Carotid plaque area and intima-media thickness in prediction of first-ever ischemic stroke: a 10-year follow-up of 6584 men and women: the Tromsø Study

Carotid intima-media thickness and plaque in cardiovascular risk assessment

Carotid intima-media thickness (CIMT) has been shown to predict cardiovascular (CV) risk in multiple large studies. Careful evaluation of CIMT studies reveals discrepancies in the comprehensiveness with which CIMT is assessed-the number of carotid segments evaluated (common carotid artery [CCA], internal carotid artery [ICA], or the carotid bulb), the type of measurements made (mean or maximum of single measurements, mean of the mean, or mean of the maximum for multiple measurements), the number of imaging angles used, whether plaques were included in the intima-media thickness (IMT) measurement, the report of adjusted or unadjusted models, risk association versus risk prediction, and the arbitrary cutoff points for CIMT and for plaque to predict risk. Measuring the far wall of the CCA was shown to be the least variable method for assessing IMT. However, meta-analyses suggest that CCA-IMT alone only minimally improves predictive power beyond traditional risk factors, whereas inclusion of the carotid bulb and ICA-IMT improves prediction of both cardiac risk and stroke risk. Carotid plaque appears to be a more powerful predictor of CV risk compared with CIMT alone. Quantitative measures of plaques such as plaque number, plaque thickness, plaque area, and 3-dimensional assessment of plaque volume appear to be progressively more sensitive in predicting CV risk than mere assessment of plaque presence. Limited data show that plaque characteristics including plaque vascularity may improve CV disease risk stratification further. IMT measurement at the CCA, carotid bulb, and ICA that allows inclusion of plaque in the IMT measurement or CCA-IMT measurement along with plaque assessment in all carotid segments is emerging as the focus of carotid artery ultrasound imaging for CV risk prediction.

Intima modifier locus 2 controls endothelial cell activation and vascular permeability

Carotid intima formation is a significant risk factor for cardiovascular disease. C3H/FeJ (C3H/F) and SJL/J (SJL) inbred mouse strains differ in susceptibility to immune and vascular traits. Using a congenic approach we demonstrated that the Intima modifier 2 (Im2) locus on chromosome 11 regulates leukocyte infiltration. We sought to determine whether inflammation was due to changes in circulating immune cells or activation of vascular wall cells in genetically pure Im2 (C3H/F.SJL.11.1) mice. Complete blood counts showed no differences in circulating monocytes between C3H/F and C3H/F.SJL.11.1 compared with SJL mice. Aortic vascular cell adhesion molecule-1 (VCAM-1) total protein levels were dramatically increased in SJL and C3H/F.SJL.11.1 compared with C3H/F mice. Immunostaining of aortic endothelial cells (EC) showed a significant increase in VCAM-1 expression in SJL and C3H/F.SJL.11.1 compared with C3H/F under steady flow conditions. Immunostaining of EC membranes revealed a significant decrease in EC size in SJL and C3H/F.SJL.11.1 vs. C3H/F in regions of disturbed flow. Vascular permeability was significantly higher in C3H/F.SJL.11.1 compared with C3H/F. Our results indicate that Im2 regulation of leukocyte infiltration is mediated by EC inflammation and permeability. RNA sequencing and pathway analyses comparing genes in the Im2 locus to C3H/F provide insight into candidate genes that regulate vascular wall inflammation and permeability highlighting important genetic mechanisms that control vascular intima in response to injury.

Novel genetic variants modify the effect of smoking on carotid plaque burden in Hispanics

BACKGROUND AND PURPOSE

Smoking greatly increases the risk of atherosclerotic plaque and the effect may vary from individual to individual. A genome-wide scan was performed for smoking×single nucleotide polymorphism (SNP) interactions on carotid plaque burden (CPB) to identify the potential genetic moderators in Hispanics.

METHODS

Carotid B-mode ultrasonography and genotyping by the Affymetrix 6.0 chip were performed in a discovery sample of 665 Caribbean Hispanics, followed by replication analyses in 264 Caribbean Hispanics. CPB was expressed as the sum of plaque areas over the segments in common and internal carotid arteries and bifurcation. Smoking was classified as 0, <20, and ≥20 cigarette pack-years. Assuming an additive genetic model, regression analysis was conducted to test for smoking×SNP interaction on the cube root transformed CPB while controlling for age, sex, and the top 3 principal components of ancestry.

RESULTS

Two SNPs showed a significant interaction with smoking on CPB with the similar effects in both discovery (P<1.0E-5) and replication (P<0.05) populations. Specifically, for SNP rs10205487 within MXD1, more smoking was significantly associated with greater CPB in A allele carriers (beta±SE: 0.24±0.08, P=0.005 in AG carriers; beta±SE: 0.48±0.12, P=0.0002 in AA carriers) but not in GG (P=0.06). For SNP rs7001413 within LY96 and JPH1, more smoking was significantly associated with greater CPB in GG carriers (beta±SE: 0.24±0.06, P=6.8E-5) but not in T carriers (P=0.06).

CONCLUSIONS

Our study suggests that genetic variants may modulate the effect of smoking on CPB and highlights several genes for further investigation of their role in atherosclerosis, especially in smoking population.

SPARKLE (Subtypes of Ischaemic Stroke Classification System), incorporating measurement of carotid plaque burden: a new validated tool for the classification of ischemic stroke subtypes

BACKGROUND

Previous classification systems of acute ischemic stroke (Causative Classification System, CCS, of acute ischemic stroke, Trial of Org 10172 in Acute Stroke Treatment, TOAST) established the diagnosis of large artery disease (LAD) based on the presence or absence of carotid stenosis. However, carotid plaque burden is a stronger predictor of cardiovascular risk than stenosis. Our objective was to update definitions of ischemic stroke subtypes to improve the detection of LAD and to assess the validity and reliability of a new classification system: SPARKLE (Subtypes of Ischaemic Stroke Classification System).

