Does the association of risk factors and atherosclerosis change with age? An analysis of the combined ARIC and CHS cohorts. The Atherosclerosis Risk in Communities (ARIC) and Cardiovascular Health Study (CHS) investigators

INTRODUCTION

A decrease in the estimated relative risk of cerebrovascular and cardiovascular diseases associated with known disease risk factors has been observed among elderly cohorts, perhaps suggesting that continued risk factor management in the elderly may not be as efficacious as with younger age groups. In this paper, the differential magnitude of the association of risk factors with atherosclerosis across the age spectrum from 45 years to older than 75 years is presented.

METHODS

Subclinical atherosclerosis as measured by carotid ultrasonography and risk factor prevalence were assessed using similar methods among participants aged 45 to 64 years in the Atherosclerosis Risk in Communities (ARIC) study and among participants 65 years and older in the Cardiovascular Health Study (CHS). Pooling these two cohorts provided data on the relationship of risk factors and atherosclerosis on nearly 19,000 participants over a broad age range. Regression analyses were used to assess the consistency of the magnitude of the association of risk factors with atherosclerosis across the age spectrum separately for black and white participants in cross-sectional analyses.

RESULTS

As expected, each of the risk factors was globally (across all ages) associated with increased atherosclerosis. However, the magnitude of the association did not differ across the age spectrum for hypertension, low density lipoprotein cholesterol (LDL-c), fibrinogen, or body mass index (BMI). For whites, there was a significantly greater impact of smoking and HDL-C among older age strata but a smaller impact of diabetes. For black women, the impact of HDL-C decreased among the older age strata.

CONCLUSIONS

These data suggest that most risk factors continue to be associated with increased atherosclerosis at older ages, possibly suggesting a continued value in investigation of strategies to reduce atherosclerosis by controlling risk factors at older ages.

Microalbuminuria and carotid artery intima-media thickness in nondiabetic and NIDDM subjects. The Insulin Resistance Atherosclerosis Study (IRAS)

BACKGROUND AND PURPOSE

Microalbuminuria is associated with cardiovascular mortality in subjects with non-insulin-dependent diabetes mellitus (NIDDM). However, little is known about this association in nondiabetic subjects. Specifically, it is not known whether microalbuminuria is related to an early stage of atherosclerosis manifested as increased intima-media thickness (IMT) of carotid arteries. We investigated the relationship between microalbuminuria and carotid artery IMT in 991 nondiabetic and 450 NIDDM subjects aged 40 to 69 years.

METHODS

Microalbuminuria was defined as albumin-to-creatinine ratio > or = 2 mg/mmol in a morning spot urine sample. B-mode ultrasound was used to assess the IMT of the common and internal carotid arteries.

RESULTS

Altogether 13.9% of nondiabetic and 27.6% of NIDDM subjects had microalbuminuria, and 31.1% of nondiabetic and 50.8% of NIDDM subjects had hypertension. Subjects with microalbuminuria had greater common carotid artery (CCA) IMT than those without microalbuminuria (nondiabetic: 0.84 +/- 0.02 versus 0.80 +/- 0.01 mm, P = .010; NIDDM: 0.89 +/- 0.02 versus 0.86 +/- 0.01 mm, P = .152; combined: 0.86 +/- 0.01 versus 0.82 +/- 0.01, P = .005). The association of microalbuminuria and CCA IMT was independent of age, sex, ethnicity, smoking, and lipoprotein levels. Although further adjustment for hypertension in the multivariate linear regression analysis attenuated the difference in CCA IMT between subjects with and without microalbuminuria, this difference continued to be significant (combined: 0.86 +/- 0.01 versus 0.83 +/- 0.01, P = .015). In contrast to CCA IMT, microalbuminuria was not related to ICA IMT.

CONCLUSIONS

Microalbuminuria was associated with increased CCA IMT. This relationship was only partly mediated by hypertension. Thus, microalbuminuria is related to atherosclerosis at an early stage of the disease process.

