Determination of Local Densities in Accreted Ice Samples Using X-Rays and Digital Imaging

At the NASA Lewis Research Center's Icing Research Tunnel ice shapes, similar to those which develop in-flight icing conditions, were formed on an airfoil. Under cold room conditions these experimental samples were carefully removed from the airfoil, sliced into thin sections, and x-rayed. The resulting microradiographs were developed and the film digitized using a high resolution scanner to extract fine detail in the radiographs. A procedure was devised to calibrate the scanner and to maintain repeatability during the experiment. The techniques of image acquisition and analysis provide accurate local density measurements and reveal the internal characteristics of the accreted ice with greater detail. This paper will discuss the methodology by which these samples were prepared with emphasis on the digital imaging techniques

The association of reduced lung function with blood pressure variability in African Americans: data from the Jackson Heart Study

Background African Americans (AAs) have lower lung function, higher blood pressure variability (BPV) and increased risk for hypertension and cardiovascular disease (CVD) compared with whites. The mechanism through which reduced lung-function is associated with increased CVD risk is unclear. Methods We evaluated the association between percent predicted lung-function and 24-hour BPV in 1008 AAs enrolled in the Jackson Heart Study who underwent ambulatory blood pressure (BP) monitoring. Lung-function was assessed as forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and the ratio of FEV1-to-FVC during a pulmonary function test using a dry rolling sealed spirometer and grouped into gender-specific quartiles. The pairwise associations of these three lung-function measures with two measures of 24-hour BPV, (1) day-night standard deviation (SDdn) and (2) average real variability (ARV) were examined for systolic BP (SBP) and, separately, diastolic BP (DBP). Results SDdn of SBP was not associated with FEV1 (mean ± standard deviation from lowest-to-highest quartile: 9.5 ± 2.5, 9.4 ± 2.4, 9.1 ± 2.3, 9.3 ± 2.6; p-trend = 0.111). After age and sex adjustment, the difference in SDdn of SBP was 0.0 (95 % CI −0.4,0.4), −0.4 (95 % CI −0.8,0.1) and −0.3 (95 % CI −0.7,0.1) in the three progressively higher versus lowest quartiles of FEV1 (p-trend = 0.041). Differences in SDdn of SBP across FEV1 quartiles were not statistically significant after further multivariable adjustment. After multivariable adjustment, no association was present between FEV1 and ARV of SBP or SDdn and ARV of DBP or when evaluating the association of FVC and FEV1-to-FVC with 24-hour BPV. Conclusion Lung-function was not associated with increased 24-hour BPV

Ambulatory blood pressure monitoring phenotypes among individuals with and without diabetes taking antihypertensive medication: the Jackson Heart Study

Ambulatory blood pressure monitoring (ABPM) can detect phenotypes associated with increased cardiovascular disease (CVD) risk. Diabetes is associated with increased CVD risk but few data are available documenting whether blood pressure (BP) phenotypes, detected by ABPM, differ between individuals with versus without diabetes. We conducted a cross-sectional analysis of 567 participants in the Jackson Heart Study, a population-based study of African Americans, taking antihypertensive medication to evaluate the association between diabetes and ABPM phenotypes. Two clinic BP measurements were taken at baseline following a standardized protocol. ABPM was performed for 24 h following the clinic visit. ABPM phenotypes included daytime, sustained, nocturnal and isolated nocturnal hypertension, a non-dipping BP pattern, and white coat, masked and masked isolated nocturnal hypertension. Diabetes was defined as fasting glucose greater than or equal to126 mg dl−1, haemoglobin A1c greater than or equal to6.5% (48 mmol mol−1) or use of insulin or oral hypoglycaemic medications. Of the included participants (mean age 62.3 years, 71.8% female), 196 (34.6%) had diabetes. After multivariable adjustment, participants with diabetes were more likely to have daytime hypertension (prevalence ratio (PR): 1.32; 95% confidence interval (CI): 1.09–1.60), masked hypertension (PR: 1.46; 95% CI: 1.11–1.93) and masked isolated nocturnal hypertension (PR: 1.39; 95% CI: 1.02–1.89). Although nocturnal hypertension was more common among participants with versus without diabetes, this association was not present after adjustment for daytime systolic BP. Diabetes was not associated with the other ABPM phenotypes investigated. This study highlights the high prevalence of ABPM phenotypes among individuals with diabetes taking antihypertensive medication

Association Between High Perceived Stress Over Time and Incident Hypertension in Black Adults: Findings From the Jackson Heart Study.