METHODS

In a retrospective review of clinical research data, we compared three stroke subtype classifications: CCS, TOAST and SPARKLE. We analyzed a random sample of 275 patients presenting with minor stroke or transient ischemic attack (TIA) in an Urgent TIA Clinic in London, Ont., Canada, between 2002 and 2012.

RESULTS

There was substantial overall agreement between SPARKLE and CCS (κ = 0.75), with significant differences in the rate of detection of LAD, cardioembolic and undetermined causes of stroke or TIA. The inter-rater reliability of SPARKLE was substantial (κ = 0.76) and the intra-rater reliability was excellent (κ = 0.91).

CONCLUSION

SPARKLE is a valid and reliable classification system, providing advantages compared to CCS and TOAST. The incorporation of plaque burden into the classification of LAD increases the proportion of cases attributable to LAD and reduces the proportion classified as being of 'undetermined' etiology.

Five-year change in systolic blood pressure is independently associated with carotid atherosclerosis progression: a population-based cohort study

The aim of this study was to investigate whether long-term changes in traditional risk factors affect the progression of carotid atherosclerosis in a Chinese population. This study included 1590 individuals (aged 56.9±8.1 years) with no evidence of carotid plaque at baseline (2002). In 2007, these individuals completed the second risk factors survey and underwent carotid plaque measurement. The incidence of carotid plaque and the total plaque area of maximum plaques (TPA) were used to evaluate the progression of carotid atherosclerosis. In addition to baseline age, systolic blood pressure (SBP), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), common carotid intima-media thickness (CIMT) and current smoking, a 5-year change in SBP was also associated with the incidence of carotid plaque (odds ratio=1.01, 95% confidence interval: 1.01-1.02, P=0.029). Furthermore, multiple linear regression analysis revealed that a 5-year change in SBP had a linear association with TPA after adjusting for baseline risk factors (standardized regression coefficient=0.071, P=0.014). TPA increased both by increasing baseline SBP and by a 5-year SBP change when adjusted for sex, baseline age, TC, HDL-C, CIMT and current smoking (P for trend <0.001 and 0.004). Our study demonstrates that a 5-year change in SBP is independently associated with the progression of carotid atherosclerosis in the Chinese population. These findings underline the importance of early detection and control of SBP for the prevention of atherosclerosis progression. The progression of atherosclerosis is not only associated with hypertension but can also progress silently with the development of SBP.

Incident stroke is associated with common carotid artery diameter and not common carotid artery intima-media thickness

BACKGROUND AND PURPOSE

The common carotid artery interadventitial diameter is measured on ultrasound images as the distance between the media-adventitia interfaces of the near and far walls. It is associated with common carotid intima-media thickness (IMT) and left ventricular mass and might therefore also have an association with incident stroke.

METHODS

We studied 6255 individuals free of coronary heart disease and stroke at baseline with mean age of 62.2 years (47.3% men), members of a multiethnic community-based cohort of whites, blacks, Hispanics, and Chinese. Ischemic stroke events were centrally adjudicated. Common carotid artery interadventitial diameter and IMT were measured. Cases with incident atrial fibrillation (n=385) were excluded. Multivariable Cox proportional hazards models were generated with time to ischemic event as outcome, adjusting for risk factors.

RESULTS

There were 115 first-time ischemic strokes at 7.8 years of follow-up. Common carotid artery interadventitial diameter was a significant predictor of ischemic stroke (hazard ratio, 1.86; 95% confidence interval, 1.59-2.17 per millimeter) and remained so after adjustment for risk factors and common carotid IMT with a hazard ratio of 1.52/mm (95% confidence interval, 1.22-1.88). Common carotid IMT was not an independent predictor after adjustment (hazard ratio, 0.14; 95% confidence interval, 0.14-1.19).

CONCLUSIONS

Although common carotid IMT is not associated with stroke, interadventitial diameter of the common carotid artery is independently associated with first-time incident ischemic stroke even after adjusting for IMT. Our hypothesis that this is in part attributable to the effects of exposure to blood pressure needs confirmation by other studies.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00063440.

Carotid artery atherosclerosis among 65-year-old Swedish men - a population-based screening study

OBJECTIVE

There are limited contemporary epidemiological data on the prevalence of carotid atherosclerosis in the general population. The aim was to determine the prevalence of and risk factors associated with carotid artery atherosclerosis among 65-year-old men.

METHODS

This was a population-based screening study. All 65-year-old men in the County of Uppsala, Sweden, who attended screening for abdominal aortic aneurysm (AAA) 2007-2009, were invited for duplex scanning of the carotid arteries.

RESULTS

Of 4801 men invited, 4657 (97%) accepted. Carotid plaques (>2 × 6 mm) were observed in 1169 (25%) men, 94 (2.0%) had carotid stenoses (50-99%), and 15 (0.3%) had occluded carotid arteries. In a multivariate logistic regression model, smoking (OR 1.7, 95% CI 1.5-1.9), hypertension (1.5, 95% CI 1.3-1.7), diabetes mellitus (1.2, 95% CI 1.0-1.5), and coronary artery disease (1.5, 95% CI 1.3-1.8) were associated with prevalence of carotid atherosclerosis (plaque and/or stenosis). The use of antiplatelet agents and statins in participants with a carotid plaque was 20% and 29%, respectively. The corresponding figures in participants with a stenosis were 42% and 41%.

CONCLUSIONS

This study offers contemporary data on the prevalence of carotid atherosclerosis in a population-based cohort of 65-year-old men. Most of those at risk had no other clinical manifestation of atherosclerosis, and therefore had no secondary prevention.