Concepts in orbital reconstruction

The diagnosis and management of orbital disease often requires the interaction of several specialties. The authors have reviewed the concepts in orbital reconstruction from an ophthalmologic, oculoplastic, otolaryngologic, and plastic surgical approach. Careful attention is given to the clinical examination, radiologic studies, surgical indications, and surgical techniques for orbital disease.

Preparation and evaluation of bacterial stocks for filter validation

Bacterial cell stock paste of Brevundimonas diminuta (American Type Culture Collection # 19146) used for filter validation was evaluated by standard microbiological procedures to determine culture purity, monodispersion, cell size, and strain identity. Tests performed included direct microscopic count, standard plate count, gram stain, streak plate, sizing by microfiltration, scanning electron microscopy, and biochemical identification. Results indicated the bacterial stocks were of consistent quality in terms of bacteriological purity, cell size, viability, and concentration. Sizing by microfiltration confirmed consistent monodispersion and cell retention characteristics for each lot tested. Use of the commercially available RapID NF Plus system confirmed each lot to be B. diminuta as indicated by biochemical profile and identification database. These tests represent parameters necessary for qualification of bacterial stocks to be used for filter validation.

Evaluation of social status as a contributing factor to the stroke belt region of the United States

BACKGROUND AND PURPOSE

The southeastern United States has stroke mortality rates above the national average. The causes for this excess mortality are unknown; however, lower socioeconomic status (SES) is a risk factor for stroke, and the lower SES in the Southeast is a potential cause. In this report we assess the proportion of the excess stroke mortality attributable to SES.

METHODS

The more than 400,000 participants in the National Longitudinal Mortality Study were categorized into three regions: the coastal plain region of North Carolina, South Carolina, and Georgia ("stroke buckle"); the remainder of these states plus five other southern states ("stroke belt"); and the remainder of the United States. The stroke mortality rates were calculated with and without adjustment for SES, and the proportion of the excess mortality attributable to SES was estimated.

RESULTS

In persons between the ages of 35 and 54 years, stroke mortality in the stroke buckle is estimated to be more than twice that of the rest of the nation and 1.7 times greater for ages 55 to 74 years. For persons in the stroke belt, the stroke mortality was 1.3 times greater than that in the rest of the nation for the ages of 35 to 54 and 55 to 74 years. Less than 16% of this excess stroke morality was attributable to SES.

CONCLUSIONS

SES does not appear to be a major contributor to the excess mortality in the southeastern United States. Of additional concern is the stroke buckle region, which was shown to have stroke mortality rates substantially greater than those in the traditionally recognized stroke belt.

Virus retention by a hydrophilic triple-layer PVDF microporous membrane filter

Retention of bacteriophages (phi 6, PR772, T1, and PP7) and mammalian viruses (poliovirus and influenza A virus) by a hydrophilic triple layer PVDF microporous membrane, the Ultipor VF grade DV50 membrane, was evaluated. Challenges of membrane discs or pleated filter cartridges were performed at concentrations of 10(6)-10(8) PFU/mL in one or more of the following carrier fluids: water, saline, gelatin (0.1%) in phosphate buffer, Dulbecco's Modified Eagle Medium (MEM), and MEM supplemented with 10% fetal bovine serum (MEM + 10). The data demonstrate a minimum log titer reduction (LTR) of 6 for viruses larger than 50 nm irrespective of the carrier fluid. Protein transmission levels of greater than 95% for IgG and albumin were achieved. For integral pleated filter cartridges, correlation between a nondestructive integrity test (using the forward flow integrity test method) and virus retention was demonstrated. The Ultipor VF grade DV50 filter can be applicable in the manufacture of biologicals and biopharmaceuticals, where high protein transmission and consistent viral titer reduction are desired.

Consistency of Doppler parameters in predicting arteriographically confirmed carotid stenosis. Asymptomatic Carotid Atherosclerosis Study Investigators

BACKGROUND AND PURPOSE

While internal carotid peak systolic velocity (IPSV) is reportedly the best Doppler parameter for predicting lower grades of carotid artery stenosis, the internal carotid end-diastolic velocity (IEDV) or the ratio of IPSV to common carotid end-diastolic velocity (CEDV) is helpful in increasing prediction of higher grade stenoses. It is important to examine the consistency of these findings across machine and technician.

