DOI: 10.1161/CIRCULATIONAHA.114.011345
Neighborhood-Level Racial/Ethnic Residential Segregation and Incident Cardiovascular Disease: The Multi-Ethnic Study of Atherosclerosis
Running title: Kershaw et al.; Residential segregation and cardiovascular disease Kiarri N. Kershaw, PhD1; Theresa L. Osypuk, PhD2; D. Phuong Do, PhD3; Peter J. De Chavez, MS1; Ana V. Diez Roux, MD PhD4
1
Dept of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago,
IL; IL L; 2Di Division Divi visi vi sion si on off Epidemiology Ep & Community H Health, eallth, University ea y of Min M Minnesota innesota nn School of Public Hea H ealth, Minneapolis, Minnnea eapo polis, po s, MN; MN; 3De Depts Dept ptss of of Public Publi licc Health Heallth Policy Poolic oliccy & Ad Admi Administration, mini mi nist straation st on n, an andd Ep Epid Epidemiology, idem id mio iolo lo ogy, Health, University Univ Un iv ver ersiity ooff W Wisconsin-Milwaukee, isscon sconnsiinn-Mi Milw Mi wau auke kee, ke e, M Milwaukee, ilw il wauukee ukeee, WI WI; 4De Deptt ooff Ep Epidemiology pid i em mio iolo logy lo gy aand nd B Biostatistics, io ostat atis isstiics cs, Drexel Drex Dr exel el University Uni nive vers rsit ityy School Scho Sc cho hool ol of of Public Pub ubli licc He Health, eal alth th, Ph Phil Philadelphia, ilad adel delpphia phia,, PA
Address for Correspondence: Kiarri N. Kershaw, PhD Northwestern University 680 N Lake Shore Drive, Suite 1400 Chicago, IL 60611 Tel: 312-503-4014 Fax: 312-908-9588 E-mail: [email protected]
Journal Subject Code: Etiology:[8] Epidemiology 1 Downloaded from http://circ.ahajournals.org/ at BIBLIOTHEQUE DE L'UNIV LAVAL on December 2, 2014
DOI: 10.1161/CIRCULATIONAHA.114.011345
Abstract Background—Previous research suggests neighborhood-level racial/ethnic residential segregation is linked to health, but it has not been studied prospectively in relation to cardiovascular disease (CVD). Methods and Results—Participants were 1,595 non-Hispanic Black, 2,345 non-Hispanic White, and 1,289 Hispanic adults from the Multi-Ethnic Study of Atherosclerosis free of CVD at baseline (ages 45-84). Own-group racial/ethnic residential segregation was assessed using the Gi* statistic, a measure of how the neighborhood racial/ethnic composition deviates from surrounding counties’ racial/ethnic composition. Multivariable Cox proportional hazards modeling was used to estimate hazard ratios (HR) for incident CVD (first definite angina, probable angina followed by revascularization, myocardial infarction, resuscitated cardiac arrest, CHD death, stroke, or stroke death) over 10.2 median years of follow-up. Among ngg B lack la cks, ck s, eeach achh ac Blacks, tandard deviation increase in Black segregation was associatedd with a 12% high gher err hhazard azar az ardd of ar standard higher developing CVD after adjusting for demographics (95% Confidence Interval (CI): 1.02, 1.22). Th his association assoc ssoccia iati tion ti n ppersisted er ersisted after adjustment for nneighborhood-level eighborhood-leveel char eig arrac acteristics, individual This characteristics, ociioe o conomi miic position, positi pos tiion, on, and and CVD CVD risk r sk factors ri faccto torss (HR: (HR: 1.12; 1.1 .1 12; 95% 95% 5 CI: CI:: 1.02, 1.0 02, 2, 1.23). 1.2 23) 3).. For For Whites, Whit Wh ites it es,, es socioeconomic high hi ghher e White te segregation seg greegattion was was associated asssoci ciat ci ated ed d with wiith lower low wer CVD wer CV VD risk risk after affteer adjusting ad dju just stiing for fo demographics demo demo moggraph hiccs higher HR: 00.88; .8 88; 995% 5% %C I: 00.81, .8 .81, 81, 1 00.96), .9 96) 6),, bu butt no nott af afte terr fu te furt rtthe herr ad dju just stme st ment me nt ffor or nneighborhood eigh ei ghbo gh b rh bo rhoo oodd ch oo char arac ar acte ac teri te rist ri stic st icss ic (HR: CI: after further adjustment characteristics. Segregation was was no nott as asso s ciiat so ated e with ed w th wi hC VD rrisk iskk am is amon ongg Hi on Hisp span sp anic an ics. ic s Si s. Simi mila mi larr re la resu suult ltss we were r obtained re associated CVD among Hispanics. Similar results after adjusting for time-varying segregation and covariates. Conclusions—The association of residential segregation with cardiovascular risk varies according to race/ethnicity. Further work is needed to better characterize the individual- and neighborhood-level pathways linking segregation to CVD risk.
