Individual participant time-to-event data from multiple prospective epidemiologic studies enable detailed investigation into the predictive ability of risk models. Here we address the challenges in appropriately combining such information across studies. Methods are exemplified by analyses of log C-reactive protein and conventional risk factors for coronary heart disease in the Emerging Risk Factors Collaboration, a collation of individual data from multiple prospective studies with an average follow-up duration of 9.8 years (dates varied). We derive risk prediction models using Cox proportional hazards regression analysis stratified by study and obtain estimates of risk discrimination, Harrell's concordance index, and Royston's discrimination measure within each study; we then combine the estimates across studies using a weighted meta-analysis. Various weighting approaches are compared and lead us to recommend using the number of events in each study. We also discuss the calculation of measures of reclassification for multiple studies. We further show that comparison of differences in predictive ability across subgroups should be based only on within-study information and that combining measures of risk discrimination from case-control studies and prospective studies is problematic. The concordance index and discrimination measure gave qualitatively similar results throughout. While the concordance index was very heterogeneous between studies, principally because of differing age ranges, the increments in the concordance index from adding log C-reactive protein to conventional risk factors were more homogeneous.
C index; coronary heart disease; D measure; individual participant data; inverse variance; meta-analysis; risk prediction; weighting
Background The extent to which adult height, a biomarker of the interplay of genetic endowment and early-life experiences, is related to risk of chronic diseases in adulthood is uncertain.
Methods We calculated hazard ratios (HRs) for height, assessed in increments of 6.5 cm, using individual–participant data on 174 374 deaths or major non-fatal vascular outcomes recorded among 1 085 949 people in 121 prospective studies.
Results For people born between 1900 and 1960, mean adult height increased 0.5–1 cm with each successive decade of birth. After adjustment for age, sex, smoking and year of birth, HRs per 6.5 cm greater height were 0.97 (95% confidence interval: 0.96–0.99) for death from any cause, 0.94 (0.93–0.96) for death from vascular causes, 1.04 (1.03–1.06) for death from cancer and 0.92 (0.90–0.94) for death from other causes. Height was negatively associated with death from coronary disease, stroke subtypes, heart failure, stomach and oral cancers, chronic obstructive pulmonary disease, mental disorders, liver disease and external causes. In contrast, height was positively associated with death from ruptured aortic aneurysm, pulmonary embolism, melanoma and cancers of the pancreas, endocrine and nervous systems, ovary, breast, prostate, colorectum, blood and lung. HRs per 6.5 cm greater height ranged from 1.26 (1.12–1.42) for risk of melanoma death to 0.84 (0.80–0.89) for risk of death from chronic obstructive pulmonary disease. HRs were not appreciably altered after further adjustment for adiposity, blood pressure, lipids, inflammation biomarkers, diabetes mellitus, alcohol consumption or socio-economic indicators.
Conclusion Adult height has directionally opposing relationships with risk of death from several different major causes of chronic diseases.
Height; cardiovascular disease; cancer; cause-specific mortality; epidemiological study; meta-analysis
How 9p21 variation affects risk of cardiovascular disease is unclear, so we assessed whether 9p21 variants are associated with arterial elasticity or retinal microvascular findings.
In the prospective Multi-Ethnic Study of Atherosclerosis (MESA) we assessed 378 SNPs in the 9p21 locus. Within four ethnic groups, we used an additive genetic model to relate the 9p21 SNPs to five vascular phenotypes: small and large elasticity derived from radial diastolic pulse contour analysis; Young’s elastic modulus from carotid artery ultrasound measurements; and the diameter of the central retinal arteries and veins.
In neither ethnic-specific nor pooled data was there any statistically significant association between any of the 9p21 SNPs and any of the five vascular phenotypes.
Our study does not support an association of 9p21 variation with arterial elasticity or retinal microvascular abnormalities.
Prospective study; 9p21 SNP; retinal microvascular abnormalities; arterial elasticity
The association of individual fatty acids with ischemic stroke has not been thoroughly studied, and results have been inconsistent. Few prospective studies have systematically explored the association of biomarkers of fatty acid intake with stroke. The aim of this study was to explore which individual plasma fatty acids would be associated with higher risk of ischemic stroke among whites.
We studied 3,870 white men and women from the Minneapolis field center of the Atherosclerosis Risk in Communities (ARIC) Study, aged 45–64 at baseline (1987–89) who had plasma cholesterol ester (CE) and phospholipid (PL) fatty acids measured. Participants were followed through 2008 for incident ischemic stroke. Hazard ratios (HRs) with 95% confidence intervals (CIs) across quartiles of each fatty acid, measured as the percentage of total fatty acids, were calculated using Cox proportional hazards model.