METHODS

Using data from 10 devices from the Asymptomatic Carotid Atherosclerosis Study, we examined the predictive ability of seven Doppler parameters: IPSV, IEDV, CEDV, common carotid peak systolic velocity (CPSV), and the ratios of IPSV/ CEDV, IEDV/CEDV, and IEDV/CEDV. To assess the agreement between Doppler and arteriography in classifying percent stenosis above or below a given criterion, sensitivity, specificity, area under the receiver operating curve, and kappa statistics were obtained from logistic models. The single best Doppler parameter for each of two grades of stenosis (60% and 80%) was determined, and its predictive ability was compared with that of IPSV. The usefulness of IEDV or IPSV/CEDV in addition to IPSV to determine higher grade stenosis was examined.

RESULTS

IPSV was the best predictor in 9 of 10 devices at 60% and in 4 devices at 80% stenosis. When another parameter was better than IPSV, the improvement was minimal. Including IEDV or IPSV/CEDV in addition to IPSV did not notably improve predictive ability.

CONCLUSIONS

IPSV is the single best Doppler parameter for distinguishing severe (> 80%) from less severe carotid stenosis. Information from other Doppler parameters in addition to IPSV is unlikely to be helpful.

Insulin sensitivity and acute insulin response in African-Americans, non-Hispanic whites, and Hispanics with NIDDM: the Insulin Resistance Atherosclerosis Study

NIDDM is usually characterized by beta-cell failure and decreased insulin sensitivity. It has been reported that a high proportion of African-American NIDDM subjects are insulin sensitive. To examine this issue, we determined insulin sensitivity (S(I)) in 479 NIDDM subjects by minimal model analyses of frequently sampled intravenous glucose tolerance (FSIGT) from the Insulin Resistance Atherosclerosis Study (IRAS), a large multicenter study of insulin sensitivity and cardiovascular risk in African-Americans, Hispanics, and non-Hispanic whites. The African-Americans and non-Hispanic whites were sampled in Los Angeles and Oakland, California. The non-Hispanic whites and Hispanics were sampled in San Antonio, Texas, and San Luis Valley, Colorado. We defined the proportion of insulin-sensitive (S(I)) subjects as > or =1.61 min-1 x microU-1 x ml-1, which is above the median for nondiabetic subjects of all ethnic groups in the IRAS. Using this definition, the proportion of insulin-sensitive diabetic subjects was very low in all ethnic groups (non-Hispanic whites [14.3%] vs. African-Americans [6.5%], P = 0.039 in Los Angeles and Oakland; non-Hispanic whites [6.8%] vs. Hispanics [4.9%], P = 0.737 in San Luis Valley and San Antonio). These results were also similar in newly diagnosed mildly hyperglycemic diabetic subjects. In addition, these results were not affected by the adjustment for differences in obesity, body fat distribution, and severity of hyperglycemia. Even in nonobese subjects (with BMI <30 kg/m2), the proportion of insulin-sensitive subjects (S(I) > or =1.61 min-1 x microU-1 x ml-1) was low (3.6-9.7%). The acute insulin response (AIR) was significantly higher in African-Americans than in non-Hispanic whites; there were no ethnic differences in AIR between Hispanics and non-Hispanic whites. There were no significant ethnic differences for non-insulin-mediated glucose disposal (S(G)). We conclude that the number of insulin-sensitive NIDDM subjects is low and similar among non-Hispanic whites, Hispanics, and African-Americans in the U.S.

An approach for the use of Doppler ultrasound as a screening tool for hemodynamically significant stenosis (despite heterogeneity of Doppler performance). A multicenter experience. Asymptomatic Carotid Atherosclerosis Study Investigators

BACKGROUND AND PURPOSE

The Asymptomatic Carotid Atherosclerosis Study (ACAS) Doppler validation study assessed the performance of individual Doppler machines across a spectrum of laboratories. We attempted to establish a threshold specific to individual machines to predict angiographically defined hemodynamic stenosis. The reliability of these Doppler ultrasound criteria was prospectively and independently evaluated among patients screened with ultrasound in the ACAS trial.