Key words: epidemiology, cardiovascular events, race and ethnicity, neighborhoods
2 Downloaded from http://circ.ahajournals.org/ at BIBLIOTHEQUE DE L'UNIV LAVAL on December 2, 2014
DOI: 10.1161/CIRCULATIONAHA.114.011345
Introduction The spatial distribution of racial/ethnic groups in U.S. metropolitan areas is highly patterned as a consequence of a complex set of social, cultural, and economic forces that also lead to the differential distribution of and exposure to resources and opportunities across space by race/ethnicity.1, 2 Despite discrimination and other exclusionary housing practices having been outlawed for over 50 years, racial/ethnic residential segregation in U.S. metropolitan areas remains high; the average White individual lives in a neighborhood that is 75% White while the average Black and Hispanic individuals, who make up approximately 13 and 16% of the U.S. population, respectively,3 live in neighborhoods that are only 35% White.4 Predominantly minority neighborhoods are disproportionately higher in poverty t than predomina predominantly antly ntly White Whi hite te neighborhoods.5 It has been proposed that racial/ethnic residential segregation may lead to ad dve vers rsse cardiovascular caard rdio iovaasc scul u ar (CVD) outcomes for mino noriities through mu no m ltip iple le m echanisms, including adverse minorities multiple mechanisms, limiting imiiti t ng opportunities opporrtu tuni n ties ni es for foor or socioeconomic soc ocio ioec io econ onom on om micc mobility, mob obilityy, access ob acccesss to to hhealth-promoting eaalt lthh-pr h-prom omot om otin ingg re in res resources, souurce urces, s,, ex exposure xpo posu sure su re to to safe safe areas, arreas reas, and and access accceess to to quality quual alit ityy health it heal he a th al th care. carre.2, 6 H However, o ev ow ver er,, aass tthe he eethnic thni th nicc ddensity ennsitty hypothesis pposits, osit os itts, ssegregation egre eg rega re gati tion ti on m a aalso ay l o co ls conf nfer nf er be ene n fi f ci cial al hhealth ealt ea lthh ou lt outc tcom tc omes om es ffor or m inor in orit or i ies by it may confer beneficial outcomes minorities fostering strong social networks, reinforcing social control, and shielding minorities from exposure to prejudice and discrimination.7 While studies examining associations of metropolitan-level segregation with mortality have largely found that higher metropolitan area segregation is associated with worse outcomes among Blacks,8-12 findings from studies investigating the relationship between segregation and mortality across neighborhoods within cities (herein referred to as neighborhood-level segregation) are less clear.13-19 Existing studies of neighborhood-level segregation and cardiovascular outcomes have largely used death certificate data to examine associations of
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DOI: 10.1161/CIRCULATIONAHA.114.011345
racial composition with CVD mortality rates, and findings generally indicate higher segregation is related to lower mortality particularly among older Blacks.13-15 However, these studies are limited by their inability to capture non-fatal cardiovascular outcomes and minimal adjustment for individual-level confounders. Moreover, studies of segregation and health have largely focused on Blacks.20 Few have examined the impact of segregation on health for other minority groups, and none to our knowledge have examined associations of segregation with cardiovascular outcomes. Given that the Hispanic population is projected to double, to comprise almost one-third of the U.S. population by 2060,21 there is a strong imperative to also investigate the impact of residential segregation egregation in Hispanics. Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), we prospectively examined ex xam amin ined in ed associations ass ssocia iaati tion o s of own-group neighborhood-level neighborhoo oodd-level racial/ethnic oo racial/eethn h icc residential residential es segregation with cardiovascular Black, White, and Hispanic w ith h incident ca car rdiova vaasccul ular lar ddisease ise seaase ase in n nnon-Hispanic on--Hispaanic Blac B lackk, nnon-Hispanic on n-H Hispaanic Hisp anic W hite, an hite nd Hi ispa spani a ni c adults. ad dul u ts ts.. We then the h n assessed assess asse sssed d whether wheeth her these the h see relationships rela re lattion la onsh on shhip ps were were explained expl p aiineed by iindividual nddiv ivid idua id uaal socioeconomic position neighborhood traditional individual ocioeconomi miic po posi siti si t on ((SEP), ti SE EP) P , ne neig ig ghb h or orho hood ho od ccharacteristics, hara ha ract ra c er ct eris isti is tiics cs,, an andd tr rad adit itio it iona io nall in na ndi divi vidu vi dual du a behavioral and biological CVD risk factors. ‘
Methods Study population MESA is an observational prospective cohort study designed to examine the determinants of subclinical cardiovascular disease in adults aged 45-84 years. Self-identified Black, Chinese, Hispanic, and White participants free of clinical cardiovascular disease at baseline were recruited from six sites (New York, New York; Baltimore City and County, Maryland; Forsyth County,
