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1.  Carotid Artery Plaque Thickness is Associated with Increased Serum Calcium Levels: the Northern Manhattan Study 
Atherosclerosis  2006;194(2):426-432.
Elevated serum calcium concentrations are associated with vascular calcification and cardiovascular disease. It is unknown whether there is a relationship between high-normal serum calcium levels and sub-clinical vascular effects. We investigated the association between serum calcium and carotid plaque thickness, a powerful early predictor of clinical coronary and cerebrovascular events.
Epidemiological study of 1194 subjects from the Northern Manhattan Study cohort, a prospective community-based study designed to investigate risk factors for vascular disease in different race-ethnic groups.
Subjects with carotid plaque had higher corrected serum calcium levels within the normal range than those without carotid plaque (2.21 ± .09 vs. 2.19 ± .09 mmol/L, p<0.002). The relationship between carotid plaque and serum calcium persisted after adjustment for traditional cardiovascular risk factors. Subjects in the top quintile of maximal carotid plaque thickness (≥ 1.7 mm) were more likely to be in the highest quintile of serum calcium level (OR=1.64, 95% CI=1.17 to 2.29, p< 0.004). The interaction of age and corrected serum calcium was the most significant predictor of carotid plaque thickness when traditional vascular risk factors were considered (p<0.001).
Serum calcium levels in a multi-ethnic population of older men and women were positively associated with carotid plaque thickness, a powerful early predictor of clinical coronary and cerebrovascular events.
PMCID: PMC3138549  PMID: 17030035
2.  Infectious Burden and Risk of Stroke: The Northern Manhattan Study 
Archives of neurology  2009;67(1):33-38.
Common infections may be associated with stroke risk, though no single infection is likely a major independent predictor.
To determine the association between a composite measure of serologies to common infections (Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, Herpes Simplex Virus 1 and 2) and stroke risk in a prospective cohort study.
Prospective cohort followed longitudinally for median 8 years.
Randomly selected stroke-free participants from a multiethnic urban community.
Northern Manhattan Study (NOMAS).
Main Outcome measure
Incident stroke and other vascular events.
All five infectious serologies were available from baseline samples in 1625 participants (mean age 68.5 ± 10.1 years; 64.9% women). Cox proportional hazards models were used to estimate associations of each positive serology with stroke. Individual parameter estimates were then combined into a weighted index of infectious burden (IB) and used to calculate hazard ratios and confidence intervals (HR, 95% CI) for association with risk of stroke and other outcomes, adjusted for risk factors. Each individual infection was positively though not significantly associated with stroke risk after adjusting for other risk factors. The IB index was associated with an increased risk of all strokes (adjusted HR per standard deviation 1.39, 95% CI 1.02–1.90) after adjusting for demographics and risk factors. Results were similar after excluding those with coronary disease (adjusted HR 1.50, 95% CI 1.05–2.13) and adjusting for inflammatory biomarkers.
A quantitative weighted index of infectious burden was associated with risk of first stroke in this cohort. Future studies are needed to confirm these findings and to further define optimal measures of IB as a stroke risk factor.
PMCID: PMC2830860  PMID: 19901154
3.  Infectious Burden and Carotid Plaque Thickness: The Northern Manhattan Study 
The overall burden of prior infections may contribute to atherosclerosis and stroke risk. We hypothesized that serological evidence of common infections would be associated with carotid plaque thickness in a multi-ethnic cohort.
Antibody titers to five common infectious microorganisms (i.e. Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, and herpesvirus 1 and 2) were measured among stroke-free community participants, and a weighted index of infectious burden (IB) was calculated based on Cox models previously derived from for the association of each infection with stroke risk. High-resolution carotid duplex Doppler studies were used to assess maximum carotid plaque thickness (MCPT). Weighted least squares regression was used to measure the association between IB and MCPT after adjusting for other risk factors.
Serological results for all five infectious organisms were available in 861 participants with MCPT measurements available (mean age 67.2+/−9.6 yrs). Each individual infection was associated with stroke risk after adjusting for other risk factors. The IB index (n=861) had a mean of 1.00 ± standard deviation 0.35, median 1.08. Plaque was present in 52% of participants (mean 0.90+/−1.04 mm). IB was associated with MCPT (adjusted increase in MCPT 0.09 mm, 95% confidence interval 0.03–0.15 mm, per standard deviation increase of IB).
