Chad Blackshear

Prevalence and changes over time of ideal cardiovascular health metrics among African–Americans: The Jackson Heart Study

OBJECTIVES The aim of this study is to assess the prevalence and changes over time of ideal Lifes Simple Seven (LSS) in African-Americans. METHODS Prospective cohort of 5301 African-Americans from the Jackson Heart Study (JHS) from 2000 to 2013. Each of the LSS metrics was categorized as poor, intermediate, or ideal. RESULTS Among men, the prevalence of having 0, 1, 2, 3, 4, 5, 6, and 7 ideal LSS was 3.3%, 23.0%, 33.5%, 24.7%, 11.6%, 3.6%, 0.3%, and 0%, respectively. Corresponding values for women were 1.7%, 26.3%, 33.1%, 22.8%, 11.9%, 3.7%, 0.6%, and 0%. Prevalence of ideal diet was 0.9%. The proportions of those meeting LSS ideal recommendations for cholesterol and fasting glucose declined from the first through third JHS visits across all age groups, whereas prevalence of ideal BMI declined only in participants <40 years at a given visit. Prevalence of ideal blood pressure did not change over time and being ideal on physical activity improved from the first [18.3% (95% CI: 17.3% to 19.3%)] to third visit [24.8% (95% CI: 23.3% to 26.3%)]. CONCLUSIONS Our data show a low prevalence of ideal LSS (especially diet, physical activity, and obesity) in the JHS and a slight improvement in adherence to physical activity recommendations over time.

Ideal Cardiovascular Health and Incident Cardiovascular Events: The Jackson Heart Study

INTRODUCTION The epidemiology of American Heart Association ideal cardiovascular health (CVH) metrics has not been fully examined in African Americans. This study examines the associations of CVH metrics with incident cardiovascular disease (CVD) in the Jackson Heart Study, a longitudinal cohort study of CVD in African Americans. METHODS Jackson Heart Study participants without CVD (n=4,702) were followed prospectively between 2000 and 2011. Incidence rates and Cox proportional hazard ratios estimated risks for incident CVD (myocardial infarction, stroke, cardiac procedures, and CVD mortality) associated with seven CVH metrics by sex. Analyses were performed in 2015. RESULTS Participants were followed for a median of 8.3 years; none had ideal health on all seven CVH metrics. The prevalence of ideal health was low for nutrition, physical activity, BMI, and blood pressure metrics. The age-adjusted CVD incidence rate (IR) per 1,000 person years was highest for individuals with the least ideal health metrics: zero to one (IR=12.5, 95% CI=9.7, 16.1), two (IR=8.2, 95% CI=6.5, 10.4), three (IR=5.7, 95% CI=4.2, 7.6), and four or more (IR=3.4, 95% CI=2.0, 5.9). Adjusting for covariates, individuals with four or more ideal CVH metrics had lower risks of incident CVD compared with those with zero or one ideal CVH metric (hazard ratio, 0.29; 95% CI=0.17, 0.52; p<0.001). CONCLUSIONS African Americans with more ideal CVH metrics have lower risks of incident CVD. Comprehensive preventive behavioral and clinical supports should be intensified to improve CVD risk for African Americans with few ideal CVH metrics.

Resting Heart Rate and Long-term Outcomes Among the African American Population: Insights From the Jackson Heart Study.

Importance Increased resting heart rate is associated with worse outcomes in studies of mostly white populations, but its significance is not well established in African Americans persons whose cardiac comorbidities and structural abnormalities differ. Objective To study the prognostic utility of heart rate in a community-based African American cohort in the Jackson Heart Study. Design, Setting, and Participants A total of 5261 participants in the Jackson Heart Study, a prospective, community-based study in Jackson, Mississippi, were evaluated. Baseline heart rate was assessed by quintiles and as a continuous variable. All participants with baseline heart rate documented by a 12-lead electrocardiogram without pacing or atrial fibrillation noted on their baseline Jackson Heart Study examination were included in the study. Follow-up began September 26, 2000, and was completed December 31, 2011. Data analysis was performed from July to October 2015. Main Outcomes and Measures Unadjusted and adjusted associations between heart rate and all-cause mortality and heart failure hospitalization using Cox proportional hazards regression models. Results Of the 5261 individuals included in the analysis, 1921 (36.5%) were men; median (25th-75th percentile) age was 55.7 (45.4-64.8) years. Median (25th-75th percentile) baseline heart rate was 63 beats per minute (bpm) (57-71 bpm). The highest heart rate quintile (73-118 bpm) had higher rates of diabetes (398 [37.4%]; P < .001) and hypertension (735 [69.1%]; P < .001), higher body mass index (median [IQR], 32.4 [28.1-38.3]; P < .001), less physical activity (0 hours per week, 561 [52.8%]; P < .001), and lower &bgr;-blocker use (73 [6.9%]; P < .001) compared with lower quintiles. Caffeine intake (from 80.7 to 85.5 mg/d; P = .57) and left ventricular ejection fraction (from 62% to 62.3%; P = .01) were similar between groups. As a continuous variable, elevated heart rate was associated with increased mortality and heart failure hospitalizations, with adjusted hazard ratios for every 5-bpm increase of 1.14 (95% CI, 1.10-1.19) and 1.10 (95% CI, 1.05-1.16), respectively. Similar patterns were observed in comparisons between the highest and lowest quintiles. Conclusions and Relevance Higher baseline heart rate was associated with increased mortality and heart failure hospitalizations among African American participants in the Jackson Heart Study. These findings are similar to those seen in white populations, but further study is needed to understand whether African American individuals benefit from interventions targeting heart rate reduction.