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DOI: 10.1161/CIRCULATIONAHA.114.011345
North Carolina; St. Paul, Minnesota; Chicago, Illinois; and Los Angeles County, California) between 2000 and 2002. Random population samples were selected at each site using various population-based approaches. Additional details are provided elsewhere.22 Of the selected persons deemed eligible after screening, 59.8% participated in the study. Institutional review board approval was obtained at each site and all participants gave informed consent. Four additional examinations have been completed since baseline: exam 2 (2002-2004), exam 3 (2004-2005), exam 4 (2005-2007) and exam 5 (2010-2012). Due to the small number of cardiovascular events among Chinese participants, our analyses were restricted to Blacks, Hispanics, and Whites. Racial/ethnic residential segregation Neighborhood-level racial/ethnic residential segregation was measured separately for Blacks, 23 Whites, Wh hit ites es,, an es and nd Hispanics Hisp sppan anic i s using the local Gi* statist statistic, tic ic,23 based on thee geocoded g occod ge oded e addresses of MESA
participants part tic i ipants linked lin nke kedd too U.S. U.S S. Census Cennsus Ce nsuss data. dat ataa. The Thee Gi* sta statistic tattisttic returns retturrns a Z-score Z-sccor oree for fo or each each neighborhood neiigh ghbo borh r ood rh (census cen ensu suus tr trac tract), act) ac t),, in t) indi indicating diica cati tiing g tthe he eextent xteent tto xt o wh whic which ichh th ic the he racial/ethnic raccial ra ciall/eeth thni nicc co ccomposition mpos mp o ittio os on in n tthe h ffocal he ocall tra oc tract raact aand nd nd neighboringg tr tracts rac acts tss ddeviates evia ev iaatess fr from om tthe hee m mean e n rracial ea acia ac iaal co comp composition m os mp osit itio it ionn of ssome io om me la larg larger rger rg e aareal er real re al uunit nt ni surrounding the tract (in our case the set of counties represented in each MESA site). Higher positive Gi* Z-scores indicate higher racial/ethnic segregation or clustering (over-representation), scores near 0 indicate racial integration, and lower negative scores suggest lower racial/ethnic representation (under-representation), compared to the racial composition of the larger areal unit. Most studies of neighborhood-level racial/ethnic residential segregation use racial/ethnic composition, or the proportion of a race/ethnic group in a neighborhood, as a proxy for segregation.24 However, this measure is limited in that it does not incorporate any information on the racial composition of the larger area in which the neighborhood is embedded or on the
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DOI: 10.1161/CIRCULATIONAHA.114.011345
distribution of groups in space.1 The Gi* statistic, in contrast, better reflects both the contextual and spatial aspects of segregation. A given neighborhood will have a higher Gi* statistic the larger the difference between its racial composition and the composition of the larger areal unit. In addition, a neighborhood surrounded by similarly segregated areas will have a higher Gi* statistic than those surrounded by less segregated areas. Further details on the Gi* statistic are available in the Supplemental Methods. Fatal and nonfatal incident CVD Incident CVD was defined as first definite angina, probable angina followed by revascularization, myocardial infarction, resuscitated cardiac arrest, coronary heart disease CHD) death, stroke, or stroke death. Incident CHD, defined as first myocardiall in infa farccti fa tion on,, on (CHD) infarction, esuscitated cardiac arrest, or CHD death, was also assessed as a secondary outcome. MESA resuscitated us sess a sstandard tand tand ndar arrd ad adj ju judication protocol to classifyy ev eevents. ents.22 Every 99-12 - 2 mo -1 mont months, n hs, participants (or uses adjudication when w heen en necessary ry ttheir heir pproxies) ro oxi xies ies es)) ar aree co contacted onttacctedd to o inqu inquire quiire ab qu about bouut ho hos hospital spiital aadmissions, dm mis issi sioons, ons, ccardiovascular ardi ardi diov vas ascu cullar cu diagnoses, Possible vascular are abstracted hospital records and sent diag di agno ag nose no ses, s, aand nd ddeaths. nd eaath thss. P ossiibl os b e va vasc scul sc ular ar eevents vent ve ntts ar re ab bst stra ract ra cted ct d ffrom ro om ho hosp spit itaal re eco c rd rdss an nd se sen nt ffor nt o or review eview and cclassification laasssiffic icat a io at i n by aan n iindependent n ep nd epen nde dent nt aadjudication djud dj uddic i at a io on co comm committee. mmit mm itteee. it e O Outcome utco ut come co me ffollow-up ollo ol lowlo w up data were available for events occurring on or before and adjudicated through December 31, 2011 (median follow-up of 10.2 years). Covariates Sociodemographic covariates included age, sex, education (categorized as less than high school graduate, high school graduate, some college, and college degree or higher), health insurance status, and income (specified in quartiles). Baseline income was available and used for 80.0% of Black participants, 85.0% of Hispanic participants, and 88.3% of White participants. When baseline income was missing, data from Exam 2 were used (4.4% of Black participants, 1.2% of
