Biomedical subjects

Lloyd E Chambless

Publications and source records attributed to Lloyd E Chambless.

At least 19 recordsLinked to original sources

PubMed2007

The association of the ankle-brachial index with incident coronary heart disease: the Atherosclerosis Risk In Communities (ARIC) study, 1987-2001.

BACKGROUND: Peripheral arterial disease (PAD), defined by a low ankle-brachial index (ABI), is associated with an increased risk of cardiovascular events, but the risk of coronary heart disease (CHD) over the range of the ABI is not well characterized, nor described for African Americans. METHODS: The ABI was measured in 12186 white and African American men and women in the Atherosclerosis Risk in Communities Study in 1987-89. Fatal and non-fatal CHD events were ascertained through annual telephone contacts, surveys of hospital discharge lists and death certificate data, and clinical examinations, including electrocardiograms, every 3 years. Participants were followed for a median of 13.1 years. Age- and field-center-adjusted hazard ratios (HRs) were estimated using Cox regression models. RESULTS: Over a median 13.1 years follow-up, 964 fatal or non-fatal CHD events accrued. In whites, the age- and field-center-adjusted CHD hazard ratio (HR, 95% CI) for PAD (ABI<0.90) was 2.81 (1.77-4.45) for men and 2.05 (1.20-3.53) for women. In African Americans, the HR for men was 4.86 (2.76-8.47) and for women was 2.34 (1.26-4.35). The CHD risk increased exponentially with decreasing ABI as a continuous function, and continued to decline at ABI values > 1.0, in all race-gender subgroups. The association between the ABI and CHD relative risk was similar for men and women in both race groups. A 0.10 lower ABI increased the CHD hazard by 25% (95% CI 17-34%) in white men, by 20% (8-33%) in white women, by 34% (19-50%) in African American men, and by 32% (17-50%) in African American women. CONCLUSION: African American members of the ARIC cohort had higher prevalences of PAD and greater risk of CHD associated with ABI-defined PAD than did white participants. Unlike in other cohorts, in ARIC the CHD risk failed to increase at high (>1.3) ABI values. We conclude that at this time high ABI values should not be routinely considered a marker for increased CVD risk in the general population. Further research is needed on the value of the ABI at specific cutpoints for risk stratification in the context of traditional risk factors.

Black or African American↗

PubMed2006

Estimation of time-dependent area under the ROC curve for long-term risk prediction.

Sensitivity, specificity, and area under the ROC curve (AUC) are often used to measure the ability of survival models to predict future risk. Estimation of these parameters is complicated by the fact that these parameters are time-dependent and by the fact that censoring affects their estimation just as it affects estimation of survival curves or coefficients of survival regression models. The authors present several estimators that overcome these complications. One approach is a recursive calculation over the ordered times of events, analogous to the Kaplan-Meier approach to survival function estimation. Another is to first apply Bayes' theorem to write the parameters of interest in terms of conditional survival functions that are then estimated by survival analysis methods. Simulation studies demonstrate that the proposed estimators perform well in practical situations, when compared with an estimator (c-statistic, from logistic regression) that ignores time. An illustration with data from a cardiovascular follow-up study is provided.

Area Under Curve↗

PubMed2006

Food group intake and brain lesions in late-life vascular depression.

BACKGROUND: Studies indicate that diet may be related to the occurrence of brain lesions. The cross-sectional association between food intake and brain lesion volumes in late-life depression was examined in a cohort of elderly individuals with current or prior depression. METHODS: Food intake was assessed in 54 elderly vascular depression subjects (vascular depression defined by presence of hyperintensities on brain MRI) using a Block 1998 food frequency questionnaire. Food and kilocalorie intake were determined. Brain lesion volumes were calculated from MRI. Subjects were aged 60 or over and were participants in a longitudinal study of major depression. All subjects received psychiatric assessment and treatment, and medical comorbidity assessments. RESULTS: High-fat dairy and whole grains were significantly positively correlated with brain lesion volume, while other food groups were not significantly associated with lesion volume. In multivariable analyses, controlling for age, sex, hypertension, diabetes and total kilocalories, the positive association with lesion volume remained significant for both high-fat dairy and whole grains. CONCLUSIONS: High fat dairy and whole grain consumption may be associated with brain lesions in elderly subjects with depression.