Pericardial fat volume and incident atrial fibrillation in the Multi-Ethnic Study of Atherosclerosis and Jackson Heart Study

To determine whether greater pericardial fat volume would be associated with increased risk of incident atrial fibrillation (AF).

Prediction of Incident Diabetes in the Jackson Heart Study Using High-Dimensional Machine Learning

Statistical models to predict incident diabetes are often based on limited variables. Here we pursued two main goals: 1) investigate the relative performance of a machine learning method such as Random Forests (RF) for detecting incident diabetes in a high-dimensional setting defined by a large set of observational data, and 2) uncover potential predictors of diabetes. The Jackson Heart Study collected data at baseline and in two follow-up visits from 5,301 African Americans. We excluded those with baseline diabetes and no follow-up, leaving 3,633 individuals for analyses. Over a mean 8-year follow-up, 584 participants developed diabetes. The full RF model evaluated 93 variables including demographic, anthropometric, blood biomarker, medical history, and echocardiogram data. We also used RF metrics of variable importance to rank variables according to their contribution to diabetes prediction. We implemented other models based on logistic regression and RF where features were preselected. The RF full model performance was similar (AUC = 0.82) to those more parsimonious models. The top-ranked variables according to RF included hemoglobin A1C, fasting plasma glucose, waist circumference, adiponectin, c-reactive protein, triglycerides, leptin, left ventricular mass, high-density lipoprotein cholesterol, and aldosterone. This work shows the potential of RF for incident diabetes prediction while dealing with high-dimensional data.

Comparison of risk scores for the prediction of stroke in African Americans: Findings from the Jackson Heart Study

BACKGROUND Evidence from existing cohort studies supports the prediction of incident coronary heart disease and stroke using 10-year cardiovascular disease (CVD) risk scores and the American Heart Association/American Stroke Associations cardiovascular health (CVH) metric. METHODS We included all Jackson Heart Study participants with complete scoring information at the baseline study visit (2000-2004) who had no history of stroke (n = 4,140). We used Kaplan-Meier methods to calculate the cumulative incidence of stroke and used Cox models to estimate hazard ratios and 95% CIs for stroke according to CVD risk and CVH score. We compared the discrimination of the 2 models according to the Harrell c index and plotted predicted vs observed stroke risk calibration plots for each of the 2 models. RESULTS The median age of the African American participants was 54.5 years, and 65% were female. The cumulative incidence of stroke increased across worsening categories of CVD risk and CVH. A 1-unit increase in CVD risk increased the hazard of stroke (1.07, 1.06-1.08), whereas each 1-unit increase in CVH corresponded to a decreased hazard of stroke (0.76, 0.69-0.83). As evidenced by the c statistics, the CVH model was less discriminating than the CVD risk model (0.59 [0.55-0.64] vs 0.79 [0.76-0.83]). CONCLUSIONS Both scores were associated with incident stroke in a dose-response fashion; however, the CVD risk model was more discriminating than the CVH model. The CVH score may still be preferable for its simplicity in application to broad patient populations and public health efforts.

Restrictive Spirometry Pattern, Cardiac Structure and Function, and Incident Heart Failure in African Americans. The Jackson Heart Study