Background Chronic psychological stress has been associated with hypertension, but few studies have examined this relationship in blacks. We examined the association between perceived stress levels assessed annually for up to 13 years and incident hypertension in the Jackson Heart Study, a community-based cohort of blacks. Methods and Results Analyses included 1829 participants without hypertension at baseline (Exam 1, 2000-2004). Incident hypertension was defined as blood pressure≥140/90 mm Hg or antihypertensive medication use at Exam 2 (2005-2008) or Exam 3 (2009-2012). Each follow-up interval at risk of hypertension was categorized as low, moderate, or high perceived stress based on the number of annual assessments between exams in which participants reported "a lot" or "extreme" stress over the previous year (low, 0 high stress ratings; moderate, 1 high stress rating; high, ≥2 high stress ratings). During follow-up (median, 7.0 years), hypertension incidence was 48.5%. Hypertension developed in 30.6% of intervals with low perceived stress, 34.6% of intervals with moderate perceived stress, and 38.2% of intervals with high perceived stress. Age-, sex-, and time-adjusted risk ratios (95% CI) associated with moderate and high perceived stress versus low perceived stress were 1.19 (1.04-1.37) and 1.37 (1.20-1.57), respectively (P trend<0.001). The association was present after adjustment for demographic, clinical, and behavioral factors and baseline stress (P trend=0.001). Conclusions In a community-based cohort of blacks, higher perceived stress over time was associated with an increased risk of developing hypertension. Evaluating stress levels over time and intervening when high perceived stress is persistent may reduce hypertension risk

Sedentary behavior and subclinical atherosclerosis in African Americans: cross-sectional analysis of the Jackson heart study

BACKGROUND: Previous studies have reported conflicting results as to whether an association exists between sedentary time and cardiovascular disease (CVD) risk among African Americans. These studies, however, were limited by lack of consideration of sedentary behavior in leisure versus non-leisure settings. To elucidate this relation, we investigated the associations of television (TV) viewing time and occupational sitting with carotid intima-media thickness (CIMT), a subclinical atherosclerosis measure, in a community-based sample of African Americans. METHODS: We studied 3410 participants from the Jackson Heart Study, a single-site, community-based study of African Americans residing in Jackson, MS. CIMT was assessed by ultrasonography and represented mean far-wall thickness across right and left sides of the common carotid artery. TV viewing time, a measure of leisure sedentary behavior, and occupational sitting, a measure of non-leisure sedentary behavior, were assessed by questionnaire. RESULTS: In a multivariable regression model that included physical activity and CVD risk factors, longer TV viewing time (2-4 h/day and >4 h/day) was associated with greater CIMT (adjusted mean ± SE difference from referent [4 h/day; P-trend =0.001). In contrast, more frequent occupational sitting ('sometimes' and 'often/always') was associated with lower CIMT (adjusted mean ± SE difference from referent ['never/seldom']:-0.021 ± 0.009 mm for 'sometimes', and-0.018 ± 0.008 mm for 'often/always'; P-trend = 0.042). CONCLUSIONS: Longer TV viewing time was associated with greater CIMT, while occupational sitting was associated with lower CIMT. These findings suggest the role of sedentary behaviors in the pathogenesis of CVD among African Americans may vary by whether individuals engage in leisure versus non-leisure sedentary behaviors

The combined effects of genetic risk and perceived discrimination on blood pressure among African Americans in the Jackson Heart Study

Both genomics and environmental stressors play a significant role in increases in blood pressure (BP). In an attempt to further explain the hypertension (HTN) disparity among African Americans (AA), both genetic underpinnings (selected candidate genes) and stress due to perceived racial discrimination (as reported in the literature) have independently been linked to increased BP among AAs. Although Gene x Environment interactions on BP have been examined, the environmental component of these investigations has focused more on lifestyle behaviors such as smoking, diet, and physical activity, and less on psychosocial stressors such as perceived discrimination

Distribution of cardiovascular health by individual- and neighborhood-level socioeconomic status: Findings from the Jackson Heart Study