A quantitative weighted index of infectious burden, derived from the magnitude of association of individual infections with stroke, was associated with carotid plaque thickness in this multi-ethnic cohort. These results lend support to the notion that past or chronic exposure to common infections, perhaps by exacerbating inflammation, contributes to atherosclerosis. Future studies are needed to confirm this hypothesis and to define optimal measures of infectious burden as a vascular risk factor.
PMCID: PMC2830875  PMID: 20075350
4.  Metabolic Syndrome, Endothelial Dysfunction, and Risk of Cardiovascular Events: the Northern Manhattan Study 
American heart journal  2008;156(2):405-410.
Metabolic syndrome (MetS) predisposes to cardiovascular disease. Endothelial dysfunction is thought to be an important factor in the pathogenesis of atherosclerosis. We tested the hypothesis that both MetS and endothelial dysfunction are vascular risk factors and provide additive prognostic values in predicting cardiovascular events in a multi-ethnic community sample.
The study population consisted of 819 subjects (467 female, mean age 66.5±8.8 years, 66% Hispanic) enrolled in the Northern Manhattan Study. MetS was defined using the revised Adult Treatment Panel III criteria. Brachial artery flow-mediated dilation (FMD) was measured using high-resolution ultrasound. Endothelial dysfunction was defined as FMD < 8.44% (lower three quartiles). Cox proportional hazards models were used to assess the effect of MetS and endothelial dysfunction on risk of cardiovascular events.
During 81±21 months of follow-up, events occurred in 84 subjects. MetS was independently associated with cardiovascular events in a multivariate model including cardiovascular risk factors (adjusted HR 2.08, 95% CI 1.27–3.40). Subjects with both MetS and endothelial dysfunction were at higher risk for cardiovascular events than those with either one of them alone (adjusted HR 2.60, 95% CI 1.14–5.92).
MetS is associated with incident cardiovascular events. Combined use of MetS and FMD identifies those who are at higher risk of cardiovascular events. MetS and non-invasive FMD testing can be used concurrently for cardiovascular risk prediction.
PMCID: PMC2597726  PMID: 18657678
5.  Carotid Intima-Media Thickness Is Associated With Allelic Variants of Stromelysin-1, Interleukin-6, and Hepatic Lipase Genes The Northern Manhattan Prospective Cohort Study 
Background and Purpose
Atherosclerosis is a complex disorder with hereditary and environmental causes. Carotid artery intima-media wall thickness (IMT) is a useful measure of atherosclerosis. The objective of this study was to determine the association between carotid IMT and functional promoter variants of stromelysin-1 (MMP3: −1612 5A>6A), interleukin-6 (IL6: −174G>C), and hepatic lipase (HL: −480C>T) genes.
B-mode carotid ultrasound was performed among 87 subjects (mean age, 70 ± 12 years; 55% women; 60% Caribbean-Hispanic, 25% black, and 13% white) from the Northern Manhattan Prospective Cohort Study. Carotid IMT was calculated as a composite measure (mean of the maximum IMT in the bifurcation, the common carotid artery, and the internal carotid artery).
For all polymorphisms, genotype distribution was not significantly different from Hardy-Weinberg equilibrium. The frequencies of the rare alleles were as follows: MMP3 −1612 5A>6A, 0.31 (95% CI, 0.25 to 0.39); IL6 −174 G>C, 0.20 (95% CI, 0.13 to 0.25); and HL −480 C>T, 0.45 (95% CI, 0.35 to 0.50). Carotid IMT in the sample was 0.78±0.18 mm. Subjects with the MMP3 genotype 6A6A had 8% greater mean carotid IMT than the other MMP3 genotypes combined (0.95±0.17 versus 0.87±0.15 mm; P=0.04). Subjects with the IL6 genotype GG had 11% greater IMT (0.85±0.17 versus 0.76±0.16 mm; P=0.03), and those with the HL genotype CC had 13% greater IMT (0.87±20 versus 0.76±0.18 mm; P=0.02) than the other genotypes combined. Adjustment for other risk factors did not change these associations.
