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1.  Complex systems thinking and current impasses in health disparities research 
American Journal of Public Health  2011;101(9):1627-1634.
Complex systems approaches have received increasing attention in public health because reductionist approaches yield limited insights in the context of dynamic systems. Most discussions to date have been highly abstract. There is a need to consider the application of complex systems approaches to specific research questions. After briefly reviewing the features of population health problems for which complex systems approaches are most likely to yield new insights, this commentary discusses possible applications of complex systems to health disparities research. It provides illustrative examples of how complex systems approaches may help address unanswered and persistent questions regarding genetic factors, life course processes, place effects, and the impact of upstream policies. It is argued that the concepts and methods of complex systems may help researchers move beyond current impasse points in health disparities research.
PMCID: PMC3154209  PMID: 21778505
2.  Neighborhood Characteristics and Leukocyte Telomere Length: The Multi-Ethnic Study of Atherosclerosis 
Health & place  2014;28:167-172.
Telomeres are the protective caps at the ends of eukaryotic chromosomes. Telomeres get shorter each time a cell divides, and critically shortened telomeres trigger cellular senescence. Thus, telomere length is hypothesized to be a biological marker of aging. The purpose of this study was to examine the association between neighborhood characteristics and leukocyte telomere length. Using data from a subsample (n=978) of the Multi-Ethnic Study of Atherosclerosis, a population-based study of women and men aged 45–84, we found that neighborhood social environment (but not neighborhood socioeconomic disadvantage) was associated with telomere length. Respondents who lived in neighborhoods characterized by lower aesthetic quality, safety, and social cohesion had shorter telomeres than those who lived in neighborhoods with a more salutary social environment, even after adjusting for individual-level socioeconomic status and biomedical and lifestyle factors related to telomere length. Telomere length may be one biological mechanism by which neighborhood characteristics influence an individual’s risk of disease and death.
PMCID: PMC4096814  PMID: 24859373
neighborhood socioeconomic disadvantage; neighborhood social environment; telomere length; cell aging
3.  Association of Neighborhood Characteristics with Cardiovascular Health in the Multi-Ethnic Study of Atherosclerosis (MESA) 
The concept of ‘cardiovascular health’ (CVH) was introduced as a global measure of one’s cardiovascular health. Previous studies established the relationship between neighborhood characteristics and individual cardiovascular risk factors. However, the relationship between neighborhood environment and overall CVH remains unknown.
Methods and Results
We analyzed data from the MESA baseline exam (2000–2002). Mean age was 61.6 years and 52% were female. Ideal, intermediate and poor categories of cholesterol, body mass index, diet, physical activity, fasting glucose, blood pressure and smoking were defined according to the AHA 2020 Strategic Goals, assigned an individual score and summed to create an overall score. CVH scores were categorized into ideal (11–14 points), intermediate (9–10) and poor (0–8). Neighborhood exposures included favorable food store and physical activity resources densities (by 1-mile buffer), reported healthy food availability, walking/physical activity environment, safety and social cohesion (by census tract). Multinomial logistic regression was used to determine the association of each characteristic with ideal and intermediate CVH, adjusted for demographics and neighborhood socioeconomic status (SES). Over 20% of MESA participants had an ideal CVH score at baseline. In fully adjusted models, favorable food stores (OR= 1.22, 1.06–1.40), physical activity resources (OR=1.19, 1.08–1.31), walking/physical activity environment (OR=1.20, 1.05–1.37) and neighborhood SES (OR=1.22, 1.11–1.33) were associated with higher odds of having an ideal CVH score.
Neighborhood environment including favorable food stores, physical activity resources, walking/physical activity environment and neighborhood SES are associated with ideal CVH. Further research is needed to investigate the longitudinal associations between neighborhood environment and CVH.
PMCID: PMC4172357  PMID: 25006187
risk factors; blood pressure; cholesterol; diet; exercise; prevention
4.  The associations of fast food restaurant availability with dietary intake and weight among African Americans in the Jackson Heart Study, 2000–2004 
American Journal of Public Health  2011;101(Suppl 1):S301-S309.
The purpose of this study was to examine the associations of fast food restaurant (FFR) availability with dietary intake and weight among African Americans in the Southeastern United States.
Cross-sectional associations of 0.5, 1, 2, and 5 mile FFR availability with energy, fat, carbohydrates, fiber, and fruit and vegetable intakes, and body mass index (BMI) and waist circumference were investigated in 4,740 African American Jackson Heart Study participants (55.2±12.6 years, 63.3% women).