Age of Onset↗

PubMed2006

Risk factors for ischemic stroke subtypes: the Atherosclerosis Risk in Communities study.

BACKGROUND AND PURPOSE: To evaluate risk factors for ischemic stroke by its subtypes may contribute to more effective prevention of ischemic stroke, but few prospective studies have characterized risk factors for specific subtypes of ischemic stroke. METHODS: Between 1987 and 1989, 14,448 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. The incidence of stroke was ascertained from hospital surveillance records. RESULTS: During an average follow-up of 13.4-years, 531 incident ischemic strokes occurred (105 lacunar, 326 nonlacunar, and 100 cardioembolic). Blacks had a 3-fold higher multivariate-adjusted risk ratio of lacunar stroke compared with whites. No racial difference in nonlacunar or cardioembolic strokes was found after adjusting for prevalent risk factors. In addition to traditional risk factors, nontraditional risk factors, such as waist-to-hip ratio, history of coronary heart disease, left ventricular hypertrophy, lipoprotein(a), and von Willebrand factor, were associated with increased risk for nonlacunar stroke, whereas lacunar stroke was related to only 1 nontraditional risk factor, white blood cell count. The population-attributable fraction (PAF) for hypertension was approximately 35% for all ischemic stroke subtypes. The respective PAFs for diabetes and current smoking were 26.3% and 22.0% for lacunar versus 11.3% and 11.4% for nonlacunar stroke. The PAF for elevated von Willebrand factor was greater than that for current smoking for cardioembolic stroke. CONCLUSIONS: The impact of traditional and nontraditional risk factors other than hypertension on the incidence of ischemic stroke varied according to its subtype.

Black or African American↗

PubMed2006

An assessment of incremental coronary risk prediction using C-reactive protein and other novel risk markers: the atherosclerosis risk in communities study.

BACKGROUND: There has been interest in recent years in whether additional, and in particular novel, risk factors or blood markers, such as C-reactive protein, can enhance existing coronary heart disease (CHD) prediction models. METHODS: Using a series of case-cohort studies, the prospective Atherosclerosis Risk in Communities (ARIC) Study assessed the association of 19 novel risk markers with incident CHD in 15,792 adults followed up since 1987-1989. Novel markers included measures of inflammation, endothelial function, fibrin formation, fibrinolysis, B vitamins, and antibodies to infectious agents. Change in the area under the receiver operating characteristic curve (AUC) was used to assess the additional contribution of novel risk markers to CHD prediction beyond that of traditional risk factors. RESULTS: The basic risk factor model, which included traditional risk factors (age, race, sex, total and high-density lipoprotein cholesterol levels, systolic blood pressure, antihypertensive medication use, smoking status, and diabetes), predicted CHD well, as evidenced by an AUC of approximately 0.8. The C-reactive protein level did not add significantly to the AUC (increase in AUC of 0.003), and neither did most other novel risk factors. Of the 19 markers studied, lipoprotein-associated phospholipase A(2), vitamin B(6), interleukin 6, and soluble thrombomodulin added the most to the AUC (range, 0.006-0.011). CONCLUSIONS: Our findings suggest that routine measurement of these novel markers is not warranted for risk assessment. On the other hand, our findings reinforce the utility of major, modifiable risk factor assessment to identify individuals at risk for CHD for preventive action.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2006

Lipoprotein(a) and incident ischemic stroke: the Atherosclerosis Risk in Communities (ARIC) study.