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DOI: 10.1161/CIRCULATIONAHA.114.011345
Hispanic participants, and 1.2% of White participants). Neighborhood (census tract) characteristics were adjusted for included neighborhood poverty, the neighborhood social environment, and the neighborhood physical environment. Neighborhood poverty was defined as the percent of neighborhood residents who were below the U.S. Census Bureau-defined poverty threshold, based on baseline address linked to Census 2000 data.25 Survey-based information on the neighborhood social and physical environments was collected as part of the MESA Neighborhood study, an ancillary study designed to assess neighborhood conditions of potential relevance to cardiovascular disease. In addition to MESA participants, a sample of 5,988 individuals (recruited between January and August 2004) residing n the same neighborhoods as MESA participants were asked to rate several aspe ectss off th ects thei eirr ei in aspects their neighborhood via a telephone survey. Supplementing the neighborhood survey with participants ot theer th than an n tthose hosee iin ho n ME M SA reduced the potentiall ffor or same source bbias, i s,, iincreased ia ncre nc r ased the withinother MESA nneighborhood eig ghb h orhoodd sample sam ampl plee size siize for for or constructing connst strruc ructiing more mo reliable reliab rel blee subjective sub ubje j cttiv je ive neighborhood neig ne ighb hboorh orhood hood d vvariables, a ia ar i bl bles es,, and an prov pr ovid ov ided id e am ed oree re or epr p eseenta entatiive v me meas asur urre of nneighborhood eiigh ghbo borrhoo bo oodd cond oo cconditions. ond ndit itio i ns io ns..26 provided more representative measure The ne eig ighb hbbor o ho h od o social soc ociaal environment e vi en v ro onm nmen entt me en meas asur as u e wa ur wass ge gene nera ne r te tedd by ssumming u mi um ming ng 3 sscales, cales, neighborhood measure generated including neighborhood safety (a composite of three self-reported questions of safety and violence), neighborhood social cohesion (a composite of five self-reported questions on feelings of mutual trust and solidarity with neighbors), and aesthetic quality (a composite of three selfreported questions relating to noise, presence of trash and litter, and overall neighborhood attractiveness). Possible scores ranged from 3 to 15, with higher scores indicating a better social environment (Cronbach’s alpha: 0.89). The neighborhood physical environment measure was constructed by summing responses of neighborhood walking environment (4 items) and neighborhood food environment (2 items) scales. Possible scores ranged from 2 to 10
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DOI: 10.1161/CIRCULATIONAHA.114.011345
(Cronbach’s alpha: 0.75). For each neighborhood scale, conditional empirical Bayes estimates were derived to increase reliability of the measures. Additional details on the development of the scales are provided elsewhere.26 Both the neighborhood social and physical environment measures were categorized into tertiles. We also adjusted for traditional behavioral and biological CVD risk factors, including cigarette smoking, physical activity, diabetes, systolic blood pressure, total cholesterol, HDL cholesterol, and BMI. Physical activity was categorized as high (1000 MET-minutes per week of energy expenditure from recreational activity), intermediate (>0 and < 1000 MET-minutes per week), or physically inactive based on the 2008 Physical Activity Guidelines for Americans.27 Cigarette smoking was categorized as current, former, and never; alcohol use wa was as ca cate categorized ego gori rize ri zedd as ze heavy (>14 drinks per week for men and >7 drinks per week for women), moderate, or none. Diabetes Diab Di abet ab etees et es was was a defined def effin ined e as having a fasting glucose see 126 mg/dl or be bbeing in ng on on insulin or oral hypoglycemic medications hypoglycemic hyp po cm ed diccat atio onss 288. Re Res Resting stin stin ingg seated seeateed blood blood od pre pressure essur ssurre wa wass meas m measured easur ured ed tthree hree hr ee ttimes im mess aatt a si ssingle ngle visit visi vi sitt by trained si tra rain ined in ed and andd certified certi ertiifi fied ed clinic clin inic ic staff sta tafff ff using usi sinng ng a Dinamap Din nam map p PRO PRO O 100 100 0 aautomated uttom matted ooscillometric sccilllom metr metr t ic device (Critikon, (Critik ik kon on,, Ta Tamp Tampa, mpa, mp a F a, FL), L),, aand L) nd tthe h aaverage he veeraage ooff th thee la last st tw twoo me meas measurements sur urem emen em ents en t w ts was as uused. sed. se d 29 Plasmaa HDL and total cholesterol were measured by the cholesterol-oxidase method. 