No consistent associations between FFR availability and BMI or waist circumference were observed. Greater FFR availability was associated with higher energy intake among persons <55 years after adjustment for individual socioeconomic status mean difference in energy intake per standard deviation increase in 5-mile FFR 138 KCal (Confidence interval (CI): 70.53, 204.75) and 58 Kcal (CI: 8.55, 105.97) in men and women, respectively. Similar associations were also observed for the 2-mile windows in men. FFR availability was positively associated with total fiber intake among men and women <55 years.
FFR availability may contribute to greater energy intake in younger African Americans.
PMCID: PMC3222494  PMID: 21551382
5.  A Test of Biological and Behavioral Explanations for Gender Differences in Telomere Length: The Multi-Ethnic Study of Atherosclerosis 
Biodemography and social biology  2014;60(2):156-173.
The purpose of this study was to examine biological and behavioral explanations for gender differences in leukocyte telomere length (LTL), a biomarker of cell aging that has been hypothesized to contribute to women’s greater longevity. Data are from a subsample (n = 851) of the Multi-Ethnic Study of Atherosclerosis, a population-based study of women and men aged 45 to 84. Mediation models were used to examine study hypotheses. We found that women had longer LTL than men, but the gender difference was smaller at older ages. Gender differences in smoking and processed meat consumption partially mediated gender differences in telomere length, whereas gender differences in estradiol, total testosterone, oxidative stress, and body mass index did not. Neither behavioral nor biological factors explained why the gender difference in LTL was smaller at older ages. Longitudinal studies are needed to assess gender differences in the rate of change in LTL over time; to identify the biological, behavioral, and psychosocial factors that contribute to these differences throughout the life course; and to determine whether gender differences in LTL explain the gender gap in longevity.
PMCID: PMC4460606  PMID: 25343364
6.  Association between Language and Risk Factor Levels among Hispanic Adults with Hypertension, Hypercholesterolemia, or Diabetes 
American heart journal  2009;157(1):53-59.
The association of acculturation and cardiovascular risk factor control among populations with high proportions of immigrants has not been well-studied.
We studied 1492 Hispanic participants in the Multi-Ethnic Study of Atherosclerosis (MESA) with hypertension, hypercholesterolemia, and/or diabetes. We used linear regression to examine the cross-sectional relationships between acculturation measures and cardiovascular risk factor levels. Outcome measures included systolic blood pressure (mmHg), fasting LDL-cholesterol (mg/dL), and fasting blood glucose (mg/dL). Covariates included education, income, health insurance, physical activity, dietary factors, risk factor-specific medication use, duration of medication use, smoking, and BMI.
There were 580 Hispanics with hypertension, 539 with hypercholesterolemia, and 248 with diabetes. After adjustment for age and gender, Spanish-speaking Hispanics with cardiovascular risk factors had higher systolic blood pressure, fasting LDL-cholesterol and fasting blood glucose compared to English-speaking Hispanics. Differences in systolic blood pressure were accounted for mainly by education, whereas differences in LDL-cholesterol were almost entirely accounted for by cholesterol-lowering medication use. Differences in fasting glucose were partly accounted for by socioeconomic variables but were augmented after adjustment for dietary factors. Similar associations were observed between proportion of life in the U.S. and risk factor levels.
Among those with cardiovascular risk factors, Hispanics who spoke Spanish at home and lived less time in the U.S. had worse control of cardiovascular risk factors. Treatment strategies that focus on Hispanics with low levels of acculturation may improve cardiovascular risk factor control.
PMCID: PMC4448120  PMID: 19081396
7.  Association between Stress Response Genes and Features of Diurnal Cortisol Curves in the Multi-Ethnic Study of Atherosclerosis: A New Multi-Phenotype Approach for Gene-Based Association Tests 
PLoS ONE  2015;10(5):e0126637.
The hormone cortisol is likely to be a key mediator of the stress response that influences multiple physiologic systems that are involved in common chronic disease, including the cardiovascular system, the immune system, and metabolism. In this paper, a candidate gene approach was used to investigate genetic contributions to variability in multiple correlated features of the daily cortisol profile in a sample of European Americans, African Americans, and Hispanic Americans from the Multi-Ethnic Study of Atherosclerosis (MESA). We proposed and applied a new gene-level multiple-phenotype analysis and carried out a meta-analysis to combine the ethnicity specific results. This new analysis, instead of a more routine single marker-single phenotype approach identified a significant association between one gene (ADRB2) and cortisol features (meta-analysis p-value=0.0025), which was not identified by three other commonly used existing analytic strategies: 1. Single marker association tests involving each single cortisol feature separately; 2. Single marker association tests jointly testing for multiple cortisol features; 3. Gene-level association tests separately carried out for each single cortisol feature. The analytic strategies presented consider different hypotheses regarding genotype-phenotype association and imply different costs of multiple testing. The proposed gene-level analysis integrating multiple cortisol features across multiple ethnic groups provides new insights into the gene-cortisol association.