Carotid IMT is higher among subjects homozygous for functional variants in genes related to matrix deposition (MMP3 −16126A), inflammation (IL6 −174G), and lipid metabolism (HL −480C). These associations were independent of race-ethnicity and some environmental exposures. Further studies are needed to confirm these genotype-phenotype associations.
PMCID: PMC2692936  PMID: 11988625
genetics; interleukin-6; intima-media thickness; lipase; stromelysin 1; ultrasonography
7.  Tumor Necrosis Factor Receptor Levels Are Associated With Carotid Atherosclerosis 
Background and Purpose
Recent evidence suggests that atherosclerosis is an inflammatory condition. Serum levels of inflammatory markers may serve as measures of the severity of atherosclerosis and risk of stroke. We sought to determine whether tumor necrosis factor-α (TNF-α) and TNF receptor levels are associated with carotid plaque thickness.
The Northern Manhattan Stroke Study is a community-based study of stroke risk factors. For this cross-sectional analysis, inflammatory marker levels, including TNF-α and TNF receptors 1 and 2, were measured by immunoassay in stroke-free community subjects undergoing carotid duplex Doppler ultrasound. Maximal carotid plaque thickness (MCPT) was measured for each subject. Analyses were stratified by age <70 and ≥70 years. Simple and multiple linear regression analyses were used to calculate the association between marker levels and MCPT. Multiple logistic regression was used to calculate odds ratios and 95% CIs for the association of inflammatory markers with MCPT ≥1.5 mm (>75th percentile), after adjustment for demographic and potential medical confounding factors.
The mean age of the 279 subjects was 67.6±8.5 years; 49% were men; 63% were Hispanic, 17% black, and 17% white. Mean values for TNF-α and its receptors were as follows: TNF-α, 1.88±3.97 ng/mL; TNF receptor 1, 2.21±0.99 ng/mL; and TNF receptor 2, 4.85±2.23 ng/mL. Mean MCPT was elevated in those in the highest quartiles compared with lowest quartiles of TNF receptor 1 and 2 (1.24 versus 0.79 mm and 1.23 versus 0.80 mm, respectively). Among those aged <70 years, TNF receptor 1 and 2 were associated with an increase in MCPT (mean difference=0.36 mm, P=0.01 for TNF receptor 1 and mean difference=0.10 mm, P=0.04 for TNF receptor 2). After adjustment for sex, race-ethnicity, hypertension, diabetes mellitus, LDL cholesterol, smoking, and body mass index, associations remained (mean difference=0.36 mm, P=0.001 for TNF receptor 1 and mean difference=0.09 mm, P=0.051 for TNF receptor 2). There was no association for TNF receptors in those aged ≥70 years old and no association for TNF-α in either age group. Among those aged ≥70 years, each unit increase in TNF receptor level increased the odds of the participant’s having MCPT ≥1.5 mm (adjusted odds ratio=4.7; 95% CI, 1.7 to 15.4 for TNF receptor 1; odds ratio=1.9; 95% CI, 1.3 to 2.9 for TNF receptor 2).
Relative elevation in TNF receptor levels, but not TNF-α, is associated with carotid atherosclerosis among individuals aged <70 years in this multiethnic, urban population. Chronic subclinical infection or inflammation may account for this association, and modification of these inflammatory pathways may provide a novel approach to stroke prevention.
PMCID: PMC2677183  PMID: 11779885
atherosclerosis; cerebrovascular disorders; epidemiology; risk factors
8.  Left Ventricular Systolic Dysfunction and the Risk of Ischemic Stroke in a Multiethnic Population 
Background and Purpose
Left ventricular dysfunction (LVD) is associated with cardiovascular mortality. Its association with ischemic stroke has been mainly documented after myocardial infarction. The stroke risk associated with LVD, especially of mild degree, in the general population is unclear. The purpose of this study was to evaluate the relationship between LVD and ischemic stroke in a multiethnic cohort.