30 Statistical analysis All analyses were stratified by race/ethnicity. Descriptive analyses compared baseline participant characteristics by levels of residential segregation score (high: Gi* >1.96; medium: Gi* 0 – 1.96; and low: Gi* < 0). The high category corresponds to statistically significant clustering at the Į=0.05 level, and the low category corresponds to both the absence of any clustering or areas in which the group is significantly under-represented (Gi* < -1.96). These categories were combined because the number of Blacks and Hispanics living in areas where they were
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DOI: 10.1161/CIRCULATIONAHA.114.011345
significantly under-represented was very small. Baseline characteristics were also compared in those who did and did not develop incident CVD/CHD. A series of marginal Cox proportional hazards regression modeling were estimated using a robust sandwich estimator to examine the relationship between baseline continuous segregation and CVD/CHD event while accounting for any residual correlations among individuals residing in the same census tract.31, 32 Time was measured from date of the baseline exam and subjects were censored at the last contact date for outcome information if a CVD/CHD event was not observed. The proportional hazards assumption was tested by evaluating interactions of analysis time with the full complement of covariates; there was no evidence of violation. Model 1 adjusted for demographics including age, sex, and MESA study site (nativity was waas adjusted ad dju ust sted ed for for o as well for the analysis of Hispanics). We did not find evidence suggesting associations of egr greg egat eg atio at ionn wi io w th h iincident nc ncident CVD varied by MESA A st stu udy site (P forr in iinteraction teera racction ct 0.5), so findings segregation with study ar re pr ppresented esented po pool oled ed d aacross crrosss th thee si site t s. te s. M odell 2 add dittionnally ad djussteed fo djus fforr neig nneighborhood-level eig ghb hbor orho hood ho od-l od - ev -l vel are pooled sites. Model additionally adjusted ch har arac acte ac t ri te rist stic st icss through ic th hro oug gh which wh h segregation seegr greg egat eg attio ionn may mayy impact impa im paactt CVD/CHD, CVD VD/C CHD HD,, including incl in clluddin ingg neighborhood neig ne ighb ig hborrho hb hood od characteristics poverty, the neighborhood nei eigh ghbo gh borh bo rh hoo o d physical phys ph yssic ical al environment, envvir iron onme on ment me n , and nt and the th he neighborhood neig ne ighb ig hbor hb orho hood ho od social soc ocia iall environment. envi en viro vi ronm ro n ent. Thee Black (r=0.31), Hispanic (r=0.31), and White (r=-0.59) segregation scores were correlated with neighborhood poverty, but not strongly enough to preclude us from assessing their independent associations. Model 3 further adjusted for individual factors that may have been influenced by segregation: education and income. Model 4 additionally adjusted for baseline CVD risk factors including hypercholesterolemia, hypertension, diabetes, body mass index, physical activity, current alcohol use, and current cigarette smoking as potential individual-level mediators. We estimated three additional models to leverage our longitudinal data structure and more precisely operationalize our constructs. We first modeled the behavioral and biological
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DOI: 10.1161/CIRCULATIONAHA.114.011345
CVD risk factors as time-varying covariates (Model 5), and then we specified both residential segregation and CVD risk factors as time-varying (Model 6). As a secondary analysis, we also examined associations of change in segregation score with incident CVD. This was done by calculating the difference in the segregation score between each exam and baseline and including this variable as a time varying covariate in the Cox regression. For analyses of Hispanic segregation, we also tested whether the association between segregation and incident CVD varied between those of Mexican origin and those not of Mexican origin (including Dominican, Puerto Rican, Cuban, and other Hispanics) by incorporating a segregation*Mexican origin interaction term. This was motivated by prior research that has Hispanic subgroup. found associations between residential environment and health to differ by Hisp pan anic icc sub ubgr ub grou gr oupp.33, ou 34 4
Small sample sizes precluded assessing this relationship separately in the other Hispanic