BACKGROUND: Data demonstrate a positive relationship between socioeconomic status (SES) and cardiovascular health (CVH). OBJECTIVE: To assess the association between individual- and neighborhood-level SES and CVH among participants of the JHS (Jackson Heart Study), a community-based cohort of African Americans in Jackson, Mississippi. METHODS: We included all JHS participants with complete SES and CVH information at the baseline study visit (n = 3,667). We characterized individual- and neighborhood-level SES according to income (primary analysis) and education (secondary analysis), respectively. The outcome of interest for these analyses was a CVH score, based on 7 modifiable behaviors and factors, summed to a total of 0 (worst) to 14 (best) points. We utilized generalized estimating equations to account for the clustering of participants within the same residential areas to estimate the linear association between SES and CVH. RESULTS: The median age of the participants was 55 years, and 64% were women. Nearly one-third of eligible participants had individual incomes \u3c$20,000 and close to 40$25,480). Adjusted for age, sex, and neighborhood SES, there was an average increase in CVH score of 0.31 points associated with each 1-category increase in individual income. Similarly, each 1-category increase in neighborhood SES was associated with a 0.19-point increase in CVH score. These patterns held for our secondary analyses, which used educational attainment in place of income. These data did not suggest a synergistic effect of individual- and neighborhood-level SES on CVH. CONCLUSIONS: Our findings suggest a potential causal pathway for disparities in CVH among vulnerable populations. These data can be useful to the JHS community to empower public health and clinical interventions and policies for the improvement of CVH

Physical Activity and Incident Hypertension in African Americans: The Jackson Heart Study

There is limited empirical evidence to support the protective effects of physical activity in the prevention of hypertension among African Americans. The purpose of this study was to examine the association of physical activity with incident hypertension among African Americans. We studied 1311 participants without hypertension at baseline enrolled in the Jackson Heart Study, a community-based study of African Americans residing in Jackson, Mississippi. Overall physical activity, moderate–vigorous physical activity, and domain-specific physical activity (work, active living, household, and sport/exercise) were assessed by self-report during the baseline examination (2000–2004). Incident hypertension, assessed at examination 2 (2005–2008) and examination 3 (2009–2013), was defined as the first visit with systolic/diastolic blood pressure ≥140/90 mm Hg or self-reported antihypertensive medication use. Over a median follow-up of 8.0 years, there were 650 (49.6%) incident hypertension cases. The multivariable-adjusted hazard ratios (95% confidence interval) for incident hypertension comparing participants with intermediate and ideal versus poor levels of moderate–vigorous physical activity were 0.84 (0.67–1.05) and 0.76 (0.58–0.99), respectively (P trend=0.038). A graded, dose–response association was also present for sport/exercise-related physical activity (Quartiles 2, 3, and 4 versus Quartile 1: 0.92 [0.68–1.25], 0.87 [0.67–1.13], 0.75 [0.58–0.97], respectively; P trend=0.032). There were no statistically significant associations observed for overall physical activity, or work, active living, and household-related physical activities. In conclusion, the results of the current study suggest that regular moderate–vigorous physical activity or sport/exercise-related physical activity may reduce the risk of developing hypertension in African Americans

Historical Redlining, Socioeconomic Distress, and Risk of Heart Failure Among Medicare Beneficiaries.

BACKGROUND: The association of historical redlining policies, a marker of structural racism, with contemporary heart failure (HF) risk among White and Black individuals is not well established. METHODS: We aimed to evaluate the association of redlining with the risk of HF among White and Black Medicare beneficiaries. Zip code-level redlining was determined by the proportion of historically redlined areas using the Mapping Inequality Project within each zip code. The association between higher zip code redlining proportion (quartile 4 versus quartiles 1-3) and HF risk were assessed separately among White and Black Medicare beneficiaries using generalized linear mixed models adjusted for potential confounders, including measures of the zip code-level Social Deprivation Index. RESULTS: A total of 2 388 955 Medicare beneficiaries (Black n=801 452; White n=1 587 503; mean age, 71 years; men, 44.6%) were included. Among Black beneficiaries, living in zip codes with higher redlining proportion (quartile 4 versus quartiles 1-3) was associated with increased risk of HF after adjusting for age, sex, and comorbidities (risk ratio, 1.08 [95% CI, 1.04-1.12]; P<0.001). This association remained significant after further adjustment for area-level Social Deprivation Index (risk ratio, 1.04 [95% CI, 1.002-1.08]; P=0.04). A significant interaction was observed between redlining proportion and Social Deprivation Index (Pinteraction<0.01) such that higher redlining proportion was significantly associated with HF risk only among socioeconomically distressed regions (above the median Social Deprivation Index). Among White beneficiaries, redlining was associated with a lower risk of HF after adjustment for age, sex, and comorbidities (risk ratio, 0.94 [95% CI, 0.89-0.99]; P=0.02). CONCLUSIONS: Historical redlining is associated with an increased risk of HF among Black patients. Contemporary zip code-level social determinants of health modify the relationship between redlining and HF risk, with the strongest relationship between redlining and HF observed in the most socioeconomically disadvantaged communities