LV systolic function was assessed by transthoracic 2-dimensional echocardiography in a subset of subjects from the Northern Manhattan Study (NOMAS), 270 patients with first ischemic stroke and 288 age-, gender- and race-matched community controls. LV ejection fraction was measured by a simplified cylinder-hemiellipsoid formula, and categorized as normal (>50%), mildly (41% to 50%), moderately (31% to 40%) or severely (≤30%) decreased. The association between impaired ejection fraction and ischemic stroke was evaluated by logistic regression analysis after adjustment for established stroke risk factors.
LVD of any degree was more frequent in stroke patients (24.1%) than in controls (4.9%; P<0.0001), as was moderate/severe LVD (13.3% versus 2.4%; P<0.001). A decreased ejection fraction was associated with ischemic stroke even after adjusting for other stroke risk factors. The adjusted odds ratio for any degree of LVD was 3.92 (95% CI, 1.93 to 7.97). The adjusted odds ratio for mild LVD was 3.96 (95% CI, 1.56 to 10.01) and for moderate/severe LVD 3.88 (95% CI, 1.45 to 10.39). The association between LVD of any degree and stroke was present in all age, gender and race-ethnicity subgroups.
LVD, even of mild degree, is independently associated with an increased risk of ischemic stroke. The assessment of LV function should be considered in the assessment of the stroke risk.
PMCID: PMC2677017  PMID: 16741172
cerebrovascular disorders; echocardiography; left ventricular function
9.  Metabolic Syndrome and Ischemic Stroke Risk Northern Manhattan Study 
Background and Purpose
More than 47 million individuals in the United States meet the criteria for the metabolic syndrome. The relation between the metabolic syndrome and stroke risk in multiethnic populations has not been well characterized.
As part of the Northern Manhattan Study, 3298 stroke-free community residents were prospectively followed up for a mean of 6.4 years. The metabolic syndrome was defined according to guidelines established by the National Cholesterol Education Program Adult Treatment Panel III. Cox proportional-hazards models were used to calculate hazard ratios (HRs) and 95% CIs for ischemic stroke and vascular events (ischemic stroke, myocardial infarction, or vascular death). The etiologic fraction estimates the proportion of events attributable to the metabolic syndrome.
More than 44% of the cohort had the metabolic syndrome (48% of women vs 38% of men, P<0.0001), which was more prevalent among Hispanics (50%) than whites (39%) or blacks (37%). The metabolic syndrome was associated with increased risk of stroke (HR=1.5; 95% CI, 1.1 to 2.2) and vascular events (HR=1.6; 95% CI, 1.3 to 2.0) after adjustment for sociodemographic and risk factors. The effect of the metabolic syndrome on stroke risk was greater among women (HR=2.0; 95% CI, 1.3 to 3.1) than men (HR=1.1; 95% CI, 0.6 to 1.9) and among Hispanics (HR=2.0; 95% CI, 1.2 to 3.4) compared with blacks and whites. The etiologic fraction estimates suggest that elimination of the metabolic syndrome would result in a 19% reduction in overall stroke, a 30% reduction of stroke in women; and a 35% reduction of stroke among Hispanics.
The metabolic syndrome is an important risk factor for ischemic stroke, with differential effects by sex and race/ethnicity.
PMCID: PMC2677015  PMID: 18063821
epidemiology; ischemic stroke; metabolic syndrome; race/ethnicity; risk factors; sex
10.  Transient Ischemic Attack Before Nonlacunar Ischemic Stroke in the Elderly 
Several studies suggest transient ischemic attack (TIA) may be neuroprotective against ischemic stroke analogous to preinfarction angina's protection against acute myocardial infarction. However, this protective ischemic preconditioning-like effect may not be present in all ages, especially among the elderly. The purpose of this study was to determine the neuroprotective effect of TIAs (clinical equivalent of cerebral ischemic preconditioning) to neurologic damage after cerebral ischemic injury in patients over 65 years of age.
We reviewed the medical charts of patients with ischemic stroke for presence of TIAs within 72 hours before stroke onset. Stroke severity was evaluated by the National Institutes of Health Stroke Scale and disability by a modified Rankin scale.