Impact of Incident Venous Thromboembolism on Risk of Arterial Thrombotic Diseases

Background—

Growing evidence supports an association between venous thromboembolism (VTE) and arterial thrombotic diseases (ie, myocardial infarction and ischemic stroke). We aimed to study the association between VTE and future arterial events and to determine the population attributable risk of arterial events by VTE in a large prospective cohort recruited from the general population.

Methods and Results—

In 1994 to 1995 and 1993 to 1997, 81 687 subjects were included in the Tromsø Study and in the Diet, Cancer and Health Study and followed up to the date of incident venous and arterial events (myocardial infarction or ischemic stroke), death or migration, or to the end of the study period (2010 and 2008, respectively). There were 1208 cases of VTE and 90 subsequent arterial events during a median follow-up of 12.2 years. An association between VTE and future arterial events was found in all women and men aged <65 years but not in men aged >65 years. Women <65 years old with VTE had 3.3-fold higher risk of arterial disease (adjusted hazard ratio, 3.28; 95% confidence interval, 1.69–6.35) compared with women of the same age without VTE. The corresponding hazard ratio in men aged <65 years was 2.06 (95% confidence interval, 1.32–3.20). Only 0.9% of the arterial events were attributed to VTE, and the VTE explained 63.8% of the risk of arterial events among VTE patients.

Conclusions—

Our findings imply that women and young men with VTE have higher risk of arterial thrombotic disease than those without VTE. However, only 1% of the arterial thrombotic events in the population are attributed to VTE.

Cardiovascular involvement in patients with pseudoexfoliation syndrome

AIM

Pseudoexfoliation (PEX) syndrome, diagnosed by ocular examination, is a common disorder of the extracellular matrix. Previous studies have demonstrated accumulation of PEX material in the walls of blood vessels and myocardium. We aimed to investigate whether PEX is associated with cardiovascular involvement using carotid ultrasound measurements and myocardial tissue Doppler imaging (TDI).

METHODS

Thirty-six PEX patients and 34 age-matched and sex-matched healthy controls who had no PEX material were included. Fasting blood samples were taken and the following data were obtained from all cases: myocardial TDI measurements, the mean carotid intima-media thickness (IMT), total carotid plaque area and number.

RESULTS

There were no significant differences between the groups regarding clinical and biochemical data. The peak systolic TDI velocities at the septal (septal S) and lateral annuli (lateral S), and the isovolumic contraction velocity at the lateral annulus [lateral isovolumic contraction velocity (IVC)] were significantly lower in patients with PEX, than in controls (P = 0.001, <0.001 and 0.016, respectively) whereas IMT, total carotid plaque area and number were significantly higher (P = 0.002, 0.035 and 0.033, respectively). In a logistic regression analysis including age, septal S, lateral S, lateral IVC, IMT, total carotid plaque area and number, septal S, lateral S and IMT were significantly associated with PEX, (P = 0.035, 0.011 and 0.035, respectively).

CONCLUSION

Peak systolic TDI velocities were significantly lower and IMT was significantly increased in patients with PEX. However, PEX was weakly associated with carotid plaque measurements.

Flow-mediated vasodilation was found to be an independent predictor of changes in the carotid plaque status during a 5-year follow-up

AIM

It has previously been shown that flow-mediated vasodilation is a predictor of the progression of the intima-media thickness (IMT). In the present study, the degree of endothelium-dependent vasodilation in both resistance and conduit arteries was evaluated as a predictor of the IMT and plaque progression.

METHODS

In the population-based Prospective Study of the Vasculature in Uppsala Seniors(PIVUS) trial(1,016 subjects all 70 years of age), the invasive forearm technique using acetylcholine administered in the brachial artery (resistance artery, EDV) and the brachial artery ultrasound technique with measurement of flow-mediated dilatation (conduit artery, FMD) were evaluated. The IMT and number of carotid arteries with plaques (0, 1 or 2) were recorded using ultrasound at the baseline investigation and the follow-up visit conducted five years later.

RESULTS

A total of 760 subjects had valid measurements of the IMT and carotid artery plaques at both the investigations conducted at 70 and 75 years of age. Neither the FMD nor EDV significantly predicted the change in IMT over five years. However, the FMD, but not EDV, was associated with the change in carotid plaque burden during the follow-up period, independent of classical risk factors, such as gender, waist circumference, fasting blood glucose, systolic and diastolic blood pressure, HDL- and LDL-cholesterol, serum triglycerides, BMI and smoking (OR 0.81 for a 1 SD change in FMD, 95%CI 0.68 to 0.95, p=0.010).

CONCLUSIONS

The FMD was found to be a predictor of changes in the carotid plaque status, but not IMT, during the 5-year follow-up period, independent of classical cardiovascular risk factors.

Comparacoes preliminares entre a histologia virtual ultrassonografica in vivo e os achados histopatologicos da placa carotidea produto de endarterectomia

CONTEXTO: A doença aterosclerótica da carótida extracraniana é uma das principais causas evitáveis de acidente vascular cerebral isquêmico (AVCi), sendo este a segunda causa mais comum de morte nos países desenvolvidos. Nos grandes estudos sobre a cirurgia carotídea, a indicação estava embasada fundamentalmente no grau de estenose arterial. Analisar somente o grau de estenose, entretanto, não revela todas as características da placa, na medida em que a morfologia e a composição da placa complementam a avaliação da doença carotídea avançada e são fundamentais para a análise e o acompanhamento da maioria das placas carotídeas tratadas clinicamente. OBJETIVO: Correlacionar a caracterização dos componentes da placa de ateroma pela histologia virtual ultrassonográfica (HVUS) com a histologia. MÉTODOS: As imagens pré-operatórias obtidas por ultrassonografia transcutânea de 12 placas de ateroma de bifurcação carotídea foram submetidas a um programa de computador, o qual correlacionou os níveis de cinza com os prováveis componentes da placa da bifurcação carotídea (HVUS). Estes achados foram correlacionados com o exame anatomopatológico das placas coletadas pela cirurgia de endarterectomia. RESULTADOS: O coeficiente de correlação de Pearson para os conteúdos de lipídeos e músculo/tecido fibroso foram, respectivamente, R=0,83 para gordura e R=0,91 para músculo/tecido fibroso. Quanto ao cálcio e ao sangue, foram R=0,05 e R=0,19, respectivamente. CONCLUSÕES: O presente trabalho corrobora a literatura demonstrando que a histologia virtual computadorizada baseada em ultrassonografia transcutânea apresenta boa correlação com os achados da histologia quanto ao conteúdo da placa. Maiores estudos para a padronização da técnica e o aperfeiçoamento do programa de análise permitirão maior uso clínico deste método.