PMCID: PMC4439141  PMID: 25993632
8.  Salivary Cortisol Protocol Adherence and Reliability by Sociodemographic Features: the Multi-Ethnic Study of Atherosclerosis 
Psychoneuroendocrinology  2014;43:30-40.
Collection of salivary cortisol has become increasingly popular in large population-based studies. However, the impact of protocol compliance on day-to-day reliabilities of measures, and the extent to which reliabilities differ systematically according to socio-demographic characteristics, has not been well characterized in large-scale population-based studies to date. Using data on 935 men and women from the Multi-ethnic Study of Atherosclerosis, we investigated whether sampling protocol compliance differs systematically according to socio-demographic factors and whether compliance was associated with cortisol estimates, as well as whether associations of cortisol with both compliance and socio-demographic characteristics were robust to adjustments for one another. We further assessed the day-to-day reliability for cortisol features and the extent to which reliabilities vary according to socio-demographic factors and sampling protocol compliance. Overall, we found higher compliance among persons with higher levels of income and education. Lower compliance was significantly associated with a less pronounced cortisol awakening response (CAR) but was not associated with any other cortisol features, and adjustment for compliance did not affect associations of socio-demographic characteristics with cortisol. Reliability was higher for area under the curve (AUC) and wake up values than for other features, but generally did not vary according to socio-demographic characteristics, with few exceptions. Our findings regarding intra-class correlation coefficients (ICCs) support prior research indicating that multiple day collection is preferable to single day collection, particularly for CAR and slopes, more so than wakeup and AUC. There were few differences in reliability by socio-demographic characteristics. Thus, it is unlikely that group-specific sampling protocols are warranted.
PMCID: PMC4029420  PMID: 24703168
Salivary cortisol; Cortisol awakening response (CAR); Diurnal cortisol; Reliability; Compliance; Population-based study
9.  Does academic achievement during childhood and adolescence benefit later health? 
Annals of epidemiology  2014;24(5):344-355.
Educational disparities in health persist after adjustment for income and occupation, suggesting that other purely cognitive and psychosocial mechanisms may be involved. Unlike occupation- or income-mediated effects, effects of cognitive and psychosocial gains—as reflected in academic achievement—may be apparent even before schooling is completed.
We used data spanning 10 years on a national U.S. cohort of 2,546 children aged 3–14 at baseline to estimate effects of academic achievement, measured by standardized tests of cognitive achievement, on future health. We used marginal structural models to address potential mutual influence of achievement and health on each other over time.
One standard deviation higher academic achievement 1997– 2002 was associated with a lower prevalence of poorer health status in 2007 in girls (prevalence ratio [PR] = 0.87 [(95% confidence interval) 0.78–0.97]) but not in boys (PR = 0.96 [0.86–1.08]). Higher achievement was also weakly associated with lower BMI and less psychological distress among girls only.
Academic achievement may benefit future health but a number of questions remain unanswered, including reasons for the gender differences and how academic-achievement-related health disparities may progress over the life course and interact with other social determinants of health.
PMCID: PMC4037140  PMID: 24792585
academic achievement; body mass index; children and adolescents; education; gender; health status; marginal structural models; mental health
10.  The association of optimism and pessimism with inflammation and hemostasis in the Multi-Ethnic Study of Atherosclerosis (MESA) 
Psychosomatic medicine  2010;72(2):134-140.
Optimism and pessimism are associated with cardiovascular disease mortality and progression, however the biological mechanism remains unclear. This study investigates the association between optimism/pessimism and concentrations of seven inflammation and hemostasis markers.
This cross-sectional study used data from the Multi-Ethnic Study of Atherosclerosis (MESA), a study of 6814 persons aged 45–84 with no history of clinical cardiovascular disease. The Life-Orientation Test—Revised (LOT-R) was used to measure dispositional optimism and pessimism. Regression analyses were used to estimate associations of optimism and pessimism with interleukin-6 (IL-6), C-reactive protein (CRP), fibrinogen, homocysteine, factor VIII, D-dimer, and plasmin-antiplasmin, before and after adjustment for sociodemographics, depression, cynicism, health behaviors, BMI, hypertension, and diabetes.