Rationale: Although chronic obstructive pulmonary disease has been related to heart failure, the relationship between the restrictive spirometry pattern (forced vital capacity [FVC] < 80% predicted with preserved forced expiratory volume in 1 second [FEV1]/FVC ratio) and heart failure is poorly understood. Objectives: To determine whether having a restrictive spirometry pattern is associated with incident heart failure hospitalization. Methods: Community‐dwelling African Americans from the Jackson Heart Study (total n = 5,306; analyzed n = 4,210 with spirometry and heart failure outcome data) were grouped by restrictive spirometry (FEV1/FVC ≥ 0.70, FVC < 80%; n = 840), airflow obstruction (FEV1/FVC < 0.70; n = 341), and normal spirometry (FEV1/FVC ≥ 0.70, FVC ≥ 80%; n = 3,029) at the time of baseline examination in 2000‐2004. We assessed relationships of echocardiographic parameters and biomarkers with spirometry patterns using regression models. Incident heart failure was defined as an adjudicated hospitalization for heart failure after January 1, 2005 in subjects with no self‐reported heart failure history. We used multivariable‐adjusted Poisson regression models and Cox proportional hazards models, with death treated as a competing risk in the Cox models, to test associations between spirometry patterns and incident heart failure. We also modeled the association of FVC% predicted with heart failure hospitalization risk using a restricted cubic spline after excluding subjects with airflow obstruction. Results: At the time of baseline spirometry, participants with restrictive spirometry had a median age of 57.2 years (interquartile range, 47.8‐64.1); 38.1% were male. Compared with normal spirometry, restrictive spirometry was associated with a higher transmitral early (E) wave velocity to atrial (A) wave velocity ratio, higher pulmonary artery systolic pressure, and higher endothelin levels. After a median follow‐up time of 8.0 years, 8.0% of subjects with restrictive spirometry (n = 67) had developed incident heart failure, compared with 3.8% of those with normal spirometry (n = 115) and 10.6% of those with airflow obstruction (n = 36). After risk adjustment, both a restrictive pattern (hazard ratio [HR], 1.5; 95% confidence interval [CI], 1.1‐2.0) and airflow obstruction (HR, 1.7; 95% CI, 1.1‐2.5) were associated with increased rates of incident heart failure hospitalization compared with normal spirometry. Using flexible modeling, the lowest hazards of heart failure hospitalization were observed around FVC 90‐100%, with lower FVC% values associated with an increased incidence of heart failure. Conclusions: Both a restrictive pattern on spirometry and airflow obstruction identify African Americans with impaired lung health at risk for heart failure.

Fatty Liver Disease, Women, and Aldosterone: Finding a Link in the Jackson Heart Study

Context: Fatty liver disease is one of the most common forms of chronic liver disease. The renin-angiotensin-aldosterone system has been implicated in the pathogenesis of fatty liver. Objective: Determine the relationship between fatty liver and aldosterone in a large cohort study. Design: Community-based, observational cohort study of African Americans. Setting: The original Jackson Heart Study cohort enrolled African American participants from the Jackson, Mississippi, metropolitan area in Hinds, Madison, and Rankin Counties. Participants: Our study population consisted of 2507 Jackson Heart Study participants (1625 women and 882 men) who had liver attenuation measured per computed tomography scans, had aldosterone measurements, and were not taking angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or mineralocorticoid receptor antagonists. Intervention: There was no intervention. Main outcome measure: Liver attenuation on computed tomography scans. Results: Univariate regression analysis demonstrated a statistically significant correlation between aldosterone levels and liver attenuation. Each doubling of aldosterone was associated with 1.08 Hounsfield unit decrease (95% confidence interval, 1.47 to −0.69, P < 0.001). A multivariable model adjusted for body mass index, age, alcohol intake, and homeostatic model assessment of insulin resistance determined that the association was statistically significant only for women. Conclusion: Our data demonstrate a positive association between aldosterone levels and fatty liver in African American women.

Atrial Fibrillation in an African-American Cohort: the Jackson Heart Study

Atrial fibrillation (AF) is an important public health problem across race/ethnic groups. Data from US cohort studies initiated in the 1980s suggest a higher prevalence of AF risk factors among African‐Americans (AAs) than whites, but lower AF incidence. The Jackson Heart Study (JHS) is a community‐based study of 5306 AAs recruited starting in 2000.

Relation of Carotid Intima-Media Thickness to Cardiovascular Events in Black Americans (From the Jackson Heart Study)

Although several prospective studies have reported independent relations between carotid intima-media thickness (CIMT) and risk of incident cardiovascular diseases (CVD) in primarily non-African-American (AA) cohorts, the utility of CIMT values for the prediction of incident coronary heart disease and stroke events in blacks remain unclear. At the baseline examination (2000 to 2004) of the Jackson Heart Study, AA adults 21 to 94 years of age (mean 54) underwent bilateral far-wall CIMT measurement (mean 0.76 mm). Incident CVD events were then assessed over 7 to 11 years of follow-up (2000 to 2011) from samples of 2,463 women (107 CVD events) and 1,338 men (64 CVD events) who were free of clinical CVD at baseline. Each 0.2-mm increase in CIMT was associated with age-adjusted incident CVD hazard ratios of 1.4 (95% confidence interval 1.2, 1.5) for women and 1.3 (1.1, 1.6) for men. Classification accuracy improved only slightly when comparing multivariable models that used traditional risk factors alone with models that added CIMT: C-statistics 0.837 (0.794, 0.881) versus 0.842 (0.798, 0.886) in women and 0.754 (0.683, 0.826) versus 0.763 (0.701, 0.825) in men. Similarly, risk reclassification was only mildly improved by adding CIMT: Net Reclassification Index 0.13 (p = 0.05) and 0.05 (p = 0.50) for women and men, respectively; Integrated Discrimination Improvement 0.02 (p = 0.02) and 0.01 (p = 0.26) for women and men, respectively. In conclusion, CIMT was associated with incident CVD but provided modest incremental improvement in risk reclassification beyond traditional risk factors in a community-based AA cohort.