BACKGROUND AND PURPOSE: Numerous case-control and cross-sectional studies have reported higher median lipoprotein(a) [Lp(a)] levels among stroke patients than controls, but existing prospective studies have not consistently shown an association. We sought to examine the relationship between plasma Lp(a) levels and the incidence of ischemic stroke among blacks and whites. METHODS: Between 1987 and 1989, 14,221 men and women (3647 blacks and 10,574 whites) aged 45 to 64 years and free of clinical cardiovascular disease, took part in the first examination of the Atherosclerosis Risk in Communities (ARIC) study cohort. Lp(a) and other risk factors for cardiovascular disease were measured at baseline. RESULTS: During the 13.5-year follow-up, 496 ischemic strokes occurred. Participants with Lp(a) > or =300 microg/mL had a 79% higher age, sex, and race-adjusted rate ratio (RR) of ischemic stroke than did those with Lp(a) levels <100 microg/mL. Compared with Lp(a) <100 microg/mL, the multivariate adjusted RRs for Lp(a) > or =300 microg/mL were 1.84 (95% CI, 1.05 to 3.07) in black women, 1.72 (95% CI, 0.86 to 3.48) in black men, 2.42 (95% CI, 1.30 to 4.53) in white women, and 1.18 (95% CI, 0.47 to 2.90) in white men. There was no significant increment in the RRs for 100 to 199 microg/mL and 200 to 299 microg/mL groups. CONCLUSIONS: A high Lp(a) concentration is associated with a higher incidence of ischemic stroke in blacks and white women, but not in white men.

Black People↗

PubMed2006

The reliability of the ankle-brachial index in the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS).

BACKGROUND: A low ankle-brachial index (ABI) is associated with increased risk of coronary heart disease, stroke, and death. Regression model parameter estimates may be biased due to measurement error when the ABI is included as a predictor in regression models, but may be corrected if the reliability coefficient, R, is known. The R for the ABI computed from DINAMAP readings of the ankle and brachial SBP is not known. METHODS: A total of 119 participants in both the Atherosclerosis Risk in Communities (ARIC) study and the NHLBI Family Heart Study (FHS) had repeat ABIs taken within 1 year, using a common protocol, automated oscillometric blood pressure measurement devices, and technician pool. RESULTS: The estimated reliability coefficient for the ankle systolic blood pressure (SBP) was 0.68 (95% CI: 0.57, 0.77) and for the brachial SBP was 0.74 (95% CI: 0.62, 0.83). The reliability for the ABI based on single ankle and arm SBPs was 0.61 (95% CI: 0.50, 0.70) and the reliability of the ABI computed as the ratio of the average of two ankle SBPs to two arm SBPs was estimated from simulated data as 0.70. CONCLUSION: These reliability estimates may be used to obtain unbiased parameter estimates if the ABI is included in regression models. Our results suggest the need for repeated measures of the ABI in clinical practice, preferably within visits and also over time, before diagnosing peripheral artery disease and before making therapeutic decisions.

Ankle↗

PubMed2006

Does the impact of smoking on coronary heart disease differ by low-density lipoprotein cholesterol level?: the Atherosclerosis Risk in Communities (ARIC) Study.

BACKGROUND: The association of smoking with coronary heart disease (CHD) occurrence has been reported to be weaker for populations with lower plasma cholesterol levels. Recent studies suggest that low-density lipoprotein cholesterol (LDL-C) and smoking contribute to different stages of atherosclerosis, so the present study was designed to test the hypothesis that smoking is a stronger risk factor for CHD when LDL-C is high. METHODS AND RESULTS: The study group of 13,410 middle-aged adults who were initially free of stroke and CHD were followed and over 13.3 years there were 932 incident CHD events. Tests for multiplicative interaction were performed using proportional hazards models. Both smoking and increased LDL-C were risk factors for CHD incidence. The relative hazard (RH) of CHD in relation to smoking tended to be larger among higher LDL-C categories compared with lower LDL-C categories. For example, when the participants were dichotomized into 4 categories, using smoking >or=15 cigarettes per day and LDL-C >or=130 mg/dl as cutoffs, those with high LDL-C and heavier cigarette smoking showed a very high RH of CHD (RH =2.81) compared with that expected from the product of the RHs of high LDL-C (RH =1.15) only x heavy smoking only (RH =1.71) (p for interaction =0.04). CONCLUSIONS: These results suggest positive multiplicative interactions between smoking and LDL-C for CHD incidence.

Cholesterol, LDL↗

PubMed2005

Lipoprotein-associated phospholipase A2, high-sensitivity C-reactive protein, and risk for incident ischemic stroke in middle-aged men and women in the Atherosclerosis Risk in Communities (ARIC) study.