Higher scores on the LOT-R (positive disposition) were related to lower concentrations of IL-6 (p=0.001), fibrinogen (p<0.001) and homocysteine (p=0.031). Associations were stronger for the pessimism subscale. After adjustment for demographics, the percentage differences in inflammatory markers corresponding to a 2-standard deviation increase in pessimism were 6.01% (p=0.001) for IL-6; 10.31% (p=0.001) for CRP; 2.47% (p<0.0001) for fibrinogen, and 1.36% (p=0.07) for homocysteine. Associations were attenuated but significant after adjustment for sociodemographics, depression, cynical distrust, and behaviors. Further adjustment for hypertension, BMI and diabetes reduced associations for CRP and IL-6. Pessimism remained associated with a 1.36% (p=0.02) increase in fibrinogen in the fully adjusted model. Factor VIII, D-dimer and plasmin-antiplasmin were not associated with the LOT-R or subscales.
Pessimism is related to higher levels of inflammation. Health behaviors, BMI, hypertension and diabetes appear to play a mediating role.
PMCID: PMC2842951  PMID: 20100888
Psychosocial factors; inflammation; coagulation; epidemiology; risk factors
11.  Neighborhood Characteristics and Availability of Healthy Foods in Baltimore 
Differential access to healthy foods may contribute to racial and economic health disparities. The availability of healthy foods has rarely been directly measured in a systematic fashion. This study examines the associations among the availability of healthy foods and racial and income neighborhood composition.
A cross-sectional study was conducted in 2006 to determine differences in the availability of healthy foods across 159 contiguous neighborhoods (census tracts) in Baltimore City and Baltimore County and in the 226 food stores within them. A healthy food availability index (HFAI) was determined for each store, using a validated instrument ranging from 0 points to 27 points. Neighborhood healthy food availability was summarized by the mean HFAI for the stores within the neighborhood. Descriptive analyses and multilevel models were used to examine associations of store type and neighborhood characteristics with healthy food availability.
Forty-three percent of predominantly black neighborhoods and 46% of lower-income neighborhoods were in the lowest tertile of healthy food availability versus 4% and 13%, respectively, in predominantly white and higher-income neighborhoods (p<0.001). Mean differences in HFAI comparing predominantly black neighborhoods to white ones, and lower-income neighborhoods to higher-income neighborhoods, were −7.6 and −8.1, respectively. Supermarkets in predominantly black and lower-income neighborhoods had lower HFAI scores than supermarkets in predominantly white and higher-income neighborhoods (mean differences −3.7 and −4.9, respectively). Regression analyses showed that both store type and neighborhood characteristics were independently associated with the HFAI score.
Predominantly black and lower-income neighborhoods have a lower availability of healthy foods than white and higher-income neighborhoods due to the differential placement of types of stores as well as differential offerings of healthy foods within similar stores. These differences may contribute to racial and economic health disparities.
PMCID: PMC4348113  PMID: 18842389
12.  Cross-Sectional and Longitudinal Associations of Neighborhood Cohesion and Stressors with Depressive Symptoms in the Multiethnic Study of Atherosclerosis (MESA) 
Annals of epidemiology  2009;19(1):49-57.
This study examined associations of neighborhood social cohesion, violence and aesthetic quality with depressive symptoms amongst 2619 healthy adults aged 45-84 years enrolled in the Multiethnic Study of Atherosclerosis.
Neighborhood characteristics were estimated by surveying a separate sample of area residents. Measures of aesthetic environment, social cohesion, and violence were combined into a summary score with increasing scores indicating more favorable environments. Depressive symptoms were measured using the Center for Epidemiologic Studies Depression (CES-D) scale. Marginal maximum likelihood estimation was used to assess associations of neighborhood characteristics with CES-D score at baseline and with the odds of developing incident depression (CES-D score ≥16 or use of antidepressants) over a 4-5 year follow-up among persons with CESD<16 at baseline. Models were adjusted for age, income, education, and race/ethnicity.
Lower levels of social cohesion and aesthetic quality and higher levels of violence were associated with higher mean CES-D scores in men and women (p-value for trend <0.01, adjusted mean difference in CES-D per 1 SD increase in summary score -1.01 (95% CI: -1.85, -0.17) and -1.08 (-1.88, -0.28) in men and women respectively). Associations of neighborhood characteristics with incident depression were in the expected direction for women but confidence intervals were wide (OR of incident depression 0.89 (0.63, 1.26)). No association was seen for men (OR=0.96 (0.74, 1.25)). Conclusions: Neighborhood social cohesion, aesthetic quality and violence are associated with the presence of depressive symptoms in residents.
PMCID: PMC2763272  PMID: 19064189
mental health; depression; residence characteristics; epidemiology; social environment
13.  Associations of Acculturation and Socioeconomic Status with Subclinical CVD in the MultiEthnic Study of Atherosclerosis 
American journal of public health  2008;98(11):1963-1970.
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.