During a maximum of 22-years of follow-up, we identified 168 cases of ischemic stroke. After adjustment for age and sex, plasma levels of saturated fatty acids were associated positively: HR (95%CI) of the highest quartile vs the lowest quartile for CE fraction was 1.93 (1.23–3.04), p for trend =0.01 and that for PL fraction was 1.64 (1.05–2.57), p for trend =0.03. There was also a positive linear association with monounsaturated fatty acids, especially with palmitoleic acid: HR (95%CI) of the highest quartile vs the lowest quartile for CE fraction was 1.86 (1.20–2.87), p for trend =0.003 for CE; and those for PL fraction was 1.52 (0.99–2.34), p for trend =0.005. No associations of ω-3 and ω-6 polyunsaturated fatty acids with ischemic stroke were observed, but linoleic acid was inversely and nonlinearly associated with ischemic stroke: HR (95%CI) of the highest quartile vs the lowest quartile for CE fraction was 0.64 (0.43–0.97), p for trend =0.13 and that for PL fraction was 0.69 (0.45–1.05), p for trend =0.24. These associations were generally unchanged after adjustment for cardiovascular risk factors.
In this US cohort of whites, we found significant positive associations of plasma saturated and monounsaturated fatty acids, especially of palmitoleic acid, with ischemic stroke. We also found an inverse nonlinear association between linoleic acid and ischemic stroke.
longitudinal study; epidemiology; fat; biomarkers; risk factors
Plasma lipoprotein-associated phospholipase A2 (Lp-PLA2) is an inflammatory marker associated positively with atherothrombotic risk. Whether Lp-PLA2 is related to risk of venous thromboembolism (VTE) is incompletely studied.
We assessed Lp-PLA2 activity in 10,687 Atherosclerosis Risk in Communities (ARIC) Study participants and followed them a median of 8.3 years (from 1996–98 through 2005) for VTE occurrence (n = 226).
There was no significant association between baseline Lp-PLA2 quartiles and risk of VTE, neither overall nor stratified as provoked or unprovoked. Adjusted for other risk factors, the hazard ratios (95% confidence interval) of total VTE across quartiles of Lp-PLA2 were 1.0 (reference), 0.95 (0.64, 1.42), 1.03 (0.69, 1.56), and 1.26 (0.83, 1.91). In the subset of participants with LDL-cholesterol ≥ 130 mg/dL, hazard ratios of total VTE were 1.00, 1.39 (0.44, 4.44), 2.45 (0.84, 7.11), and 2.84 (0.99, 8.14).
Our study does not support the overall hypothesis that elevated Lp-PLA2 contributes to VTE occurrence in the general population. However, in the presence of high LDL-cholesterol there was some evidence that Lp-PLA2 may increase VTE risk.
lipoprotein-associated phospholipase A2; prospective study; pulmonary embolism; venous thromboembolism
Height is inversely associated with incident coronary disease and total stroke, but few studies have examined the association between height and intraparenchymal hemorrhage. We hypothesized height would be inversely associated with incident intraparenchymal hemorrhage in the combined cohorts of the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study.
Data on Caucasian and African American participants were used to estimate the association of height at baseline with incident intraparenchymal hemorrhage verified by MD review of medical records and imaging reports. Sex-specific Cox proportional hazards regression models were used to calculate hazard ratios.
A total of 20,983 participants initially free of stroke (11,788 women, 9,195 men) were followed for an average of 15.9 years (SD = 5.1 years). Incident intraparenchymal hemorrhage occurred in 115 women and 73 men. Sex, but not age, race, study or blood pressure, modified the association, p = 0.03. After adjustment for risk factors (age, systolic blood pressure, triglycerides, LDL-cholesterol, fibrinogen and race), among women, height was significantly inversely associated with incident intraparenchymal hemorrhage [hazard ratio per standard deviation (6.3 cm) = 0.81, 95% CI (0.66 – 0.99)], p = 0.04. The hazard ratio (95% CI) for tertile 3 versus 1 in women was 0.63 (0.37–1.08). Among men, height was not linearly associated with incident intraparenchymal hemorrhage [hazard ratio per standard deviation (6.7 cm) = 1.09, 95% CI (0.84 – 1.40)], p = 0.52.
This large prospective study provides evidence that shorter height may be a risk factor for incident intraparenchymal hemorrhage in women.
Background and Purpose
Increased levels of plasma troponins and natriuretic peptides are associated with increased risk of cardiovascular disease, but only limited information exists on these biomarkers and stroke occurrence. In a prospective epidemiological study, we tested the hypothesis that high-sensitivity troponin T (TnT) and N-terminal pro B-type natriuretic peptide (NT-proBNP) are associated positively with incidence of stroke.