BACKGROUND: Measurement of inflammatory markers has been reported to identify individuals at increased risk for ischemic stroke. Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a proinflammatory enzyme secreted by macrophages. We assessed Lp-PLA2 and C-reactive protein (CRP) levels along with traditional risk factors to examine their relation to ischemic stroke. METHODS: A proportional hazards model was used in a prospective case-cohort study of 12,762 apparently healthy middle-aged men and women in the Atherosclerosis Risk in Communities (ARIC) study who were observed for about 6 years. RESULTS: Mean Lp-PLA2 and CRP levels adjusted for sex, race, and age were higher in the 194 stroke cases than the 766 noncases, whereas low-density lipoprotein cholesterol (LDL-C) level was not significantly different. Both Lp-PLA2 and CRP levels were associated with ischemic stroke after adjustment for age, sex, and race: hazard ratios were 2.23 for the highest vs the lowest tertile of Lp-PLA2 and 2.70 for CRP level higher than 3 vs lower than 1 mg/L. In a model that included smoking, systolic hypertension, lipid levels, and diabetes, Lp-PLA2 and CRP levels in the highest category were associated with hazard ratios of 1.91 (95% confidence interval, 1.15-3.18; P = .01) and 1.87 (95% confidence interval, 1.13-3.10; P = .02), respectively. Individuals with high levels of both CRP and Lp-PLA2 were at the highest risk after adjusting for traditional risk factors compared with individuals with low levels of both, whereas others were at intermediate risk. CONCLUSION: Levels of Lp-PLA2 and CRP may be complementary beyond traditional risk factors in identifying middle-aged individuals at increased risk for ischemic stroke.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed2005

Plasma total homocysteine levels in stroke patients screened for the vitamin intervention for stroke prevention clinical trial in the era of folate fortification.

Folic acid fortification of grain products was mandated in the USA by January 1998 and in Canada by November 1998. It was hypothesized that screening total plasma homocysteine levels adjusted for age, sex, race and country that were drawn in stroke patients for the Vitamin Intervention for Stroke Prevention trial from 1997 to 2001 would be steady when fortification was completed. Samples were grouped by years 1997/1998, 1999 and 2000/2001, and adjusted means were calculated using a general linear regression model. In 2,612 US and 1,059 Canadian patients, levels showed no consistent trend in the USA alone, while Canadian levels declined (p = 0.06 overall, 0.0003 in the oldest age group). US levels were 0.39 micromol/l (95% CI: -0.08, 0.85) lower than in Canada. Neither fasting nor time since stroke affected the results.

Adult↗

PubMed2005

Vitamin Intervention For Stroke Prevention trial: an efficacy analysis.

BACKGROUND AND PURPOSE: The Vitamin Intervention for Stroke Prevention trial (VISP) intention-to-treat analysis did not show efficacy of combined vitamin therapy for recurrent vascular events in patients with nondisabling stroke. Reasons for lack of efficacy may have included folate fortification of grain products, inclusion of the recommended daily intake for B12 in the low-dose arm, treatment with parenteral B12 in patients with low B12 levels in both study arms, a dose of B12 too low for patients with malabsorption, supplementation with nonstudy vitamins, and failure of patients with significant renal impairment to respond to vitamin therapy. We conducted an efficacy analysis limited to patients most likely to benefit from the treatment, based on hypotheses arising from evidence developed since VISP was initiated. The criteria for this subgroup were defined before any data analysis. METHODS: For this analysis, we excluded patients with low and very high B12 levels at baseline (<250 and >637 pmol/L, representing the 25th and 95th percentiles), to exclude those likely to have B12 malabsorption or to be taking B12 supplements outside the study and patients with significant renal impairment (glomerular filtration rate <46.18; the 10th percentile). RESULTS: This subgroup represents 2155 patients (37% female), with a mean age of 66+/-10.7 years. For the combined end point of ischemic stroke, coronary disease, or death, there was a 21% reduction in the risk of events in the high-dose group compared with the low-dose group (unadjusted P=0.049; adjusted for age, sex, blood pressure, smoking, and B12 level P=0.056). In Kaplan-Meier survival analysis comparing 4 groups, patients with a baseline B12 level at the median or higher randomized to high-dose vitamin had the best overall outcome, and those with B12 less than the median assigned to low-dose vitamin had the worst (P=0.02 for combined stroke, death, and coronary events; P=0.03 for stroke and coronary events). CONCLUSIONS: In the era of folate fortification, B12 plays a key role in vitamin therapy for total homocysteine. Higher doses of B12, and other treatments to lower total homocysteine may be needed for some patients.