PMCID: PMC2575668  PMID: 18511718
14.  Race/ethnicity and telomere length in the Multi-Ethnic Study of Atherosclerosis 
Aging cell  2009;8(3):251-257.
Telomere length has emerged as a marker of exposure to oxidative stress and aging. Race/ethnic differences in telomere length have been infrequently investigated. Leucocyte telomere length (LTL) was assessed 981 white, black and Hispanic men and women aged 45-84 years participating in the Multi-Ethnic Study of Atherosclerosis. Direct measurement and questionnaire were used to assess covariates. Linear regression was used to estimate associations of LTL with race/ethnicity and age after adjustment for sex, income, education, smoking, physical activity, diet, and body mass index. On average blacks and Hispanics had shorter telomeres than whites (adjusted mean differences (standard error) in T/S ratio compared to whites: -0.041 (0.018) for blacks and -0.044 (0.018) for Hispanics). Blacks and Hispanics showed greater differences in telomere length associated with age than whites (adjusted mean differences in T/S ratio per one year increase in age -0.0018, -0.0047, and -0.0055 in whites, blacks, and Hispanics respectively). Differences in age associations were more pronounced and only statistically significant in women. Race/ethnic differences in LTL may reflect the cumulative burden of differential exposure to oxidative stress (and its predictors) over the lifecourse.
PMCID: PMC2713110  PMID: 19302371
Telomeres; race/ethnicity; aging
15.  Air Pollution and Percent Emphysema Identified by Computed Tomography in the Multi-Ethnic Study of Atherosclerosis 
Environmental Health Perspectives  2014;123(2):144-151.
Background: Air pollution is linked to low lung function and to respiratory events, yet little is known of associations with lung structure.
Objectives: We examined associations of particulate matter (PM2.5, PM10) and nitrogen oxides (NOx) with percent emphysema-like lung on computed tomography (CT).
Methods: The Multi-Ethnic Study of Atherosclerosis (MESA) recruited participants (45–84 years of age) in six U.S. states. Percent emphysema was defined as lung regions < –910 Hounsfield Units on cardiac CT scans acquired following a highly standardized protocol. Spirometry was also conducted on a subset. Individual-level 1- and 20-year average air pollution exposures were estimated using spatiotemporal models that included cohort-specific measurements. Multivariable regression was conducted to adjust for traditional risk factors and study location.
Results: Among 6,515 participants, we found evidence of an association between percent emphysema and long-term pollution concentrations in an analysis leveraging between-city exposure contrasts. Higher concentrations of PM2.5 (5 μg/m3) and NOx (25 ppb) over the previous year were associated with 0.6 (95% CI: 0.1, 1.2%) and 0.5 (95% CI: 0.1, 0.9%) higher average percent emphysema, respectively. However, after adjustment for study site the associations were –0.6% (95% CI: –1.5, 0.3%) for PM2.5 and –0.5% (95% CI: –1.1, 0.02%) for NOx. Lower lung function measures (FEV1 and FVC) were associated with higher PM2.5 and NOx levels in 3,791 participants before and after adjustment for study site, though most associations were not statistically significant.
Conclusions: Associations between ambient air pollution and percentage of emphysema-like lung were inconclusive in this cross-sectional study, thus longitudinal analyses may better clarify these associations with percent emphysema.
Citation: Adar SD, Kaufman JD, Diez-Roux AV, Hoffman EA, D’Souza J, Stukovsky KH, Rich SS, Rotter JI, Guo X, Raffel LJ, Sampson PD, Oron AP, Raghunathan T, Barr RG. 2015. Air pollution and percent emphysema identified by computed tomography in the Multi-Ethnic Study of Atherosclerosis. Environ Health Perspect 123:144–151;
PMCID: PMC4314244  PMID: 25302408
16.  Associations of the Local Food Environment with Diet Quality—A Comparison of Assessments based on Surveys and Geographic Information Systems 
American journal of epidemiology  2008;167(8):917-924.
There is growing interest in understanding how food environments affect diet, but characterizing the food environment is challenging. The authors investigated the relation between global diet measures (an empirically derived “fats and processed meats” (FPM) dietary pattern and the Alternate Healthy Eating Index (AHEI)) and three complementary measures of the local food environment: 1) supermarket density, 2) participant-reported assessments, and 3) aggregated survey responses of independent informants. Data were derived from the baseline examination (2000–2002) of the Multi-Ethnic Study of Atherosclerosis, a US study of adults aged 45–84 years. A healthy diet was defined as scoring in the top or bottom quintile of AHEI or FPM, respectively. The probability of having a healthy diet was modeled by each environment measure using binomial regression. Participants with no supermarkets near their homes were 25–46% less likely to have a healthy diet than those with the most stores, after adjustment for age, sex, race/ethnicity, and socioeconomic indicators: The relative probability of a healthy diet for the lowest store density category versus the highest was 0.75 (95% confidence interval: 0.59, 0.95) for the AHEI and 0.54 (95% confidence interval: 0.42, 0.70) for FPM. Similarly, participants living in areas with the worst-ranked food environments (by participants or informants) were 22–35% less likely to have a healthy diet than those in the best-ranked food environments. Efforts to improve diet may benefit from combining individual and environmental approaches.