METHODS

Regression techniques were used to establish the relationship between Doppler velocity and percent stenosis by angiography for 63 specific Doppler machines. This relationship was used to establish a Doppler threshold to provide a 90% positive predictive value (PPV) of a 60% stenosis by angiography. The sensitivity of each Doppler machine to detect a 60% stenosis (at the 90% PPV threshold) was estimated. The efficacy of these Doppler thresholds was then prospectively evaluated by calculating the PPV among ACAS participants eligible by ultrasound.

RESULTS

Of the 63 machines, 13 (21%) had an excellent sensitivity (80%+) at 90% PPV. In 32 devices (51%) only a marginal sensitivity (50% to 80%) could be achieved. In 9 devices (14%) the sensitivity was poor (0% to 50%), and in 9 (14%) no threshold could be established. Despite the heterogeneity of Doppler performance, the standardization program worked as designed in the ACAS trial. Of 825 surgical patients, 399 were eligible by Doppler and 395 subsequently underwent angiography. Of these, 32 (8.1%; 95% confidence interval, 5.4% to 10.8%) did not have hemodynamically significant stenosis by arteriography, a proportion nonsignificantly lower than the planned 10% by the PPV.

CONCLUSIONS

The performance of Doppler ultrasound was highly variable. This suggests that Doppler performance is likely overstated in the literature, but specific devices may perform satisfactorily to detect individuals with hemodynamically significant stenosis. Because performance differs substantially among devices, local investigators are strongly urged to maintain local standardization series. With such standardization, ultrasound performance is sufficient for admission to clinical trials and as the is sufficient for admission to clinical trials and as the basis for carotid surgery. However, without quality control many ultrasound machines are not adequate to accurately predict the degree of carotid stenosis and should not be the only test to decide whether surgery is warranted.

In vivo phenobarbital treatment increases protein binding to a putative AP-1 site in the CYP2B2 promoter

Phenobarbital (PB) is a potent inducer of cytochrome P450 enzymes, particularly CYP2B1/2B2. Although the mechanism(s) of PB induction of CYP2B1/2B2 is not fully understood, current research is focusing on the role PB may play in altering the binding of nuclear proteins to critical DNA response elements in the 5'-flanking region of these genes. In this study, rat liver nuclear proteins were analyzed for DNA binding ability using both a general consensus and a CYP2B2 sequence-specific AP-1 oligonucleotide. We demonstrate that in vivo PB treatment enhances protein binding activity to the consensus AP-1 oligonucleotide. Likewise, a putative AP-1 site, identified at -1441 in the CYP2B2 5'-flanking region, also formed a sequence specific DNA/protein complex which was enhanced after PB exposure. These data may support a role of AP-1 in the PB induction mechanism of CYP2B1/2B2.

Ethnic differences in carotid wall thickness. The Insulin Resistance Atherosclerosis Study

BACKGROUND AND PURPOSE

Ethnic differences in cardiovascular disease (CVD) morbidity and mortality have been observed in US adults. However, little data exist on differences in indices of preclinical atherosclerosis such as carotid wall intima-media thickness (IMT) for US non-Hispanic whites, Hispanics, and blacks. This study was undertaken to determine whether there were ethnic differences in carotid wall IMT.

METHODS

Internal carotid artery (ICA) IMT and common carotid artery (CCA) IMT, indices of atherosclerosis, were assessed with the use of B-mode ultrasound in 1020 nondiabetic participants in the Insulin Resistance Atherosclerosis Study, a multicenter study designed to examine the association between insulin resistance and carotid atherosclerosis. The study included 281 blacks, 329 Hispanics, and 410 non-Hispanic whites aged 40 to 69 years.

