable by comparing images collected at 1.5 and 3.0 T. We tested functional correlates of an MR-based iron index in 10 healthy, elderly individuals previously reported to have a higher iron burden in the putamen and lower in the thalamus than young individuals. Lower scores on the Dementia Rating Scale and longer reaction times on a two-choice attention test correlated with higher iron estimates in the caudate nucleus and putamen; poorer Mini-Mental State Examination and Digit Symbol scores correlated with lower iron estimates in the thalamus. Further analyses based on multiple regression, which considered regional FDRI estimates and volume measures as predictors of performance, identified iron but not the sampled volume as the unique predictor in each case. These exploratory correlations suggest a substrate of performance degradation in aging and have implications for regional signal darkening in an array of MR-based imaging protocols.

Association of matrix metalloproteinases with MRI indices of brain ischemia and aging

Magnetic resonance imaging (MRI) findings of large white matter hyperintensities (LWMH), decreased brain volume and silent cerebral infarcts (SCI) are subclinical indices of brain ischemia and aging. Although the pathophysiology of these findings remains uncertain, extracellular matrix (ECM) remodeling, a process regulated by matrix metalloproteinases (MMPs) and their inhibitors (TIMPs), may be implicated. We evaluated the cross-sectional relations of circulating MMP-9 and TIMP-1 to these MRI indices in 583 stroke and dementia-free, Framingham Offspring participants (mean age 57 years, 58% women). Using multivariable regression MMP-9 (detectable versus non-detectable) and TIMP-1 (modeled as sex-specific quartiles) were related to LWMH (>1S.D. above age-specific mean; yes/no), SCI (yes/no) and total brain volume (ratio of parenchymal to intracranial volume, TCBVr). Mean TCBVr was 0.78 (S.D. 0.03), 13% of subjects had LWMH and 12% had SCI. Detectable MMP-9 was associated with higher prevalence of LWMH (OR 2.09, 95%confidence interval (CI) 1.00-4.37), but not with TCBVr. TIMP-1 was associated with a high prevalence of LWMH (OR for Q4 versus Q1-3: 1.83, 95%CI 1.06-3.18) and with lower mean TCBVr (Q4 associated with 0.17 S.D. units lower value relative to Q1-3; p=0.04). Neither biomarker was associated with SCI. Our findings are preliminary but if confirmed in further studies, suggest a pathophysiological role for the MMP/TIMP pathway in processes of brain ischemia and aging.