Progression of carotid intima-media thickness as predictor of vascular events: results from the IMPROVE study

OBJECTIVE

To investigate whether several different measures of carotid intima-media thickness (IMT) progression are associated with subsequent vascular events and whether such associations are independent of baseline carotid atherosclerotic profile and Framingham risk factors.

APPROACH AND RESULTS

A longitudinal cohort study (the Carotid Intima Media Thickness [IMT] and IMT-Progression as Predictors of Vascular Events in a High Risk European Population study) was performed in 7 centers in 5 European countries (Finland, France, Italy, the Netherlands, and Sweden). Three thousand four hundred eighty-two subjects (median age 64.1 years; 47.8% men) with ≥ 3 vascular risk factors were recruited and monitored for a postprogression median follow-up of 21.5 months, during which time 129 subjects experienced a first vascular event (incidence of 20.4 per 1000 person-years). The 15th month progression of mean and maximum carotid IMT of the left and right common carotids, bifurcations, internal carotid arteries, and their composite measures, as well as the fastest IMTmax progression (Fastest-IMT(max-progr)) detected in the whole carotid tree regardless of location, were used in statistical analyses. All carotid IMT measures showed significant progression during the first 15 months (P<0.001), but only the Fastest-IMT(max-progr) was significantly associated with the risk of subsequent vascular events. The Fastest-IMT(max-progr) association persisted after Bonferroni correction for multiple comparisons and after adjustments for Framingham risk factors and pharmacological treatments (all P<0.005). The use of Framingham Risk Score in place of Framingham risk factors provided almost identical results (P=0.003).

CONCLUSIONS

The Fastest-IMT(max-progr), a novel approach to assess carotid IMT progression, identifies focal increases of carotid IMT and, in contrast to other progression variables, is associated with cardiovascular risk.

Measurement of subclinical carotid atherosclerosis may help in predicting risk for stroke in patients with diabetes

Diabetes is one of the most important risk factor for stroke and cardiovascular disease (CVD), especially in young patients. The control of classical vascular risk factors failed in terms of prevention of stroke in patients with diabetes. In addiction, in these patients the glycemic control showed a benefit on microvascular disease but lacked an established benefit in macrovascular disease. Therefore, implementations of effective stroke prevention strategies appear necessary in patients with diabetes. Ultrasound surrogate or intermediate markers of carotid atherosclerosis include carotid intima-media thickness (cIMT), carotid plaque (CP), and carotid stiffness (STIFF) have been demonstrated to increase in patients with diabetes and to be able to predict risk for stroke. In this editorial we discuss the opportunity to prevent the onset of vascular disease in their "preclinical or subclinical" stage in patients with higher risk for stroke such as diabetic patients.

Multiple imputation for handling systematically missing confounders in meta-analysis of individual participant data

A variable is 'systematically missing' if it is missing for all individuals within particular studies in an individual participant data meta-analysis. When a systematically missing variable is a potential confounder in observational epidemiology, standard methods either fail to adjust the exposure-disease association for the potential confounder or exclude studies where it is missing. We propose a new approach to adjust for systematically missing confounders based on multiple imputation by chained equations. Systematically missing data are imputed via multilevel regression models that allow for heterogeneity between studies. A simulation study compares various choices of imputation model. An illustration is given using data from eight studies estimating the association between carotid intima media thickness and subsequent risk of cardiovascular events. Results are compared with standard methods and also with an extension of a published method that exploits the relationship between fully adjusted and partially adjusted estimated effects through a multivariate random effects meta-analysis model. We conclude that multiple imputation provides a practicable approach that can handle arbitrary patterns of systematic missingness. Bias is reduced by including sufficient between-study random effects in the imputation model.

Progression of carotid plaque volume predicts cardiovascular events

BACKGROUND AND PURPOSE

Carotid ultrasound evaluation of intima-media thickness (IMT) and plaque burden has been used for risk stratification and for evaluation of antiatherosclerotic therapies. Increasing evidence indicates that measuring plaque burden is superior to measuring IMT for both purposes. We compared progression/regression of IMT, total plaque area (TPA), and total plaque volume (TPV) as predictors of cardiovascular outcomes.

METHODS

IMT, TPA, and TPV were measured at baseline in 349 patients attending vascular prevention clinics; they had TPA of 40 to 600 mm(2) at baseline to qualify for enrollment. Participants were followed up for ≤5 years (median, 3.17 years) to ascertain vascular death, myocardial infarction, stroke, and transient ischemic attacks. Follow-up measurements 1 year later were available in 323 cases for IMT and TPA, and in 306 for TPV.

RESULTS

Progression of TPV predicted stroke, death or TIA (Kaplan-Meier logrank P=0.001), stroke/death/MI (P=0.008) and Stroke/Death/TIA/Myocardial infarction (any Cardiovascular event) (P=0.001). Progression of TPA weakly predicted Stroke/Death/TIA (P=0.097) but not stroke/death/MI (P=0.59) or any CV event (P=0.143); likewise change in IMT did not predict Stroke/Death/MI (P=0.13) or any CV event (P=0.455 ). In Cox regression, TPV progression remained a significant predictor of events after adjustment for coronary risk factors (P=0.001) but change in TPA did not. IMT change predicted events in an inverse manner; regression of IMT predicted events (P=0.004).