RESULTS

Blacks had significantly greater CCA IMT than non-Hispanic whites (865 versus 808 microns); this remained significant after adjustment for major CVD risk factors and insulin sensitivity (864 versus 823 microns). There were no significant differences in ICA IMT between blacks and non-Hispanic whites. Hispanics had significantly lesser CCA IMT than non-Hispanic whites (749 versus 776 microns), and these differences remained significant after adjustment for traditional cardiovascular risk factors and insulin sensitivity (750 versus 778 microns). There were no significant differences in ICA IMT between non-Hispanic whites and Hispanics.

CONCLUSIONS

We conclude that ethnic differences exist in CCA but not in ICA IMT in nondiabetic subjects. These differences in IMT, which are indicators of atherosclerosis, are a non-invasive measure that is consistent with some of the data on clinical end points. These differences may be associated with the observed differences in CVD morbidity and mortality among major ethnic groups in the United States.

Apolipoprotein E polymorphism is associated with segment-specific extracranial carotid artery intima-media thickening

BACKGROUND AND PURPOSE

Apolipoprotein E (apoE) polymorphism affects plasma cholesterol and may influence risk of atherosclerosis. We investigated the association of apoE with carotid artery wall thickening (an index of atherosclerosis) in individuals with and without coronary artery disease (CAD).

METHODS

ApoE phenotypes were resolved in 260 individuals equally represented by angiographically determined CAD case subjects and disease-free control subjects. Carotid artery intima-media thickening (IMT) was evaluated by B-mode ultrasound. Associations of apoE (E2, E3, or E4) with risk factors and IMT were evaluated in general linear models adjusted for age, sex, and CAD status with and without other traditional risk factors.

RESULTS

Total cholesterol (TC) and LDL cholesterol were associated with apoE isoforms. Mean TC and LDL cholesterol were lower in E2 (n = 33) carriers than E3 (n = 155) and E4 (n = 66) carriers (each P < .001). IMT also varied by apoE. E2 carriers had less common carotid IMT than E3 and E4 carriers (P < .01), while internal carotid IMT was less in E2 and E3 carriers than in E4 carriers (P < .02). Bifurcation IMT was not associated with apoE (P = .24). ApoE polymorphism remained associated with common (P < .01) and internal (P < .04) IMT, and the association of apoE with mean IMT of all sites reached significance (P < .04) after adjustment for age, sex, CAD status, TC, LDL cholesterol, HDL cholesterol, triglycerides, diabetes, hypertension, and smoking.

CONCLUSIONS

ApoE polymorphism is associated with segment specific carotid IMT. The association of apoE with carotid IMT was statistically independent of apoE-associated variation in LDL cholesterol levels.

Hypertension and subclinical carotid artery atherosclerosis in blacks and whites. The Atherosclerosis Risk in Communities Study. ARIC Investigators

OBJECTIVE

To describe the distribution of hypertension and its association with subclinical atherosclerosis in blacks and whites.

DESIGN

Population-based survey of 15,587 middle-aged adults from the Atherosclerosis Risk in Communities Study. Ultrasound-measured carotid artery intima media thickness (IMT) was used to estimate atherosclerosis. Hypertension was defined by the revised fifth Joint National Committee categories. Continuous systolic and diastolic blood pressure measurements also were evaluated.

RESULTS

Among participants not reporting use of antihypertensive medication, 43% to 52% of black and 68% to 78% of white participants had optimal to high-normal blood pressure across the 4 study centers; 11% to 22% of black and 6% to 9% of white participants had stage I or higher hypertension. Use of antihypertensive medications was reported by 34% to 45% of blacks and 20% of whites; 11% to 17% of blacks had stage I or higher hypertension compared with 4% to 7% of whites when treated. Higher hypertension categories were associated with thicker intima medias in all ethnic and gender groups, in participants who did and did not use medications. In participants who did not use medications, multiple linear regression models adjusted for diastolic blood pressure and other risk factors found that systolic blood pressure was positively associated with IMT except in black men; diastolic blood pressure was not related to IMT in blacks and had a negative relation with IMT in white men and a J-shaped relation with IMT in white women. Results of similar direction and magnitude were found in participants who used medications.