Aged↗

PubMed2005

Prediction of coronary events in a low incidence population. Assessing accuracy of the CUORE Cohort Study prediction equation.

BACKGROUND: The aims of this paper are to derive a 10-year coronary risk predictive equation for adult Italian men, and to assess its accuracy in comparison with the Framingham Heart Study (FHS) and PROCAM study equations. METHODS: The CUORE study is a prospective fixed-cohort study. Eleven cohorts, from the north and the centre-south of Italy, had been investigated at baseline between 1982 and 1996, adopting MONICA methods to measure risk factors. Among this sample of 6865 men, aged 35-69 years and free of coronary heart disease (CHD) at baseline, 312 first fatal and non-fatal major coronary events occurred in 9.1 years median follow-up. Calibration, as the difference between 10-year predicted and actual risk, and discrimination, as the ability of the risk functions to separate high-risk from low-risk subjects, have been assessed to compare accuracy of the FHS, the PROCAM, and the CUORE study equations. RESULTS: The best CUORE equation includes age, total cholesterol, systolic blood pressure, cigarette smoking, HDL-cholesterol, diabetes mellitus, hypertension drug treatment, and family history of CHD (area under the ROC curve = 0.75). The uncalibrated estimates of the 10-year risk in this CUORE follow-up data were 0.093 and 0.109 higher (P < 0.05) from the Framingham and PROCAM risk scores, respectively, than the Kaplan-Meier estimate for CUORE, indicating risk overestimates for both equations. Standard recalibration techniques improved accuracy of the FHS equation only. PROCAM overestimates were prominent in the higher risk deciles. With an alternative method for recalibration better risk estimates were obtained, but a cohort study was needed to obtain a properly calibrated risk equation. CONCLUSIONS: The CUORE Project predictive equation showed better accuracy of the FHS and PROCAM equations, overcoming frequently reported risk overestimates. The CUORE equation may be adopted to identify men with high coronary risk in Italy.

Adult↗

PubMed2005

The association of spatial T wave axis deviation with incident coronary events. The ARIC cohort.

BACKGROUND: Although current evidence suggests that the spatial T wave axis captures important information about ventricular repolarization abnormalities, there are only a few and discordant epidemiologic studies addressing the ability of the spatial T wave axis to predict coronary heart disease (CHD) occurrence. METHODS: This prospective study analyzed data from 12,256 middle-aged African American and white men and women, from the Atherosclerosis Risk in Communities Study (ARIC). Following a standardized protocol, resting standard 12-lead, 10-second electrocardiograms were digitized and analyzed with the Marquette GE program. The median follow-up time was 12.1 years; incident coronary heart disease comprised fatal and non-fatal CHD events. RESULTS: The incidence rate of CHD was 4.26, 4.18, 4.28 and 5.62 per 1000 person-years respectively, across the spatial T wave axis quartiles. Among women for every 10 degrees increase in the spatial T wave axis deviation, there was an estimated increase in the risk of CHD of 1.16 (95% CI 1.04-1.28). After adjustment for age, height, weight, smoking, hypertension, diabetes, QRS axis and minor T wave abnormalities, this hazard rate ratio for women fell to 1.03 (0.92-1.14). The corresponding crude and adjusted hazard ratios for men were 1.05 (95% CI 0.96-1.15) and 0.95 (0.86-1.04) respectively. CONCLUSIONS: In conclusion, this prospective, population-based, bi-ethnic study of men and women free of coronary heart disease at baseline shows that spatial T wave axis deviation is not associated with incident coronary events during long-term follow up. It is doubtful that spatial T wave axis deviation would add benefit in the prediction of CHD events above and beyond the current traditional risk factors.