The Atherosclerosis Risk in Communities (ARIC) Study measured plasma TnT and NT-proBNP in 10,902 men or women initially free of stroke and followed them for a mean of 11.3 years for stroke occurrence (n=507).
Both biomarkers were associated positively with total stroke, nonlacunar ischemic, and especially, cardioembolic stroke, but not with lacunar or hemorrhagic stroke. For example, after adjustment for prevalent risk factors and cardiac diseases, the hazard ratios (95% confidence intervals) for jointly high values of TnT and NT-proBNP (versus neither biomarker high) were 2.70 (1.92, 3.79) for total stroke and 6.26 (3.40, 11.5) for cardioembolic stroke. Associations with stroke appeared somewhat stronger for NT-proBNP than TnT. Strikingly, approximately 58% of cardioembolic strokes occurred in the highest quintile of pre-stroke NT-proBNP, and 32% of cardioembolic strokes occurred in participants who had both NT-proBNP in the highest quintile and were known by ARIC to have atrial fibrillation sometime before their cardioembolic stroke occurrence.
In the general population, elevated plasma TnT and NT-proBNP concentrations are associated with increased risk of cardioembolic and other nonlacunar ischemic strokes.
epidemiology; natriuretic peptides; risk factors; stroke; troponins
To evaluate the associations of high sensitivity Troponin T (Hs-TnT), N-terminal pro-brain natriuretic peptide (NT-proBNP), and high sensitivity C-reactive protein (Hs-CRP) with mortality from any cause, cardiovascular disease (CVD), coronary heart disease (CHD), stroke, cancer, and respiratory disease in the Atherosclerosis Risk in Communities (ARIC) cohort.
11193 participants aged 54-74 years, initially free of the conditions being studied, had biomarkers measured and were followed for a mean of 9.9 years.
Hazard ratios (HR), adjusted for multiple risk factors, for mortality in participants in the highest Hs-TnT category compared to those with undetectable levels were: total 3.42 (95% Confidence Interval: 2.75-4.26), CVD 7.34 (4.64-11.6), CHD 6.06 (2.91-12.6), stroke 3.31 (1.26-8.66), cancer 1.60 (1.08-2.38) and respiratory 3.85 (1.39-10.7). Comparing the highest NT-proBNP quintile to those in the lowest quintile, the adjusted HRs for mortality were: total 3.05 (2.46-3.77), CVD 7.48 (4.67-12.0), CHD 4.07 (2.07-7.98) and stroke 10.4 (2.26-47.7). Comparing extreme Hs-CRP quintiles, the adjusted HRs for mortality were: total 1.61 (1.32-1.97), CVD 1.76 (1.19-2.62) and respiratory 3.36 (1.34-8.45). Having multiple markers elevated simultaneously greatly increased cause-specific mortality risks.
Greater levels of Hs-TnT, NT-proBNP and Hs-CRP are associated with increased risk of death, not just from cardiovascular disease but also from some non-cardiovascular causes.
biomarkers; troponin T; B natriuretic peptide; C- reactive protein; mortality
Plasma fibrinogen is an acute phase protein playing an important role in the blood coagulation cascade having strong associations with smoking, alcohol consumption and body mass index (BMI). Genome-wide association studies (GWAS) have identified a variety of gene regions associated with elevated plasma fibrinogen concentrations. However, little is yet known about how associations between environmental factors and fibrinogen might be modified by genetic variation. Therefore, we conducted large-scale meta-analyses of genome-wide interaction studies to identify possible interactions of genetic variants and smoking status, alcohol consumption or BMI on fibrinogen concentration. The present study included 80,607 subjects of European ancestry from 22 studies. Genome-wide interaction analyses were performed separately in each study for about 2.6 million single nucleotide polymorphisms (SNPs) across the 22 autosomal chromosomes. For each SNP and risk factor, we performed a linear regression under an additive genetic model including an interaction term between SNP and risk factor. Interaction estimates were meta-analysed using a fixed-effects model. No genome-wide significant interaction with smoking status, alcohol consumption or BMI was observed in the meta-analyses. The most suggestive interaction was found for smoking and rs10519203, located in the LOC123688 region on chromosome 15, with a p value of 6.2×10−8. This large genome-wide interaction study including 80,607 participants found no strong evidence of interaction between genetic variants and smoking status, alcohol consumption or BMI on fibrinogen concentrations. Further studies are needed to yield deeper insight in the interplay between environmental factors and gene variants on the regulation of fibrinogen concentrations.