ubg bgro ro oups. ups. Based Based ed d on on previous research,35 we also so te tested ested for effect ctt mod modification oddif ific ication by nativity and subgroups. acculturation. ac ccu ulturation. Nativity Nativit ityy was was dichotomized dich di chot ottom omizzed ass fo foreign-born oreiggn-boorn rn vvs. s. U US-born. S-bborn born.. Acculturation Accu Accu ulttur urat atio at io on wa wass assessed summary score length lived US born; as sse sess sssed e uusing sing si ng a su umma umma mary r sco ry co oree bbased ased as ed d oon n le leng nggth ooff ttime im me li liv vedd in n the he U S (3 ((3=US =US =U S bo orn rn;; 2=fo 22=foreign =fore reeig gn born and lived ed d iin n th thee US 20 20 yyears; ears ea r ; 1= rs 1=fo 1=foreign-born f re fo reig ignig n bo nborn rnn aand ndd llived ive vedd in tthe hee U US S 10 10-1 10-19 -199 ye year years; ars; ar s; aand nd 0=foreign born and lived in the US
Neighborhood-Level Racial/Ethnic Residential Segregation and Incident Cardiovascular Disease: The Multi-Ethnic Study of Atherosclerosis
Running title: Kershaw et al.; Residential segregation and cardiovascular disease Kiarri N. Kershaw, PhD1; Theresa L. Osypuk, PhD2; D. Phuong Do, PhD3; Peter J. De Chavez, MS1; Ana V. Diez Roux, MD PhD4
1
Dept of Preventive Medicine, Northwestern University Feinberg School of Medicine, Chicago,
IL; IL L; 2Di Division Divi visi vi sion si on off Epidemiology Ep & Community H Health, eallth, University ea y of Min M Minnesota innesota nn School of Public Hea H ealth, Minneapolis, Minnnea eapo polis, po s, MN; MN; 3De Depts Dept ptss of of Public Publi licc Health Heallth Policy Poolic oliccy & Ad Admi Administration, mini mi nist straation st on n, an andd Ep Epid Epidemiology, idem id mio iolo lo ogy, Health, University Univ Un iv ver ersiity ooff W Wisconsin-Milwaukee, isscon sconnsiinn-Mi Milw Mi wau auke kee, ke e, M Milwaukee, ilw il wauukee ukeee, WI WI; 4De Deptt ooff Ep Epidemiology pid i em mio iolo logy lo gy aand nd B Biostatistics, io ostat atis isstiics cs, Drexel Drex Dr exel el University Uni nive vers rsit ityy School Scho Sc cho hool ol of of Public Pub ubli licc He Health, eal alth th, Ph Phil Philadelphia, ilad adel delpphia phia,, PA
Address for Correspondence: Kiarri N. Kershaw, PhD Northwestern University 680 N Lake Shore Drive, Suite 1400 Chicago, IL 60611 Tel: 312-503-4014 Fax: 312-908-9588 E-mail: [email protected]
Journal Subject Code: Etiology:[8] Epidemiology 1 Downloaded from http://circ.ahajournals.org/ at BIBLIOTHEQUE DE L'UNIV LAVAL on December 2, 2014
DOI: 10.1161/CIRCULATIONAHA.114.011345
Abstract Background—Previous research suggests neighborhood-level racial/ethnic residential segregation is linked to health, but it has not been studied prospectively in relation to cardiovascular disease (CVD). Methods and Results—Participants were 1,595 non-Hispanic Black, 2,345 non-Hispanic White, and 1,289 Hispanic adults from the Multi-Ethnic Study of Atherosclerosis free of CVD at baseline (ages 45-84). Own-group racial/ethnic residential segregation was assessed using the Gi* statistic, a measure of how the neighborhood racial/ethnic composition deviates from surrounding counties’ racial/ethnic composition. Multivariable Cox proportional hazards modeling was used to estimate hazard ratios (HR) for incident CVD (first definite angina, probable angina followed by revascularization, myocardial infarction, resuscitated cardiac arrest, CHD death, stroke, or stroke death) over 10.2 median years of follow-up. Among ngg B lack la cks, ck s, eeach achh ac Blacks, tandard deviation increase in Black segregation was associatedd with a 12% high gher err hhazard azar az ardd of ar standard higher developing CVD after adjusting for demographics (95% Confidence Interval (CI): 1.02, 1.22). Th his association assoc ssoccia iati tion ti n ppersisted er ersisted after adjustment for nneighborhood-level eighborhood-leveel char eig arrac acteristics, individual This characteristics, ociioe o conomi miic position, positi pos tiion, on, and and CVD CVD risk r sk factors ri faccto torss (HR: (HR: 1.12; 1.1 .1 12; 95% 95% 5 CI: CI:: 1.02, 1.0 02, 2, 1.23). 1.2 23) 3).. For For Whites, Whit Wh ites it es,, es socioeconomic high hi ghher e White te segregation seg greegattion was was associated asssoci ciat ci ated ed d with wiith lower low wer CVD wer CV VD risk risk after affteer adjusting ad dju just stiing for fo demographics demo demo moggraph hiccs higher HR: 00.88; .8 88; 995% 5% %C I: 00.81, .8 .81, 81, 1 00.96), .9 96) 6),, bu butt no nott af afte terr fu te furt rtthe herr ad dju just stme st ment me nt ffor or nneighborhood eigh ei ghbo gh b rh bo rhoo oodd ch oo char arac ar acte ac teri te rist ri stic st icss ic (HR: CI: after further adjustment characteristics. Segregation was was no nott as asso s ciiat so ated e with ed w th wi hC VD rrisk iskk am is amon ongg Hi on Hisp span sp anic an ics. ic s Si s. Simi mila mi larr re la resu suult ltss we were r obtained re associated CVD among Hispanics. Similar results after adjusting for time-varying segregation and covariates. Conclusions—The association of residential segregation with cardiovascular risk varies according to race/ethnicity. Further work is needed to better characterize the individual- and neighborhood-level pathways linking segregation to CVD risk.