Black or African American↗

PubMed2005

Risk factors for cardiovascular event recurrence in the Atherosclerosis Risk in Communities (ARIC) study.

BACKGROUND: Numerous studies have identified risk factors and markers associated with incidence of cardiovascular disease (CVD). However, few studies have examined whether established risk factors, novel blood markers, carotid ultrasonography, or ankle-brachial index can predict recurrent CVD events. METHODS AND RESULTS: We analyzed the relation of established risk factors and markers of atherosclerosis with the risk of recurrent CVD in 766 participants. Over a mean of 8.7 years of follow-up, 70 women and 243 men had a recurrent CVD event (85.3% coronary heart disease and 23.7% stroke). Adjusting for age and sex, this study found that established risk factors were associated with recurrent CVD events in the anticipated direction. Being in the highest (vs lowest) quartiles of lipoprotein (a), fibrinogen, white blood cells, and creatinine at baseline were associated with 47%, 69%, 65%, and 81%, respectively, greater risk of a CVD event, and being in the highest quartile of albumin was associated with 39% lower risk. Being in the highest (vs lowest) quartile of carotid intima-media thickness (IMT) was associated with a doubling of risk, and having carotid plaque with acoustic shadowing (vs having no plaque) was associated with 83% increased risk of a CVD event. After adjustment for established risk factors, creatinine, albumin, and carotid IMT in the highest quartile (vs lowest quartile) and carotid plaque with acoustic shadowing (vs no plaque) were independently associated with recurrent CVD events. CONCLUSION: Established risk factors, but only a few of novel risk factors and markers, were independent predictors of recurrent CVD events.

Atherosclerosis↗

PubMed2005

Lower extremity arterial disease assessed by ankle-brachial index in a middle-aged population of African Americans and whites: the Atherosclerosis Risk in Communities (ARIC) Study.

BACKGROUND: Lower extremity arterial disease (LEAD) is one of the most common manifestations of atherosclerosis. Its epidemiologic characteristics have not been well described, particularly in African Americans. Our purpose was to estimate the prevalence of LEAD and its associations with cardiovascular risk factors in a biracial population of men and women aged 45 to 64 years. METHODS: We examined 15,173 African-American and white men and women who participated in the baseline examination (1987-1989) of the Atherosclerosis Risk in Communities (ARIC) Study. LEAD was defined by a resting ankle-brachial index (ABI), the ratio of ankle systolic blood pressure to brachial systolic pressure, of < or = 0.90. Cross-sectional analyses were used to determine the association of LEAD with cardiovascular risk factors. RESULTS: The age-adjusted prevalence of ABI < or = 0.90 was 3.1% in African-American men, 4.4% in African-American women, 2.3% in white men, and 3.2% in white women. Cigarette smoking was the single most important risk factor for prevalent LEAD. The odds ratio estimate for LEAD in ever smokers versus never smokers was 6.6 (95% confidence interval [CI]=2.0-21.5) in African-American men, 2.3 (95% CI=1.5-3.5) in African-American women, 10.4 (95% CI=3.8-28.3) in white men, and 1.9 (95% CI=1.4-2.6) in white women, after adjustment for age, LDL cholesterol, hypertension, and diabetes. Prevalent LEAD was also associated with hypertension, diabetes, and higher concentrations of total cholesterol, triglycerides, LDL-cholesterol, and fibrinogen, and lower concentrations of HDL cholesterol, but the associations were not always significant across race/ethnic and gender groups. The associations of LEAD with plasma lipids were generally stronger in African Americans than whites. CONCLUSIONS: The prevalence of LEAD appears to be higher in African Americans than whites. Elevations in traditional cardiovascular risk factors are associated with a higher prevalence of LEAD across race/ethnic and gender groups.

Black or African American↗

PubMed2005

Short-term repeatability of electrocardiographic spatial T-wave axis and QT interval.