PMCID: PMC2587217  PMID: 18304960
diet; food; residence characteristics; social class
17.  Availability of Recreational Resources in Minority and Low Socioeconomic Status Areas 
Differences in availability of recreational resources may contribute to racial and SES disparities in physical activity. Variations in the location and density of recreational resources were examined by SES and racial composition of neighborhoods.
Densities of resources available in recreational facilities and parks were estimated for census tracts between April 2003 and June 2004 in North Carolina, New York, and Maryland using kernel estimation. The probability of not having a facility or park was modeled by tract racial composition and SES, adjusting for population and area, using binomial regression in 2006. Mean densities of tract resources were modeled by SES and racial composition using linear regression.
Minority neighborhoods were significantly more likely than white neighborhoods not to have recreational facilities (relative probability (RP)=3.27 (95% CI=2.11–5.07) and 8.60 (95% CI=4.48–16.51), for black and Hispanic neighborhoods, respectively). Low-income neighborhoods were 4.5 times more likely to not have facilities than high-income areas (95% CI=2.87–7.12). Parks were more equitably distributed. Most resources located in recreational facilities required a fee and were less dense in minority and low-income areas. Those located inside parks were usually free to use, sports-related, and denser in poor and minority neighborhoods.
Recreational facilities and the resources they offer are not equitably distributed. The presence of parks in poor and minority areas suggest that improving the types and quality of resources in parks could be an important strategy to increase physical activity and reduce racial/ethnic and socioeconomic disparities.
PMCID: PMC2254179  PMID: 18083446
18.  Testing Departure from Additivity in Tukey’s Model using Shrinkage: Application to a Longitudinal Setting 
Statistics in medicine  2014;33(29):5177-5191.
While there has been extensive research developing gene-environment interaction (GEI) methods in case-control studies, little attention has been given to sparse and efficient modeling of GEI in longitudinal studies. In a two-way table for GEI with rows and columns as categorical variables, a conventional saturated interaction model involves estimation of a specific parameter for each cell, with constraints ensuring identifiability. The estimates are unbiased but are potentially inefficient because the number of parameters to be estimated can grow quickly with increasing categories of row/column factors. On the other hand, Tukey’s one degree of freedom (df) model for non-additivity treats the interaction term as a scaled product of row and column main effects. Due to the parsimonious form of interaction, the interaction estimate leads to enhanced efficiency and the corresponding test could lead to increased power. Unfortunately, Tukey’s model gives biased estimates and low power if the model is misspecified. When screening multiple GEIs where each genetic and environmental marker may exhibit a distinct interaction pattern, a robust estimator for interaction is important for GEI detection. We propose a shrinkage estimator for interaction effects that combines estimates from both Tukey’s and saturated interaction models and use the corresponding Wald test for testing interaction in a longitudinal setting. The proposed estimator is robust to misspecification of interaction structure. We illustrate the proposed methods using two longitudinal studies — the Normative Aging Study and the Multi-Ethnic Study of Atherosclerosis.
PMCID: PMC4227925  PMID: 25112650
adaptive shrinkage estimation; gene-environment interaction; longitudinal data; Tukey’s one df test for non-additivity
19.  Do Psychosocial Stress and Social Disadvantage Modify the Association Between Air Pollution and Blood Pressure? 
American Journal of Epidemiology  2013;178(10):1550-1562.
Researchers have theorized that social and psychosocial factors increase vulnerability to the deleterious health effects of environmental hazards. We used baseline examination data (2000–2002) from the Multi-Ethnic Study of Atherosclerosis. Participants were 45–84 years of age and free of clinical cardiovascular disease at enrollment (n = 6814). The modifying role of social and psychosocial factors on the association between exposure to air pollution comprising particulate matter less than 2.5 µm in aerodynamic diameter (PM2.5) and blood pressure measures were examined using linear regression models. There was no evidence of synergistic effects of higher PM2.5 and adverse social/psychosocial factors on blood pressure. In contrast, there was weak evidence of stronger associations of PM2.5 with blood pressure in higher socioeconomic status groups. For example, those in the 10th percentile of the income distribution (i.e., low income) showed no association between PM2.5 and diastolic blood pressure (b = −0.41 mmHg; 95% confidence interval: −1.40, 0.61), whereas those in the 90th percentile of the income distribution (i.e., high income) showed a 1.52-mmHg increase in diastolic blood pressure for each 10-µg/m3 increase in PM2.5 (95% confidence interval: 0.22, 2.83). Our results are not consistent with the hypothesis that there are stronger associations between PM2.5 exposures and blood pressure in persons of lower socioeconomic status or those with greater psychosocial adversity.