This study evaluated the prevalence of ideal cardiovascular (CV) health in the Atherosclerosis Risk in Communities Study and determined its relationship with prevalent retinopathy, wider retinal venular diameters, and narrower arteriolar diameters, which are risk markers for subclinical cerebrovascular disease and are associated with increased stroke and coronary heart disease (CHD) morbidity and mortality.
Methods and Results
We used gradings of fundus photography measurements from the Atherosclerosis Risk in Communities Study to examine the association of retinopathy and retinal arteriolar and venular calibers to the number of ideal CV health metrics. Prevalent retinopathy showed a graded relationship with the CV health categories and number of ideal CV health metrics present: retinopathy prevalence was 2.1% among those with ≥5 ideal CV health metrics compared with 13.1% among those with zero ideal CV health metrics (odds ratio [CI]), 4.8 [2.5 to 8.9]). Central retinal venule equivalent and central retinal arteriolar equivalent diameters also showed graded relationships with CV health categories and number of ideal CV health metrics: after adjustment for age, race, sex, and education, mean central retinal venular equivalent was 187.8 μm (95% CI, 186.9 to 188.6 μm) among those with ≥5 ideal CV health metrics compared with 201.1 μm (95% CI, 199.1 to 203.1 μm) among those with zero ideal CV health metrics. Mean central retinal arteriolar equivalent was 163.8 μm (95% CI, 163.0 to 164.5 μm) among those with ≥5 ideal CV health metrics compared with 157.9 μm (95% CI, 156.1 to 159.7 μm) among those with zero ideal CV health metrics.
Few adults had ideal cardiovascular health. Those with the best level of health were less likely to have retinopathy signs, wide retinal venules, and narrow retinal arterioles, which are associated with increased stroke and coronary heart disease risk.
cardiovascular diseases; cardiovascular health metrics; cerebrovascular circulation; epidemiology; risk factors
To assess whether markers of acculturation (birthplace, number of U.S. generations) and socioeconomic status (SES) are associated with carotid artery plaque, internal carotid intima-media thickness (IMT), and albuminuria, in four racial/ethnic groups.
Using Multi-Ethnic Study of Atherosclerosis data (n = 6,716; age: 45-84) and race-specific binomial regression models, we computed prevalence ratios, adjusted for demographics and traditional cardiovascular risk factors.
The adjusted U.S. to foreign-born prevalence ratio (99% CI) for carotid plaque was 1.20 (0.97, 1.39) in Whites, 1.91 (0.94, 2.94) in Chinese, 1.62 (1.28, 2.06) in Blacks, and 1.23 (1.15, 1.31) in Hispanics. Greater carotid plaque prevalence was also found among Whites, Blacks, and Hispanics with more generations of US residence (p<0.001). Lower educational attainment and/or income were associated with greater carotid plaque prevalence in Whites and Blacks. Similar associations were observed with IMT. There was also some evidence of an inverse association between albuminuria and SES, in Whites and Hispanics.
Greater U.S. acculturation and lower SES were associated with a higher prevalence of carotid plaque and IMT, while little association was found with albuminuria.
To determine whether the 9p21 SNP association with coronary heart disease is modified by other classical or novel risk markers.
The 9p21 SNP (rs10757274) and multiple risk markers were measured in the Atherosclerosis Risk in Communities Study, and incident coronary disease events were ascertained. Effect modification (interaction) of the 9p21 SNP with risk markers was tested in Cox proportional hazard regression models.
The incidence rates of coronary heart disease per 1000 person-years were 14.4, 17.0, and 18.7 for AA, AG, and GG genotypes, yielding hazard ratios of 1.0, 1.20 (95% CI = 1.07-1.36), and 1.34 (95% CI = 1.16-1.53). There was no meaningful evidence of an interaction (all p-interaction > 0.04) between 9p21 SNP and any of 14 other risk markers for coronary heart disease. These included novel markers not previously explored for 9p21 interaction (e.g., cardiac troponin T and N-terminal pro-brain natriuretic peptide).
Our study extends evidence that the 9p21 SNP association with coronary heart disease is not modified by classical or novel risk markers. Our findings therefore rule out additional plausible pathways by which 9p21 might have increased coronary heart disease risk.
coronary disease; prospective study; 9p21 SNP
Many studies, including the Atherosclerosis Risk in Communities (ARIC) cohort, reported a positive association between plasma C-reactive protein (CRP) – a biomarker of low-grade chronic inflammation – and colorectal cancer risk, although it is unclear if the association is causal. Our aims were to assess the associations of a CRP genetic risk score (CRP-GRS) created from single nucleotide polymorphisms (SNPs) with colorectal cancer risk, as well as examine plasma CRP and CRP-GRS in relation to common cancers in the ARIC cohort.