We evaluated 203 patients (≥65 years) with diagnosis of acute ischemic stroke and categorized them according to the presence (n = 42, 21%) or absence (n = 161, 79%) of TIAs within 72 hours of stroke onset. Patients were monitored until discharged from the hospital (length of hospital stay 14.5 ± 4.8 days). No significant differences in the National Institutes of Health Stroke Scale and modified Rankin scale scores were observed between those patients with TIAs and those without TIAs present before stroke onset at admission or discharge.
These results suggest that the neuroprotective mechanism of cerebral ischemic preconditioning may not be present or functional in the elderly.
PMCID: PMC2676578  PMID: 18755403
Cerebral ischemic preconditioning; transient ischemic attack; elderly; stroke
11.  Genetic contribution to brachial artery flow-mediated dilation: The Northern Manhattan Family Study 
Atherosclerosis  2007;197(1):212-216.
Brachial artery flow-mediated dilation (FMD) is a non-invasive measure of endothelial function. Endothelial dysfunction has been associated with traditional vascular risk factors and increased risk of cardiovascular disease. The importance of genetic contribution to FMD and baseline brachial artery diameter has not been shown in Hispanic populations. The purpose of this study was to estimate the heritability of FMD.
Flow mediated dilation and brachial artery diameter were measured in a subset of Caribbean Hispanic families from the ongoing Northern Manhattan Family Study (NOMAFS), which studies the contribution of genetics to stroke and cardiovascular risk factors. The age- and sex-adjusted heritability of FMD was estimated using variance component methods.
The current data include 620 subjects (97 probands and 523 relatives) from 97 families. The age and sex-adjusted heritability of brachial artery diameter was 0.57 (p < 0.01). The age- and sex-adjusted heritability of FMD was 0.20 (p = 0.01). After additional adjustment for systolic and diastolic blood pressure, body mass index, smoking, lipid, diabetes mellitus, medication, and baseline brachial artery diameter, the heritability of FMD was 0.17 (p = 0.01).
We found modest heritability of FMD. FMD might be a reasonable phenotype for further investigation of genetic contribution to atherosclerosis.
PMCID: PMC2268620  PMID: 17462653
Flow-mediated dilation; Endothelial function; Atherosclerosis; Heritability; Genetics
12.  Design of a Family Study Among High-Risk Caribbean Hispanics: The Northern Manhattan Family Study 
Ethnicity & disease  2007;17(2):351-357.
Stroke continues to kill disproportionately more Blacks and Hispanics than Whites in the United States. Racial/ethnic variations in the incidence of stroke and prevalence of stroke risk factors are probably explained by both genetic and environmental influences. Family studies can help identify genetic predisposition to stroke and potential stroke precursors. Few studies have evaluated the heritability of these stroke risk factors among non-White populations, and none have focused on Caribbean Hispanic populations. The aim of the Northern Manhattan Family Study (NOMAFS) is to investigate the gene-environment interaction of stroke risk factors among Caribbean Hispanics. The unique recruitment and methodologic approaches used in this study are relevant to the design and conduct of genetic aggregation studies to investigate complex genetic disorders in non-White populations. The aim of this paper is to describe the NOMAFS and report enrollment and characteristics of the participants. The NO-MAFS will provide a data resource for the exploration of the genetic determinants of highly heritable stroke precursor phenotypes that are less complex than the stroke phenotype. Understanding the gene environment interaction is the critical next step toward the development of new and unique approaches to disease prevention and interventions.
PMCID: PMC2556080  PMID: 17682370
Stroke; Hispanic; Genetics
13.  Multiple genetic determinants of plasma lipid levels in Caribbean Hispanics 
Clinical biochemistry  2007;41(4-5):306-312.
To identify candidate genes in relation to plasma lipid levels in Caribbean Hispanics.
Design and methods:
A total of 114 single nucleotide polymorphisms (SNPs) at 17 lipid-related genes were genotyped in 477 Caribbean Hispanics from the Northern Manhattan Study (NOMAS). Analyses for each SNP and haplotype were performed to evaluate the associations with four lipid traits: high- and low-density lipoprotein cholesterol (HDL-C, LDL-C), triglyceride (TG) and total cholesterol (TC).