Key words: epidemiology, cardiovascular events, race and ethnicity, neighborhoods
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DOI: 10.1161/CIRCULATIONAHA.114.011345
Introduction The spatial distribution of racial/ethnic groups in U.S. metropolitan areas is highly patterned as a consequence of a complex set of social, cultural, and economic forces that also lead to the differential distribution of and exposure to resources and opportunities across space by race/ethnicity.1, 2 Despite discrimination and other exclusionary housing practices having been outlawed for over 50 years, racial/ethnic residential segregation in U.S. metropolitan areas remains high; the average White individual lives in a neighborhood that is 75% White while the average Black and Hispanic individuals, who make up approximately 13 and 16% of the U.S. population, respectively,3 live in neighborhoods that are only 35% White.4 Predominantly minority neighborhoods are disproportionately higher in poverty t than predomina predominantly antly ntly White Whi hite te neighborhoods.5 It has been proposed that racial/ethnic residential segregation may lead to ad dve vers rsse cardiovascular caard rdio iovaasc scul u ar (CVD) outcomes for mino noriities through mu no m ltip iple le m echanisms, including adverse minorities multiple mechanisms, limiting imiiti t ng opportunities opporrtu tuni n ties ni es for foor or socioeconomic soc ocio ioec io econ onom on om micc mobility, mob obilityy, access ob acccesss to to hhealth-promoting eaalt lthh-pr h-prom omot om otin ingg re in res resources, souurce urces, s,, ex exposure xpo posu sure su re to to safe safe areas, arreas reas, and and access accceess to to quality quual alit ityy health it heal he a th al th care. carre.2, 6 H However, o ev ow ver er,, aass tthe he eethnic thni th nicc ddensity ennsitty hypothesis pposits, osit os itts, ssegregation egre eg rega re gati tion ti on m a aalso ay l o co ls conf nfer nf er be ene n fi f ci cial al hhealth ealt ea lthh ou lt outc tcom tc omes om es ffor or m inor in orit or i ies by it may confer beneficial outcomes minorities fostering strong social networks, reinforcing social control, and shielding minorities from exposure to prejudice and discrimination.7 While studies examining associations of metropolitan-level segregation with mortality have largely found that higher metropolitan area segregation is associated with worse outcomes among Blacks,8-12 findings from studies investigating the relationship between segregation and mortality across neighborhoods within cities (herein referred to as neighborhood-level segregation) are less clear.13-19 Existing studies of neighborhood-level segregation and cardiovascular outcomes have largely used death certificate data to examine associations of
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DOI: 10.1161/CIRCULATIONAHA.114.011345
racial composition with CVD mortality rates, and findings generally indicate higher segregation is related to lower mortality particularly among older Blacks.13-15 However, these studies are limited by their inability to capture non-fatal cardiovascular outcomes and minimal adjustment for individual-level confounders. Moreover, studies of segregation and health have largely focused on Blacks.20 Few have examined the impact of segregation on health for other minority groups, and none to our knowledge have examined associations of segregation with cardiovascular outcomes. Given that the Hispanic population is projected to double, to comprise almost one-third of the U.S. population by 2060,21 there is a strong imperative to also investigate the impact of residential segregation egregation in Hispanics. Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), we prospectively examined ex xam amin ined in ed associations ass ssocia iaati tion o s of own-group neighborhood-level neighborhoo oodd-level racial/ethnic oo racial/eethn h icc residential residential es segregation with cardiovascular Black, White, and Hispanic w ith h incident ca car rdiova vaasccul ular lar ddisease ise seaase ase in n nnon-Hispanic on--Hispaanic Blac B lackk, nnon-Hispanic on n-H Hispaanic Hisp anic W hite, an hite nd Hi ispa spani a ni c adults. ad dul u ts ts.. We then the h n assessed assess asse sssed d whether wheeth her these the h see relationships rela re lattion la onsh on shhip ps were were explained expl p aiineed by iindividual nddiv ivid idua id uaal socioeconomic position neighborhood traditional individual ocioeconomi miic po posi siti si t on ((SEP), ti SE EP) P , ne neig ig ghb h or orho hood ho od ccharacteristics, hara ha ract ra c er ct eris isti is tiics cs,, an andd tr rad adit itio it iona io nall in na ndi divi vidu vi dual du a behavioral and biological CVD risk factors. ‘