Although ventricular repolarization abnormalities reflect arrhythmic susceptibility, few reliable tools exist to identify their presence. We investigated the repeatability of the spatial T-wave axis and QT interval from standard 12-lead electrocardiograms in 63 asymptomatic volunteers. Certified technicians used a standardized protocol to digitally record 2 electrocardiograms per participant at each of 2 visits separated by 1 to 2 weeks. Absolute paired differences within and between visits were 0.19 degrees and 0.90 degrees for the T-wave axis and 1.08 and 1.55 milliseconds for the QT interval, respectively. The intraclass correlation coefficients for the T-wave axis and QT interval were 0.87 and 0.86, respectively. The impact of repeated measurements on the precision of the QT-interval measurements was evaluated for a hypothetical clinical trial aimed at detecting a drug-induced QT prolongation. We conclude that the spatial T-wave axis is as repeatable a measure of ventricular repolarization as the QT interval.

Electrocardiography↗

PubMed2005

Diabetes, glucose, insulin, and heart rate variability: the Atherosclerosis Risk in Communities (ARIC) study.

OBJECTIVE: To describe the progression of autonomic impairment among individuals with diabetes and pre-diabetic metabolic impairments. RESEARCH DESIGN AND METHODS: We investigated the consequence of diabetes and pre-diabetic metabolic impairments on the 9-year change in heart rate variability (HRV) in a population-based cohort of 6,245 individuals aged 45-64 years at baseline and cross-sectional associations among 9,940 individuals. RESULTS: Diabetic subjects had a more rapid temporal decrease in HRV conditional on baseline HRV than nondiabetic subjects. Adjusted mean annual changes (95% CI) (ms/year) in the SD of all normal-to-normal R-R intervals were -0.65 (-0.69 to -0.61) for those with normal fasting glucose vs. -0.95 (-1.09 to -0.81) for diabetic subjects, in root mean square of successive differences in normal-to-normal R-R intervals -0.35 (-0.39 to -0.30) vs. -0.66 (-0.82 to -0.51), and in R-R interval 6.70 (6.37-7.04) vs. 3.89 (2.72-5.05). While we found cross-sectional associations between decreased HRV and diabetes and nondiabetic hyperinsulinemia and a weak inverse association with fasting glucose, neither impaired fasting glucose nor nondiabetic hyperinsulimenia was associated with a measurably more rapid decline in HRV than normal. CONCLUSIONS: Cardiac autonomic impairment appears to be present at early stages of diabetic metabolic impairment, and progressive worsening of autonomic cardiac function over 9 years was observed in diabetic subjects. The degree to which pre-diabetic metabolic impairments in insulin and glucose metabolism contribute to decreases in cardiac autonomic function remains to be determined.

Arteriosclerosis↗

PubMed2005

Identifying individuals at high risk for diabetes: The Atherosclerosis Risk in Communities study.

OBJECTIVE: To develop and evaluate clinical rules to predict risk for diabetes in middle-aged adults. RESEARCH DESIGN AND METHODS: The Atherosclerosis Risk in Communities is a cohort study conducted from 1987-1989 to 1996-1998. We studied 7,915 participants 45-64 years of age, free of diabetes at baseline, and ascertained 1,292 incident cases of diabetes by clinical diagnosis or oral glucose tolerance testing. RESULTS: We derived risk functions to predict diabetes using logistic regression in a random half of the sample. Rules based on these risk functions were evaluated in the other half. A risk function based on waist, height, hypertension, blood pressure, family history of diabetes, ethnicity, and age was performed similarly to one based on fasting glucose (area under the receiver-operating characteristic curve [AUC] 0.71 and 0.74, respectively; P = 0.2). Risk functions composed of the clinical variables plus fasting glucose (AUC 0.78) and additionally including triglycerides and HDL cholesterol (AUC 0.80) performed better (P < 0.001). Evaluation of scores based on the metabolic syndrome as defined by the National Cholesterol Education Program or with slight variations showed AUCs of 0.75 and 0.78, respectively. Rules based on all these approaches, while identifying 20-56% of the sample as screen positive, achieved sensitivities of 40-87% and specificities of 50-86%. CONCLUSIONS: Rules derived from clinical information, alone or combined with simple laboratory measures, can characterize degrees of diabetes risk in middle-aged adults, permitting preventive actions of appropriate intensity. Rules based on the metabolic syndrome are reasonable alternatives to rules derived from risk functions.

Arteriosclerosis↗