PMCID: PMC3888274  PMID: 24064742
air pollution; blood pressure; population groups; social environment; social medicine; social psychology
20.  Relationship between the cortisol awakening response and other features of the diurnal cortisol rhythm: The Multi-Ethnic Study of Atherosclerosis 
Psychoneuroendocrinology  2013;38(11):10.1016/j.psyneuen.2013.06.032.
Cumulative cortisol burden is known to influence neuropsychiatric and metabolic disorders. To better understand the relationship between daily cortisol exposure and measures of the diurnal circadian cortisol rhythm, we examined the cross-sectional association of the cortisol awakening response (CAR) with wake-up cortisol, bedtime cortisol, diurnal slope, and total cortisol area under the curve (AUC). Up to 18 salivary cortisol samples were collected over 3 days from 935 White, Hispanic, and Black individuals (mean age 65 ± 9.8 years) in the Multi-Ethnic Study of Atherosclerosis. Outcome measures included awakening cortisol, CAR (awakening to 30 min post-awakening), early decline (30 min to 2 h post-awakening), late decline (2 h post-awakening to bedtime), and the corresponding AUCs. Total cortisol AUC was a summary measure of cumulative cortisol exposure. Higher CAR was associated with significantly lower wake-up cortisol (β = −0.56; 95% CI: −0.59 to −0.53) and a higher early decline AUC (β = 0.38; 95% CI: 0.34–0.42) but was not associated with total cortisol AUC (β = 0.04; 95% CI: −0.01 to 0.09), or other diurnal cortisol curve components following multivariable adjustment. Total cortisol AUC was significantly and positively associated with wake-up cortisol (β = 0.36; 95% CI: 0.32–0.40), bedtime cortisol (β = 0.61; 95% CI: 0.58–0.64), and other AUC measures, following multivariable adjustment. Associations were similar by sex, race/ethnicity, and age categories. We conclude that bedtime cortisol showed the strongest correlation with total cortisol AUC, suggesting it may be a marker of daily cortisol exposure.
PMCID: PMC3812410  PMID: 23890985
Cortisol awakening response (CAR); Hypothalamic–pituitary–adrenal (HPA) axis; Diurnal cortisol; Correlation; Population-based study
21.  Discrete Land Uses and Transportation Walking in Two U.S. Cities: The Multi-Ethnic Study of Atherosclerosis 
Health & place  2013;24:10.1016/j.healthplace.2013.09.007.
This study examines associations of disaggregate land uses with self-reported walking for transportation among participants of the Multi-Ethnic Study of Atherosclerosis (MESA) in Forsyth County, NC and New York, NY. Network distance to each use (in miles), intensity (number of uses per ½-mile network buffer) of each use and diversity (number of different uses per ½-mile network buffer) of uses were calculated using Geographic Information Systems (GIS). Associations with odds of meeting recommended physical activity levels (150 min/week) were examined after controlling for individual- and census-tract-level covariates. Greater distance to and lower intensity of pedestrian-oriented uses, specifically those for social interactions, were associated with lower odds of meeting recommendations in NY. Results suggest that land uses linked to social interactions may be useful for encouraging increased transportation walking.
PMCID: PMC3851044  PMID: 24148201
Land use; Walking; Transportation; Geographic Information Systems (GIS)
22.  Associations between neighborhood characteristics and self-rated health: A cross-sectional investigation in the Multi-Ethnic Study of Atherosclerosis (MESA) cohort 
Health & place  2013;24:10.1016/j.healthplace.2013.10.001.
Quantifying the effects of specific neighborhood features on self-reported health is important to understanding the global health impact of neighborhood context. We investigated associations of neighborhood poverty, sociability and walkability with self-rated physical and mental health in the Multi-Ethnic Study of Atherosclerosis (MESA). In separate models, each neighborhood variable was associated with physical health but associations with sociability and walkability were stronger than those for poverty. Only walkability remained significant after adjusting for the other neighborhood variables. There was no evidence that self-rated mental health as assessed by the SF12 was associated with neighborhood poverty, walkability or sociability. This study provides information on how neighborhood context is associated with global health in diverse midlife and older persons.