Cox proportional hazards models were used to prospectively estimate hazard ratios (HR) and (95% confidence interval, CI) of total, colorectal, lung, prostate, and breast cancers in relation to: 1) CRP-GRS among 8,657 Whites followed in 1987–2006 and 2) log-transformed plasma CRP among 7,603 Whites followed in 1996–2006. A weighted CRP-GRS was comprised of 20 CRP-related SNPs located in/near CRP, APOC1, HNF1A, LEPR and 16 other genes that were identified in genome-wide association studies.
After multivariable adjustment, one standard deviation increment of the CRP-GRS was associated with colorectal cancer risk (HR=1.19; 95% CI, 1.03–1.37) but not with any other cancer. One unit of log-transformed plasma CRP was associated with the risk of total, colorectal, lung, and breast cancers: HRs (95% CIs) were 1.08 (1.01–1.15), 1.24 (1.01–1.51), 1.29 (1.08–1.54), and 1.27 (1.07–1.51), respectively. HRs remained elevated, although lost statistical significance for all but breast cancer, after excluding subjects with <2 years of follow-up.
The study corroborates a causative role of chronic low-grade inflammation in colorectal carcinogenesis.
inflammation; CRP; cancer risk; genetic risk score; genetic polymorphism; ARIC cohort
Among the various cardiovascular diseases, heart failure (HF) is projected to have the largest increases in incidence over the coming decades; therefore, improving HF prediction is of significant value. We evaluated whether cardiac troponin T (cTnT) measured with a high-sensitivity assay and N-terminal-pro-B-type natriuretic peptide (NT-proBNP), biomarkers strongly associated with incident HF, improve HF risk prediction in the Atherosclerosis Risk In Communities (ARIC) study.
Using gender-specific models, cTnT and NT-proBNP were added to age and race (“laboratory report” model), and to the ARIC HF model (includes age, race, systolic blood pressure, antihypertensive-medication use, current/former smoking, diabetes, body mass index, prevalent coronary heart disease and heart rate) in 9868 subjects without prevalent HF; area under the receiver operating characteristic curve (AUC), integrated discrimination improvement, net reclassification improvement (NRI) and model fit were described.
Over a mean follow-up of 10.4 years, 970 subjects developed incident HF. Adding cTnT and NT-proBNP to the ARIC HF model significantly improved all statistical parameters (AUCs increased by 0.040 and 0.057; the continuous NRI was 50.7% and 54.7% in women and men, respectively). Interestingly, the simpler laboratory report model was statistically no different than the ARIC HF model.
cTnT and NT-proBNP have significant value in HF risk prediction. A simple gender-specific model that includes age, race, cTnT and NT-proBNP (which can be incorporated in a laboratory report) provides a good model, whereas adding cTnT and NT-proBNP to clinical characteristics results in an excellent HF prediction model.
cardiac troponin T; NT-proBNP; heart failure; ARIC; risk prediction
Although the incidence of and mortality following ST-segment elevation myocardial infarction (STEMI) is decreasing, time-trends in anatomical location of STEMI and associated short-term prognosis have not been examined in a population-based community study. We determined 22-year trends in age- and race-adjusted, gender-specific incidence rates and 28-day case fatality of hospitalized STEMI by anatomic infarct location among a stratified random sample of 35-74 year old residents of four communities in the Atherosclerosis Risk in Communities (ARIC) study. STEMI infarct location was assessed by 12-lead electrocardiograms (ECG) from the hospital record, and was coded as anterior, inferior, lateral and multi-location STEMI using the Minnesota Code. Between 1987 and 2008, a total of 4,845 patients had an incident STEMI; 37.2% were inferior STEMI; 32.8% were anterior; 16.8% occurred in multiple infarct locations and 13.2% were lateral STEMI. For inferior, anterior and lateral STEMI in both men and women, significant declines were observed in the age-adjusted annual incidence rate and the associated 28-day case fatality. In contrast, for STEMI in multiple infarct locations, neither the annual incidence rate nor the 28-day case fatality changed over time. The age- and race-adjusted annual incidence rate and associated 28-day case fatality of STEMI in anterior, inferior and lateral infarct locations declined over 22 years of surveillance; however, no decline was observed for STEMI in multiple infarct locations. In conclusion, our findings suggest there is room for improvement in the care of patients with multi-location STEMI.