CONCLUSIONS

For assessment of response to antiatherosclerotic therapy, measurement of TPV is superior to both IMT and TPA.

Traditional risk factors are not major contributors to the variance in carotid intima-media thickness

BACKGROUND AND PURPOSE

Carotid intima-media thickness (cIMT) was a widely accepted ultrasound marker of subclinical atherosclerosis in the past. Although traditional risk factors may explain ≈50% of the variance in plaque burden, they may not explain such a high proportion of the variance in IMT, especially when measured in plaque-freel ocations. We aimed this study to identify individuals with cIMT unexplained by traditional risk factors for future environmental and genetic research.

METHODS

As part of the Northern Manhattan Study, 1790 stroke-free individuals (mean age, 69±9 years; 60% women; 61% Hispanic; 19% black; 18% white) were assessed for cIMT using B-mode carotid ultrasound. Multiple linear regression models were evaluated: (1) incorporating prespecified traditional risk factors; and (2) including less traditional factors, such as inflammation biomarkers, adiponectin, homocysteine, and kidney function. Standardized cIMT residual scores were constructed to select individuals with unexplained cIMT.

RESULTS

Mean total cIMT was 0.92±0.09 mm. The traditional model explained 11% of the variance in cIMT. Age (7%), male sex (3%), glucose (<1%), pack-years of smoking (<1%), and low-density lipoprotein cholesterol (<1%) were significant contributing factors. The model, including inflammatory biomarkers, explained 16% of the variance in cIMT. Adiponectin was the only additional significant contributor to the variance in cIMT. We identified 358 individuals (20%) with cIMT unexplained by the investigated risk factors.

CONCLUSIONS

Vascular risk factors explain only a small proportion of variance in cIMT. Identification of novel genetic and environmental factors underlying unexplained subclinical atherosclerosis is of utmost importance for future effective prevention of vascular disease.

The sixth survey of the Tromso Study (Tromso 6) in 2007-08: collaborative research in the interface between clinical medicine and epidemiology: study objectives, design, data collection procedures, and attendance in a multipurpose population-based health survey

AIMS

To provide a synopsis of the sixth survey of the Tromsø Study, Tromsø 6, objectives and new target areas, study design, follow-up studies, data collection, attendance, and participant characteristics.

METHODS

The Tromsø Study, initiated in 1974, is an epidemiological, prospective study of health conditions and chronic diseases, and a resource for the surveillance of disease risk factors. The purpose of Tromsø 6 (2007-08) was to collect novel and repeated measurements of exposure data and to assess levels of disease risk factors. Tromsø 6 included a main study that comprised two screening visits and several follow-up studies. Main study data collection: First visit (n=12,984): questionnaires, interviews, measurements of height, weight, hip and waist circumference, heart rate, blood pressure, forearm bone density, grip strength, pain sensitivity measurements, and blood and hair samples and nose and throat swab cultures. Second visit (n=7307): sampling of biological specimens (blood, urine, nose and throat swab cultures) and clinical examinations (12-lead electrocardiography, cognitive tests, visual acuity test, retinal photography, carotid ultrasound, spirometry, dual-energy X-ray absorptiometry, and echocardiography.

RESULTS

A total of 12,984 participants aged 30-87 years were examined. The attendance rate was 66%, lower than in previous Tromsø Study surveys. The attendance was lowest in the youngest and oldest, those invited for the first time, and lower in men than women.

CONCLUSIONS

The completion of the survey with this comprehensive data collection went satisfactorily. The decreasing attendance rate calls for new recruitment strategies and optimisation of the study organisation to facilitate attendance.

Carotid intima-media thickness for cardiovascular risk assessment: systematic review and meta-analysis

OBJECTIVE

B-mode ultrasound measurement of the carotid intima-media thickness (CIMT) is a widely used marker for atherosclerosis and is associated with future cardiovascular events. This article provides a review and meta-analysis of the published evidence on the association of CIMT with future cardiovascular events and its additional value to traditional cardiovascular risk prediction models.

METHODS

A systematic review and meta-analysis of the evidence on the association of CIMT with future cardiovascular events and the additional value of CIMT to traditional cardiovascular risk prediction models was conducted. The association of CIMT with future cardiovascular events and the additional value of CIMT were calculated using random effects analysis.

RESULTS

The literature search yielded 1196 articles of which 15 articles provided sufficient data for the meta-analysis. A 1 SD increase in CIMT was predictive for myocardial infarction (HR 1.26, 95% CI 1.20-1.31) and for stroke (HR 1.31, 95% CI 1.26-1.36). A 0.1 mm increase in CIMT was predictive for myocardial infarction (HR 1.15, 95% CI 1.12-1.18) and for stroke (HR 1.17, 95% CI 1.15-1.21). The overall performance of risk prediction models did not significantly increase after addition of CIMT data. The areas under the curve increased from 0.726 to 0.729 (p = 0.8).

CONCLUSIONS

CIMT as measured by B-mode ultrasound is associated with future cardiovascular events. However, the addition of CIMT to traditional cardiovascular risk prediction models does not lead to a statistical significantly increase in performance of those models.

Association between presence of the metabolic syndrome and its components with carotid intima-media thickness and carotid and femoral plaque area: a population study

BACKGROUND

We aimed to explore the association between presence and number of components of the Metabolic Syndrome (MetS) and subclinical atherosclerosis outcomes (common carotid intima media thickness, plaque presence and sum of plaque area) in both the carotid and femoral bifurcations.