PMCID: PMC3874143  PMID: 24211514
Neighborhood; self-rated health; income; education; employment
23.  Socioeconomic Position Is Positively Associated With Blood Pressure Dipping Among African-American Adults: The Jackson Heart Study 
American journal of hypertension  2011;24(9):1015-1021.
Blunted nocturnal blood pressure (NBP) dipping is a significant predictor of cardiovascular events. Lower socioeconomic position (SEP) may be an important predictor of NBP dipping, especially in African Americans (AA). However, the determinants of NBP dipping are not fully understood.
The cross-sectional associations of individual and neighborhood SEP with NBP dipping, assessed by 24-h ambulatory BP monitoring, were examined among 837 AA adults (Mean age: 59.2 ± 10.7 years; 69.2% women), after adjustment for age, sex, hypertension status, body mass index (BMI), health behaviors, office, and 24-h systolic BP (SBP).
The mean hourly SBP was consistently lower among participants in the highest category of individual income compared to those in the lowest category, and these differences were most pronounced during sleeping hours. The odds of NBP dipping (defined as >10% decline in the mean asleep SBP compared to the mean awake SBP) increased by 31% (95% confidence interval: 13–53%) and 18% (95% confidence interval: 0–39%) for each s.d. increase in income and years of education, respectively, after multivariable adjustment.
NBP dipping is patterned by income and education in AA adults even after accounting for known risk factors. These results suggest that low SEP is a risk factor for insufficient NBP dipping in AA.
PMCID: PMC4206938  PMID: 21654853
ambulatory blood pressure monitoring; blood pressure; hypertension; Jackson Heart Study; nocturnal dipping; socioeconomic position; systole
24.  Neighborhood socioeconomic characteristics and differences in the availability of healthy food stores and restaurants in Sao Paulo, Brazil 
Health & place  2013;23:39-47.
Differential access to healthy foods has been hypothesized to contribute to health disparities, but evidence from low and middle-income countries is still scarce. This study examines whether the access of healthy foods varies across store types and neighborhoods of different socioeconomic statuses (SES) in a large Brazilian city. A cross-sectional study was conducted in 2010–2011 across 52 census tracts. Healthy food access was measured by a comprehensive in-store data collection, summarized into two indexes developed for retail food stores (HFSI) and restaurants (HMRI). Descriptive analyses and multilevel models were used to examine associations of store type and neighborhood SES with healthy food access. Fast food restaurants were more likely to be located in low SES neighborhoods whereas supermarkets and full service restaurants were more likely to be found in higher SES neighborhoods. Multilevel analyses showed that both store type and neighborhood SES were independently associated with in-store food measures. We found differences in the availability of healthy food stores and restaurants in Sao Paulo city favoring middle and high SES neighborhoods.
PMCID: PMC3758426  PMID: 23747923
Neighborhood; Food environment; Socioeconomic factors; Disparities; Food stores
25.  Socioeconomic status, John Henrysim and blood pressure among African-Americans in the Jackson Heart Study 
John Henryism connotes a strong behavioral predisposition to engage in effortful, active coping with difficult social and economic stressors. This behavioral predisposition is measured by the 12 item John Henryism Scale for Active Coping (JHAC). The John Henry hypothesis predicts that the well-known inverse socioeconomic status (SES)-blood pressure association will be stronger among persons who score high rather than low on the JHAC. We tested this hypothesis in a large African American cohort using baseline data from the Jackson Heart Study. Unlike previous studies, we used multiple indicators of SES: income, education, occupation, childhood SES and cumulative SES. Because the hypothesis is most relevant for adults still in the labor force, we excluded retired participants, yielding a sample size of 3,978. Gender-specific Poisson regression models for hypertension adjusting for age, John Henryism, SES, and a John Henryism-SES interaction term, were fit to examine associations. Separate models were fit for each SES indicator. We found some evidence that John Henryism modified the association between income and hypertension in men: low income was associated with higher prevalence of hypertension in men who scored high on John Henryism (prevalence ratio (PR) for low vs. high income tertile 1.12), but with lower hypertension prevalence among men who scored low on John Henryism (PR 0.85, one sided P value for multiplicative interaction <0.05). For women, the association of low income with higher hypertension prevalence was stronger at lower than higher levels of John Henryism (PR 1.27 and 1.06 at low and high levels of John Henryism respectively, P value<0.05). There was no evidence that John Henryism modified the associations of hypertension with other SES indicators in men or women. The modest support of the John Henryism Hypothesis in men only, adds to the literature on this subject, but underscores questions regarding the gender, spatial, socioeconomic and historical contexts in which the hypothesis is valid.
PMCID: PMC4149751  PMID: 23906131
United States; John Henryism; socioeconomic status; hypertension; African American

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