ST segment elevation myocardial infarction; Epidemiology; Trends
Lp(a); venous thrombosis; pulmonary embolus; risk factors; prospective study; epidemiology
Cardiovascular risk prediction models based on classical risk factors identified in epidemiologic cohort studies are useful in primary prevention of cardiovascular disease in individuals. This article briefly reviews aspects of cardiovascular risk prediction in the United States and efforts to evaluate novel risk factors. Even though many novel risk markers have been found to be associated with cardiovascular disease, few appear to improve risk prediction beyond the powerful, classical risk factors. A recent US consensus panel concluded that clinical measurement of certain novel markers for risk prediction was reasonable, namely, hemoglobin A1c (in all adults), microalbuminuria (in patients with hypertension or diabetes), and C-reactive protein, lipoprotein-associated phospholipase, coronary calcium, carotid intima-media thickness, and ankle/brachial index (in patients deemed to be at intermediate cardiovascular risk, based on traditional risk factors).
risk factors; coronary disease; cardiovascular disease; epidemiology
To determine whether the burden of leukoaraiosis and the number of brain infarcts, defined by MRI, are prospectively and independently associated with intraparenchymal hemorrhage (IPH) incidence in a pooled population-based study.
Among 4,872 participants initially free of clinical stroke in the Atherosclerosis Risk in Communities (ARIC) Study and the Cardiovascular Health Study (CHS), we assessed white matter grade (range 0–9), reflecting increasing leukoaraiosis, and brain infarcts using MRI. Over a median of 13 years of follow-up, 71 incident, spontaneous IPH events occurred.
After adjustment for other IPH risk factors, the hazard ratios (95% confidence intervals) across white matter grades 0–1, 2, 3, and 4–9 were 1.00, 1.68 (0.86–3.30), 3.52 (1.80–6.89), and 3.96 (1.90–8.27) (p for trend <0.0001). These hazard ratios were weakened only modestly (p for trend = 0.0003) with adjustment for MRI-defined brain infarcts. The IPH hazard ratios for 0, 1, 2, or ≥3 MRI-defined brain infarcts were 1.00, 1.97 (1.10–3.54), 2.00 (0.83–4.78), and 3.12 (1.31–7.43) (p for trend = 0.002), but these were substantially attenuated when adjusted for white matter grade (p for trend = 0.049).
Greater MRI-defined burden of leukoaraiosis is a risk factor for spontaneous IPH. Spontaneous IPH should be added to the growing list of potential poor outcomes in people with leukoaraiosis.
Sick sinus syndrome (SSS) is a common indication for pacemaker implantation. Limited information exists on the association of sick sinus syndrome (SSS) with mortality and cardiovascular disease (CVD) in the general population.
We studied 19,893 men and women age 45 and older in the Atherosclerosis Risk in Communities (ARIC) study and the Cardiovascular Health Study (CHS), two community-based cohorts, who were without a pacemaker or atrial fibrillation (AF) at baseline. Incident SSS cases were validated by review of medical charts. Incident CVD and mortality were ascertained using standardized protocols. Multivariable Cox models were used to estimate the association of incident SSS with selected outcomes.
During a mean follow-up of 17 years, 213 incident SSS events were identified and validated (incidence, 0.6 events per 1,000 person-years). After adjustment for confounders, SSS incidence was associated with increased mortality (hazard ratio [HR] 1.39, 95% confidence interval [CI] 1.14–1.70), coronary heart disease (HR 1.72, 95%CI 1.11–2.66), heart failure (HR 2.87, 95%CI 2.17–3.80), stroke (HR 1.56, 95%CI 0.99–2.46), AF (HR 5.75, 95%CI 4.43–7.46), and pacemaker implantation (HR 53.7, 95%CI 42.9–67.2). After additional adjustment for other incident CVD during follow-up, SSS was no longer associated with increased mortality, coronary heart disease, or stroke, but remained associated with higher risk of heart failure (HR 2.00, 95%CI 1.51–2.66), AF (HR 4.25, 95%CI 3.28–5.51), and pacemaker implantation (HR 25.2, 95%CI 19.8–32.1).
Individuals who develop SSS are at increased risk of death and CVD. The mechanisms underlying these associations warrant further investigation.
Estimates of the heritability of plasma fibrinogen concentration, an established predictor of cardiovascular disease (CVD), range from 34 to 50%. Genetic variants so far identified by genome-wide association (GWA) studies only explain a small proportion (< 2%) of its variation.