METHODS

Cross-sectional analysis of 771 volunteers from the ongoing epidemiological Cyprus Study (46% male; mean age = 60.1 ± 9.8). (a) Carotid intima-media thickness (IMTcc), (b) sum of plaque area in the carotid bifurcations (sum of the largest plaques in each carotid bifurcation-SPAcar), (c) sum of plaque area in the femoral bifurcations (sum of the largest plaques in each femoral bifurcation-SPAfem) and (d) sum of plaque area in both carotid and femoral bifurcations (sum of the areas of the largest plaques present in each of the four bifurcations-SPA) were measured at baseline using ultrasound. Presence and number of components of the MetS was ascertained using the National Cholesterol Education Program ATPIII definition and their association tested using multivariable regression models.

RESULTS

MetS was present in 259 (33.6%) individuals and was associated with a 0.02 mm increase in IMTcc (95% CI: 0.00 to 0.04, p = 0.047) after adjustment for age, sex, family history of CVD, alcohol consumption (BU/week) and smoking (pack-years). Each additional component of the MetS was associated with a 16% higher SPA (95% CI: 6.8% to 25.2%, pfor trend = 0.001), a 10% higher SPAcar (95% CI: 5% to 24%, pfor trend = 0.003) and a 14% higher SPAfem in the adjusted model.

CONCLUSIONS

We confirm an association between the MetS and IMTcc as well as report for the first time an association between the MetS and its components and femoral plaque area, in a general population over 40 years of age. Having any risk factors for the MetS increases the risk for subclinical atherosclerosis, with the risk increasing with each additional component. Using the dichotomous definition of the MetS may be overlooking the risk for subclinical atherosclerosis -and by inference future cardiovascular events- associated with having less than 3 risk factors.

Evaluation of serum 25-hydroxyvitamin d as a predictor of carotid intima-media thickness and carotid total plaque area in nonsmokers: the tromsø study

Objective. Altered calcium homeostasis has been linked to increased intima-media thickness (IMT) and plaques. We aimed to investigate whether serum 25-hydroxyvitamin D (25(OH)D) and serum calcium are associated with IMT and plaques in nonsmoking population. Methods. Ultrasound of the right carotid artery with the measurements of IMT and plaques was performed in 4194 nonsmoking subjects with available measurements of serum 25(OH)D and total calcium. Linear regression was applied to study the linear relationships between variables. Multinomial logistic regression was used to evaluate predictors of increased IMT and total plaque area (TPA), adjusted for age, body mass index, systolic blood pressure, and total cholesterol. Results. There was no significant linear relationship between mean IMT, TPA, and either serum 25(OH)D or total serum calcium. One SD increase in serum 25(OH)D was independently associated with increased odds of being in the highest quartile of IMT in men (OR 1.30, 95% CI 1.12, 1.51). In women, 1 SD increase in serum 25(OH)D was independently associated with increased risk of being in the upper tertile of TPA (OR 1.15, 95% CI 1.01, 1.33). Conclusions. Impaired calcium homeostasis has no consistent association with mean IMT and TPA; however, increased serum 25(OH)D may predict subclinical atherosclerosis in nonsmokers.

Joint associations of 61 genetic variants in the nicotinic acetylcholine receptor genes with subclinical atherosclerosis in American Indians: a gene-family analysis

BACKGROUND

Atherosclerosis is the underlying cause of cardiovascular disease, the leading cause of morbidity and mortality in all American populations, including American Indians. Genetic factors play an important role in the pathogenesis of atherosclerosis. Although a single-nucleotide polymorphism (SNP) may explain only a small portion of variability in disease, the joint effect of multiple variants in a pathway on disease susceptibility could be large.

METHODS AND RESULTS

Using a gene-family analysis, we investigated the joint associations of 61 tag SNPs in 7 nicotinic acetylcholine receptor genes with subclinical atherosclerosis, as measured by carotid intima-media thickness and plaque score, in 3665 American Indians from 94 families recruited by the Strong Heart Family Study (SHFS). Although multiple SNPs showed marginal association with intima-media thickness and plaque score individually, only a few survived adjustments for multiple testing. However, simultaneously modeling of the joint effect of all 61 SNPs in 7 nicotinic acetylcholine receptor genes revealed significant association of the nicotinic acetylcholine receptor gene family with both intima-media thickness and plaque score independent of known coronary risk factors.

CONCLUSIONS

Genetic variants in the nicotinic acetylcholine receptor gene family jointly contribute to subclinical atherosclerosis in American Indians who participated in the SHFS. These variants may influence the susceptibility of atherosclerosis through pathways other than cigarette smoking per se.

Cadmium exposure is accompanied by increased prevalence and future growth of atherosclerotic plaques in 64-year-old women

OBJECTIVES

There is currently widespread exposure to the toxic metal cadmium through the diet as well as through smoking, and it has been suggested that cadmium exposure may increase the risk of cardiovascular disease. Here we examined whether cadmium exposure is associated with prevalence and growth of atherosclerotic plaques in the carotid arteries.

DESIGN AND SUBJECTS

The analyses were performed in a screening-based cohort of 64-year-old Caucasian women with stratified, random selection to groups with normal glucose tolerance, impaired glucose tolerance and diabetes (n = 599). We measured cadmium concentrations in blood and urine at baseline. In addition, we performed ultrasound examination to determine the prevalence and area of atherosclerotic plaques in the carotid arteries and assessed smoking history and other cardiovascular risk factors at baseline and at a follow-up examination after a mean of 5.4 years.

RESULTS

At baseline, blood cadmium levels were associated with increased risk of plaque and a large plaque area after adjustment for confounders. In women who had never smoked, blood cadmium levels correlated positively with plaque area at baseline. The occurrence of large plaques and the change in plaque area at follow-up were associated with blood and creatinine-corrected urinary cadmium concentrations at baseline after adjustment for confounders. Blood and urine cadmium levels added information to established cardiovascular risk factors in predicting progress of atherosclerosis.