We identified 19 SNPs at 10 genes that were significantly related to lipids (p<0.01), including nine involved in the reverse cholesterol transport pathway, and one involved in bile acid synthesis. Three genes, namely the apolipoprotein A5, apolipoprotein B and cytochrome p450 polypeptide 7A1 genes, accounted for the largest proportion of variation in HDL-C/TG, TC and LDL-C respectively.
The cumulative effects of multiple genetic variants led to a substantially better prediction of inter-individual variations in lipid levels.
PMCID: PMC2366941  PMID: 18078817
Gene; Single nucleotide polymorphisms; Reverses cholesterol transport pathway; Lipids; Haplotype
14.  Genetic and Environmental Contributions to Carotid Intima-Media Thickness and Obesity Phenotypes in the Northern Manhattan Family Study 
Background and Purpose
Both carotid intima-media thickness (IMT) and obesity are independent determinants of stroke and cardiovascular disease. The prevalence of obesity is higher in Hispanics. The genetic basis of IMT and obesity has not been well-characterized in Caribbean Hispanics. The purpose of this study was to examine the genetic and environmental contributions to IMT and obesity in this population.
The data included 440 subjects from 77 Caribbean Hispanic families. Mean IMT and maximum IMT were measured in the internal carotid artery, common carotid artery, and carotid bifurcation. The total IMT was calculated as the mean value of IMT at all segments. Obesity phenotypes included body mass index (BMI), waist circumference, waist-to-hip ratio (WHR), and skin-fold thickness. Variance component methods were used to estimate age-adjusted and sex-adjusted heritability. Bivariate analyses were conducted to test for genetic and environmental correlations between IMT and obesity.
Heritabilities for IMT ranged from 9% to 40%, with the highest for total maximum IMT and lowest for internal carotid artery maximum IMT. Heritabilities for BMI, waist circumference, WHR, and skin-fold thickness were 44%, 47%, 5%, and 36%, respectively. There were significant genetic, but not environmental, correlations between IMT and BMI, waist circumference, and skin-fold thickness. There were no genetic or environmental correlations between IMT and WHR.
We found a substantial genetic contribution to IMT, BMI, waist circumference, and skin-fold thickness. Obesity and IMT may share common genetic factors. Future gene mapping studies are warranted to identify genes predisposing to IMT and obesity in this population.
PMCID: PMC1325223  PMID: 15331789
carotid arteries; genetics; obesity; stroke
15.  Heritability of Carotid Artery Distensibility in Hispanics The Northern Manhattan Family Study 
Background and Purpose
Reduced arterial distensibility has been introduced as a novel risk factor for atherosclerosis. The importance of the genetic contribution to variation in distensibility is largely unknown. The purpose of this study was to estimate heritability of carotid distensibility.
The ongoing Northern Manhattan Family Study recruits high-risk Caribbean Hispanic families to study genetic effects on stroke/cardiovascular risk factors. The distensibility metrics (strain, stiffness, distensibility, and elastic modulus) were measured from the right common carotid artery, and the heritability for each was estimated. Variance component methods were used to estimate age- and sex-adjusted heritability. Correlations were calculated to evaluate the relationship between distensibility phenotypes and intimamedia thickness (IMT) at each carotid segment.
The current data included 88 probands and 605 relatives from 88 families. Age- and sex-adjusted heritability was 25% for strain, 17% for distensibility, 20% for stiffness, and 20% for elastic modulus. Without adjustment for covariates, strong correlations were found between distensibility metrics and IMT: the absolute values of correlation coefficients were between 0.2 and 0.5, and all P values were <0.001. However, the correlation coefficients were reduced substantially after adjusting for age and sex.
These results suggested that genetic factors explained a moderate proportion of the variability of carotid distensibility. The correlations between distensibility and IMT were mainly attributable to age and sex effects. The regulation of carotid distensibility and IMT may reflect different underlying genetic and environmental mechanisms.
PMCID: PMC1289274  PMID: 16224080
atherosclerosis; carotid arteries; genetics

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