Methods and Results
We conducted a meta-analysis of 28 GWA studies, including more than 90,000 subjects of European ancestry, the first GWA meta-analysis of fibrinogen levels in 7 African Americans studies totaling 8,289 samples, and a GWA study in Hispanic-Americans totaling 1,366 samples. Evaluation for association of SNPs with clinical outcomes included a total of 40,695 cases and 85,582 controls for coronary artery disease (CAD), 4,752 cases and 24,030 controls for stroke, and 3,208 cases and 46,167 controls for venous thromboembolism (VTE). Overall, we identified 24 genome-wide significant (P<5×10−8) independent signals in 23 loci, including 15 novel associations, together accounting for 3.7% of plasma fibrinogen variation. Gene-set enrichment analysis highlighted key roles in fibrinogen regulation for the three structural fibrinogen genes and pathways related to inflammation, adipocytokines and thyrotrophin-releasing hormone signaling. Whereas lead SNPs in a few loci were significantly associated with CAD, the combined effect of all 24 fibrinogen-associated lead SNPs was not significant for CAD, stroke or VTE.
We identify 23 robustly associated fibrinogen loci, 15 of which are new. Clinical outcome analysis of these loci does not support a causal relationship between circulating levels of fibrinogen and CAD, stroke or VTE.
Fibrinogen; cardiovascular disease; genome-wide association study
Background and Purpose
Carotid intima-media thickness (IMT) and electrocardiographic left ventricular hypertrophy (ECG-LVH) are two subclinical cardiovascular disease measures associated with increased risk of total and ischemic strokes. Increased IMT and ECG-LVH also may reflect end-organ hypertensive effects. Information is scant on the associations of these subclinical measures with intracerebral hemorrhage (ICH). We hypothesized that greater carotid IMT and the presence of ECG-LVH would be independently associated with increased ICH incidence.
Among 18,155 participants initially free of stroke in the Atherosclerosis Risk in Communities Study (ARIC) and the Cardiovascular Health Study (CHS), we assessed carotid IMT, carotid plaque, and ECG-LVH. Over a median of 18 years of follow-up, 162 incident ICH events occurred.
After adjustment for other ICH risk factors, carotid IMT was associated positively with incidence of ICH in both ARIC and CHS. The risk was lowest in study-specific quartile 1, elevated 1.6 to 2.6-fold in quartiles 2–3, and elevated 2.5 to 3.7-fold in quartile 4 (p<0.05 for both studies). In CHS, having a carotid plaque was associated with a 2-fold (95% CI = 1.1–3.4) greater ICH risk than having no plaque, but only 1.2-fold (95% CI = 0.76–2.0) greater ICH risk in ARIC. ECG-LVH carried a hazard ratio of ICH of 1.7 (95% CI = 0.77–3.7) in CHS and 2.8 (95% CI = 1.2–6.4) in ARIC.
Our data suggest that people with carotid atherosclerosis and possibly LVH are at increased risk not only of ischemic stroke but also of ICH.
atherosclerosis; left ventricular hypertrophy; intracerebral hemorrhage; prospective study; risk factors
To testthe hypothesis that inflammation measured by white blood cell count (WBC) and C-reactive protein (CRP) is associated positively with incident heart failure (HF).
Using the Atherosclerosis Risk in Communities (ARIC) Study, we conducted separate Cox proportional hazards regression analyses for WBC (measured 1987 to 1989) and CRP (measured 1996 to 1998) in relation to subsequent heart failure occurrence. A total of 14,485 and 9,978 individuals were included in the WBC and CRP analyses, respectively.
There were 1647 participants that developed HF during follow up after WBC assessment and 613 developed HF after CRP assessment. After adjustment for demographic variables and traditional HF risk factors, the hazard ratio (95% CI)for incident HF across quintiles of WBC was 1.0, 1.10 (0.9-1.34), 1.27(1.05-1.53), 1.44(1.19-1.74), and 1.62(1.34-1.96) (p trend <0.001); hazard ratio across quintiles of CRP was 1.0, 1.03 (0.68-1.55), 0.99 (0.66-1.51), 1.40 (0.94-2.09) and 1.70 (1.14-2.53) (p trend 0.002). Granulocytes appeared to drive the relation between WBCs and heart failure [hazard ratios across quintiles: 1.0, 0.93(0.76-1.15), 1.26 (1.04-1.53), 1.67(1.39-2.01) and 2.19 (1.83-2.61) (p trend <0.0001)], while lymphocytes or monocytes were not related.
Greater levels of WBC (especially granulocytes) and CRP are associated with increased risk of heart failure in middle-aged adults, independent of traditional risk factors.
Prospective Study; Risk Factors; Heart Failure; Inflammation; C-Reactive Protein; Leukocytes; Granulocytes
To estimate the prevalence of ideal cardiovascular health and its relation to incident cardiovascular disease (CVD).