CONCLUSIONS

We have shown that cadmium levels in blood and urine are independent factors associated with the development of atherosclerotic plaques at baseline as well as prospectively. This novel observation emphasizes the need to consider cadmium as a pro-atherogenic pollutant.

Use of carotid intima-media thickness regression to guide therapy and management of cardiac risks

OPINION STATEMENT

Although carotid intima-media thickness (IMT) has been broadly used as a tool to evaluate cardiovascular risk, its role as a surrogate endpoint is still debated. The main issue is the fact that no study has ever been powered to show a relationship between changes in carotid IMT during follow-up and cardiovascular events. A meta-analysis of existing clinical studies was performed to investigate this relationship but it failed to demonstrate a predictive role of regression in carotid IMT for cardiovascular events. The reasons for the lack of a clear evidence for a predictive role of IMT progression are unknown but are likely multifactorial. Firstly, it may depend on the fact that this index is not a pure atherosclerosis index. Second, carotid atherosclerosis does not always reflect coronary atherosclerosis. Furthermore, methodologic problems related to intra- and interobserver variability make this index not adequately reproducible when tracking the progression of carotid atherosclerosis. A further meta-analysis based on individual patient data, instead of published data, has been planned to better address the predictive role of IMT. Lastly, in the future, the variability of ultrasound measurements of carotid IMT are likely to be reduced by further development of automatic calculation of this index by magnetic resonance imaging.

Relevance of increased serum cystatin C to vascular alterations in obese children

OBJECTIVE

Epidemiological studies report a positive relationship between serum cystatin C and cardiovascular outcomes in adults. Here, we tested the relevance of cystatin C as a biomarker for early vascular alterations in severely obese children.

METHODS

Two hundred nineteen obese (140 girls; age = 11.7 ± 2.7 years, BMI Z-score = 4.7 ± 1.2 SD) and 262 non-obese children (129 girls; age = 11.6 ± 0.6 years, body mass index [BMI] Z-score = 0.1 ± 1.0 SD). Serum cystatin C was measured by immunonephelometry. Intima media thickness (IMT), incremental elastic modulus, and flow-mediated and glyceryl-trinitrate-mediated dilations were determined at the common carotid artery and the brachial artery in obese children.

RESULTS

Obese children had significantly higher serum cystatin C than normal weight controls (0.86 ± 0.01 vs. 0.80 ± 0.01, P < 0.0001). In obese children, serum cystatin C correlates positively with BMI and the homeostasis model assessment index and negatively with the quantitative insulin sensitivity check index and adiponectin. A positive relationship was found between serum cystatin C and carotid IMT (r = 0.23, P = 0.0005), which remained significant in multivariate models adjusted for BMI (P = 0.01) and adiponectin with a trend towards significance (P = 0.05).

CONCLUSION

This study positions cystatin C and adiponectin as covariables associated with arterial wall thickness in obese children. Although the underlying pathophysiology linking cystatin C to early vascular disease remains to be deciphered, cystatin C may represent a novel adipose tissue-derived biomarker implicated in obesity-related comorbidities early in life.

Psoriasis is associated with increased intima-media thickness--the Study of Health in Pomerania (SHIP)

BACKGROUND

Psoriasis has been associated with cardiovascular diseases, but its relationship to markers of subclinical atherosclerosis has not been fully elucidated. The aim of the study is to analyze the association of psoriasis with common carotid artery intima-media thickness (CCA-IMT) and plaque prevalence of the carotid arteries.

METHODS

Data of 1987 men and women aged 25-88 years from the population-based Study of Health in Pomerania (SHIP) in north-eastern Germany were used. Cross-sectional associations of psoriasis with IMT and carotid plaque prevalence were analyzed using linear and logistic regression models adjusted for relevant confounders (age, sex, smoking, alcohol consumption, waist circumference, physical activity, systolic blood pressure, anti-hypertensive medication, acetylsalicylic acid, HbA(1c), total/HDL cholesterol ratio, lipid-lowering medication).

RESULTS

Psoriasis was associated with mean CCA-IMT, but not with carotid plaque prevalence. Comparisons between subjects with and without psoriasis showed an adjusted mean difference of the CCA-IMT of 0.016 mm (95% confidence interval [CI]: 0.004 mm-0.028 mm, p < 0.01) and an odds ratio for plaque prevalence of 1.12 (95% CI: 0.85-1.47) after adjusting for confounders.

CONCLUSION

Our findings suggest that psoriasis is associated with increased carotid mean IMT and might therefore contribute to the atherosclerotic process and subsequent cardiovascular events.

Sonographic characteristics of carotid artery plaques: Implications for follow-up planning?

The aim of our study was to analyze the ultrasound characteristics of carotid plaques in an outpatient population and to determine their implications for planning the ultrasound follow-up.

MATERIALS AND METHODS

We studied 747 consecutive outpatients (397 [53%] of whom were women) who underwent color Doppler sonography of the carotid arteries. Most of the patients presented multiple cardiovascular risk factors or were being followed-up for carotid artery stenosis.

RESULTS

Stenosis ranging from 1% to 69% was observed at the level of the right internal carotid arteries (ICA) in 419 (56.1%) of the 747 patients and in the left ICA in 408 of 747 (54.5%). One hundred twenty-four (29.5%) of the 419 RICA plaques and 77 (18.8%) of the 408 LICA plaques were classified as type 1 or type 2 according to the modified Gray-Weale classification.

CONCLUSIONS

Type 1 and type 2 plaques, which are referred to as "vulnerable plaques," were found in 160 (21.4%) of the 747 patients we examined. These patients should be subjected to closer ultrasound follow-up, even if they have only moderate carotid artery stenosis.