CONCLUSIONS

Hypertension was higher in blacks than whites and was associated with subclinical atherosclerosis. The association of atherosclerosis with hypertension is accounted for predominantly by systolic blood pressure. The intriguing negative association of diastolic blood pressure and atherosclerosis implies that pulse pressure may be an important correlate of atherosclerosis.

Tobacco farmers and diversification: opportunities and barriers

OBJECTIVE

To assess the knowledge, attitudes, and behaviours of tobacco growers and allotment owners in the southeastern United States.

DESIGN

Cross-sectional telephone survey.

PARTICIPANTS

Tobacco growers (n = 529) and tobacco allotment owners (n = 417) were interviewed by telephone in March 1995.

SETTING

Tobacco growing states in the southeastern US.

MAIN OUTCOME MEASURES

Attitudes of tobacco growers and tobacco allotment owners towards, and experience with, diversification; and attitudes towards an increase in the federal excise tax on tobacco.

RESULTS

Half of the respondents had done something to learn about on-farm alternatives to tobacco, had an interest in trying other on-farm ventures to supplement tobacco income, and found alternatives that were profitable. There was a strong, negative linear trend between age and being interested in or trying alternative enterprises. Structural and economic impediments to diversification were noted by respondents (especially younger respondents), but 73% supported an increase in the federal excise tax on tobacco if the money was used to help farmers overcome these barriers.

CONCLUSIONS

These data suggest that farmers and health professionals have reason to establish dialogue around diversification and using excise tax increases to fund diversification and to promote health. Tobacco companies have been successful in mobilising farmers against tax increases, but efforts must be made to show farmers that tax increases can be beneficial both to their diversification efforts and to public health. The outcome of this dialogue may well affect the economic infrastructure of thousands of rural communities, the livelihood of tens of thousands of tobacco farmers and their families, and the health of millions of tobacco users.

Increased insulin resistance and insulin secretion in nondiabetic African-Americans and Hispanics compared with non-Hispanic whites. The Insulin Resistance Atherosclerosis Study

The etiology of NIDDM is still controversial, with both insulin resistance and decreased insulin secretion postulated as potential important factors. African-Americans and Hispanics have a two- to threefold excess risk of developing NIDDM compared with non-Hispanic whites. Yet little is known concerning the prevalence of insulin resistance and secretion defects in minorities, especially in African-Americans in population-based studies. Fasting and 2-h post-glucose load glucose and insulin levels, insulin-mediated glucose disposal (insulin sensitivity index) (S(I)), glucose effectiveness (S(G)), and first-phase insulin response (acute insulin response [AIR]) were determined in nondiabetic African-Americans (n= 288), Hispanics (n= 363), and non-Hispanic whites (n= 435) as part of the Insulin Resistance Atherosclerosis Study. Subjects received a standard 2-h oral glucose tolerance test on the first day and an insulin-modified frequently sampled intravenous glucose tolerance test on the second day. African-Americans and Hispanics were more obese than non-Hispanic whites. Both African-Americans and Hispanics had higher fasting and 2-h insulin concentrations and AIR but lower S(I) than non-Hispanic whites. No ethnic difference was observed in S(G). After further adjustments for obesity, body fat distribution, and behavioral factors, African-Americans continued to have higher fasting and 2-h insulin levels and AIR, but lower S(I) than non-Hispanic whites. In contrast, after adjustment for these covariates, no significant ethnic differences in S(I) or fasting insulin levels were observed between Hispanics and non-Hispanic whites. Hispanics continued to have higher 2-h insulin levels and AIRs than those in non-Hispanic whites. In this report, the association between S(I) and upper body adiposity (waist-to-hip, ratio) was similar in each ethnic group. Both nondiabetic African-Americans and Hispanics have increased insulin resistance and higher AIR than nondiabetic non-Hispanic whites, suggesting that greater insulin resistance may be in large part responsible for the higher prevalence of NIDDM in these minority groups. However, in Hispanics. the greater insulin resistance may be due to greater adiposity and other behavioral factors.