An American Heart Association committee recently set a goal to improve the cardiovascular heath of Americans by 20% by 2020. The committee developed definitions of “ideal,” “intermediate,” or “poor” cardiovascular health for adults and children based on seven CVD risk factors or health behaviors.
We used data from the Atherosclerosis Risk in Communities (ARIC) Study cohort, aged 45–64 years, to estimate the prevalence of ideal cardiovascular health in 1987–89 and the corresponding incidence rates of CVD. Incident CVD comprised stroke, heart failure, myocardial infarction, or fatal coronary disease.
Among 12,744 participants initially free of CVD, only 0.1% had ideal cardiovascular health, 17.4% had intermediate cardiovascular health, and 82.5% had poor cardiovascular health. CVD incidence rates through 2007 showed a graded relation with the ideal, intermediate, and poor categories and with the number of ideal health metrics present: rates were one tenth as high in those with six ideal health metrics (3.9 per 1,000 person-years) compared with zero ideal health metrics (37.1 per 1,000 person-years).
In this community-based sample, few adults in 1987–9 had ideal cardiovascular health by the new AHA definition. Those who had the best levels of cardiovascular health nevertheless sustained relatively few events. Clearly, to achieve the AHA goal of improving cardiovascular health by 20% by 2020, we will need to redouble nationwide primordial prevention efforts at the population and individual levels.
epidemiology; risk factors; cardiovascular disease; stroke; coronary disease
Blacks are thought to have a higher risk of venous thromboembolism (VTE) than whites however prior studies are limited to administrative databases that lack specific information on VTE risk factors or have limited geographic scope.
Methods and Results
We ascertained VTE from three prospective studies; the Atherosclerosis Risk in Communities study (ARIC), the Cardiovascular Health Study (CHS), and the REasons for Geographic and Racial Differences in Stroke study (REGARDS). We tested the association of race with VTE using Cox proportional hazard models adjusted for VTE risk factors. Over 438,090 person-years, 916 incident VTE events (302 in blacks) occurred in 51,149 individuals (17,318 blacks) followed. In risk factor-adjusted models, blacks had a higher rate of VTE than whites in CHS (HR 1.81; 95% CI 1.20, 2.73) but not ARIC (HR 1.21; 95% CI 0.96, 1.54). In REGARDS, there was a significant region by race interaction (p = 0.01); blacks in the southeast had a significantly higher rate of VTE than blacks in the rest of the US (HR 1.63; 95% CI 1.08, 2.48) which was not seen in whites (HR 0.83; 95% CI 0.61, 1.14).
The association of race with VTE differed in each cohort, which may reflect the different time periods of the studies and/or different regional rates of VTE. Further study of environmental and genetic risk factors for VTE are needed to determine which underlie racial and perhaps regional differences in VTE.
Venous Thrombosis; Epidemiology; Race
Background and Purpose
Understanding associations of carotid atherosclerosis with stroke subtypes may contribute to more effective prevention of stroke.
Between 1987 and 1989, 13,560 men and women aged 45 to 64 years and free of clinical stroke, took part in the first examination of the Atherosclerosis Risk in Communities study. Incident strokes were ascertained by hospital surveillance.
During an average follow up of 15.7-years, 82 incident hemorrhagic and 621 incident ischemic strokes (131 lacunar, 358 nonlacunar, and 132 cardioembolic strokes) occurred. The incidence rates of hemorrhagic and ischemic strokes were greater across higher carotid intima-media thickness (IMT) levels. Although this positive association was observed for all stroke subtypes, the age-, sex-, and race-adjusted risk ratios (RR) were higher for cardioembolic and nonlacunar strokes than for hemorrhagic and lacunar strokes. Compared with participants in the lowest quintile (<0.61mm), the adjusted RRs for those in the highest quintile (≥0.85mm) of IMT were 2.55 (95%CI, 1.09 to 5.94) for hemorrhagic, 2.89 (95%CI, 1.50 to 5.54) for lacunar, 3.61 (95%CI, 2.33 to 5.99) for nonlacunar, and 6.12 (95%CI, 2.71 to 13.9) for cardioembolic stroke. The RRs were attenuated by additional adjustment for covariates, but remained statistically significant for nonlacunar and cardioembolic strokes (p for trend <0.001, respectively). The association between carotid IMT and lacunar stroke was somewhat stronger in African Americans than in whites (P for interaction = 0.07).
Carotid atherosclerosis was associated with increased risk of all stroke subtypes, but the association of carotid atherosclerosis with stroke may vary by subtypes.
Brain Infarction; Carotid artery; Epidemiology; Intima-media thickness; Stroke subtypes