Intima-media thickness predicts stroke risk in the Heinz Nixdorf Recall study in association with vascular risk factors, age and gender

BACKGROUND AND PURPOSE

Individual risk stratification requires reliable information on preexisting vascular disease. The intima-media thickness of the common carotid artery (CIMT) is a non-invasively accessible marker of atherosclerosis, which can be used for risk evaluation.

METHODS

In a sample of 3669 initially stroke-free subjects aged 45-75 years belonging to the population-based Heinz Nixdorf Recall cohort, the predictive value of CIMT for incident stroke was evaluated over 85.3 ± 17.4 months in addition to established risk factors.

RESULTS

In a multivariable Cox regression analysis with traditional cardiovascular risk factors including age, gender, systolic blood pressure, LDL and HDL, diabetes, body mass index, smoking and CIMT, CIMT was a moderate stroke predictor (hazard ratio = 1.20 per 0.1 mm, 95% confidence interval = 1.01-1.44; p = 0.043), additional to e.g. age (1.46 per 5 years, 1.21-1.75; p < 0.001), systolic blood pressure (1.16 per 10 mm Hg, 1.04-1.30; p = 0.008) and current smoking (1.93, 1.12-3.31; p = 0.014). CIMT was associated with stroke risk in subjects above but not below 65 years. CIMT predicted stroke events in men, but not women. CIMT discriminated stroke incidence specifically in subjects belonging to the highest Framingham risk score tercile.

CONCLUSIONS

CIMT is a moderate independent stroke predictor, which discriminates stroke incidence in subjects at high vascular risk.

Traditional cardiovascular risk factors explain the minority of the variability in carotid plaque

BACKGROUND AND PURPOSE

Subclinical atherosclerotic plaque is an important marker of increased vascular risk. Identifying factors underlying the variability in burden of atherosclerotic carotid plaque unexplained by traditional vascular risk factors may help target novel preventive strategies.

METHODS

As a part of the carotid substudy of the Northern Manhattan Study (NOMAS), 1790 stroke-free individuals (mean age, 69±9; 60% women; 61% Hispanic, 19% black, 18% white) were assessed for total plaque area (TPA) burden using 2-dimensional carotid ultrasound imaging. Multiple linear regression models were constructed. Model 1 used prespecified traditional risk factors: age, sex, low-density lipoprotein cholesterol, diabetes mellitus, pack-years of smoking, blood pressure, and treatment for blood pressure; and Model 2, an addition of socioeconomic and less traditional risk factors. The contributions of the components of the Framingham heart risk score and the NOMAS Global Vascular Risk Score to the TPA were explored.

RESULTS

Prevalence of carotid plaque was 58%. Mean TPA was 13±19 mm2. Model 1 explained 19.5% of the variance in TPA burden (R2=0.195). Model 2 explained 21.9% of TPA burden. Similarly, the Framingham heart risk score explained 18.8% and NOMAS global vascular risk score 21.5% of the TPA variance.

CONCLUSIONS

The variation in preclinical carotid plaque burden is largely unexplained by traditional and less traditional vascular risk factors, suggesting that other unaccounted environmental and genetic factors play an important role in the determination of atherosclerotic plaque. Identification of these factors may lead to new approaches to prevent stroke and cardiovascular disease.

Carotid artery plaque progression and cognitive decline: the Tromsø Study 1994-2008

BACKGROUND

Carotid atherosclerosis is a risk factor for stroke and cognitive decline, but knowledge on how progression of carotid atherosclerosis affects cognitive function in stroke-free individuals is scarce.

METHODS

In the population-based Tromsø study, we calculated the change in ultrasound-assessed carotid plaque number and total plaque area from baseline (survey 4) to follow-up 7 years later (survey 5) in 4274 middle-aged stroke-free subjects. Cognitive function was assessed at follow-up by the verbal memory test, the digit-symbol coding test, and the tapping test and repeated after an additional 6 years in a subgroup of 2042 subjects (survey 6). Associations between the average of survey 4 and survey 5 plaque scores and the progression of plaque scores and cognitive test scores were assessed in regression analyses adjusted for baseline age, sex, education, depression, and cardiovascular risk factors.

RESULTS

Progression of total plaque area was associated with lower scores in the digit-symbol coding test (multivariable adjusted standardized β, -0.03; 95% CI, -0.05 to -0.00; P = 0.04) and the tapping test (β, -0.03; 95% CI, -0.06 to -0.00; P = 0.03). Similar results were seen for progression of plaque number. The average plaque scores were associated with lower scores in all cognitive tests (P-values ≤ 0.01). No association was found between plaque scores and cognitive decline.

CONCLUSIONS

The average plaque scores were associated with lower scores in all cognitive tests. Progression of plaque scores was associated with lower scores in the digit-symbol coding test and the tapping test, but not with the verbal memory test or with cognitive decline.

Can metabolic syndrome presence predict carotid intima-media thickness?

The aim of this investigation was to analyze metabolic syndrome (MS) impact on carotid intima-media thickness (cIMT). Prospective study of 300 patients with suspected coronary artery disease admitted for an elective coronary angiography were evaluated. Patients with previously known cardiac disease were excluded. In the population, 23.0% were diabetics and 40.5% had MS (but no diabetes). cIMT was not significantly different in patients with MS, but was significantly higher in diabetic patients compared with MS and control patients. Independent predictors of cIMT were age, male gender, insulin, and high-density lipoprotein (HDL) cholesterol (the last one with an inverse association). In patients without MS, only age and HDL cholesterol were associated. In patients with MS, independent predictors were age, male gender, and glucose, and abdominal obesity showed an inverse relationship. In patients with stable angina, MS is not an independent predictor of cIMT. Nonmodifiable variables (age and gender) are the most important determinants of cIMT, as well as blood glucose, in MS patients. Abdominal obesity was protective. J Clin Hypertens (Greenwich). 2012;00:00-00. ©2012 Wiley Periodicals, Inc.