Methods Study population MESA is an observational prospective cohort study designed to examine the determinants of subclinical cardiovascular disease in adults aged 45-84 years. Self-identified Black, Chinese, Hispanic, and White participants free of clinical cardiovascular disease at baseline were recruited from six sites (New York, New York; Baltimore City and County, Maryland; Forsyth County,
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DOI: 10.1161/CIRCULATIONAHA.114.011345
North Carolina; St. Paul, Minnesota; Chicago, Illinois; and Los Angeles County, California) between 2000 and 2002. Random population samples were selected at each site using various population-based approaches. Additional details are provided elsewhere.22 Of the selected persons deemed eligible after screening, 59.8% participated in the study. Institutional review board approval was obtained at each site and all participants gave informed consent. Four additional examinations have been completed since baseline: exam 2 (2002-2004), exam 3 (2004-2005), exam 4 (2005-2007) and exam 5 (2010-2012). Due to the small number of cardiovascular events among Chinese participants, our analyses were restricted to Blacks, Hispanics, and Whites. Racial/ethnic residential segregation Neighborhood-level racial/ethnic residential segregation was measured separately for Blacks, 23 Whites, Wh hit ites es,, an es and nd Hispanics Hisp sppan anic i s using the local Gi* statist statistic, tic ic,23 based on thee geocoded g occod ge oded e addresses of MESA
participants part tic i ipants linked lin nke kedd too U.S. U.S S. Census Cennsus Ce nsuss data. dat ataa. The Thee Gi* sta statistic tattisttic returns retturrns a Z-score Z-sccor oree for fo or each each neighborhood neiigh ghbo borh r ood rh (census cen ensu suus tr trac tract), act) ac t),, in t) indi indicating diica cati tiing g tthe he eextent xteent tto xt o wh whic which ichh th ic the he racial/ethnic raccial ra ciall/eeth thni nicc co ccomposition mpos mp o ittio os on in n tthe h ffocal he ocall tra oc tract raact aand nd nd neighboringg tr tracts rac acts tss ddeviates evia ev iaatess fr from om tthe hee m mean e n rracial ea acia ac iaal co comp composition m os mp osit itio it ionn of ssome io om me la larg larger rger rg e aareal er real re al uunit nt ni surrounding the tract (in our case the set of counties represented in each MESA site). Higher positive Gi* Z-scores indicate higher racial/ethnic segregation or clustering (over-representation), scores near 0 indicate racial integration, and lower negative scores suggest lower racial/ethnic representation (under-representation), compared to the racial composition of the larger areal unit. Most studies of neighborhood-level racial/ethnic residential segregation use racial/ethnic composition, or the proportion of a race/ethnic group in a neighborhood, as a proxy for segregation.24 However, this measure is limited in that it does not incorporate any information on the racial composition of the larger area in which the neighborhood is embedded or on the
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DOI: 10.1161/CIRCULATIONAHA.114.011345
distribution of groups in space.1 The Gi* statistic, in contrast, better reflects both the contextual and spatial aspects of segregation. A given neighborhood will have a higher Gi* statistic the larger the difference between its racial composition and the composition of the larger areal unit. In addition, a neighborhood surrounded by similarly segregated areas will have a higher Gi* statistic than those surrounded by less segregated areas. Further details on the Gi* statistic are available in the Supplemental Methods. Fatal and nonfatal incident CVD Incident CVD was defined as first definite angina, probable angina followed by revascularization, myocardial infarction, resuscitated cardiac arrest, coronary heart disease CHD) death, stroke, or stroke death. Incident CHD, defined as first myocardiall in infa farccti fa tion on,, on (CHD) infarction, esuscitated cardiac arrest, or CHD death, was also assessed as a secondary outcome. MESA resuscitated us sess a sstandard tand tand ndar arrd ad adj ju judication protocol to classifyy ev eevents. ents.22 Every 99-12 - 2 mo -1 mont months, n hs, participants (or uses adjudication when w heen en necessary ry ttheir heir pproxies) ro oxi xies ies es)) ar aree co contacted onttacctedd to o inqu inquire quiire ab qu about bouut ho hos hospital spiital aadmissions, dm mis issi sioons, ons, ccardiovascular ardi ardi diov vas ascu cullar cu diagnoses, Possible vascular are abstracted hospital records and sent diag di agno ag nose no ses, s, aand nd ddeaths. nd eaath thss. P ossiibl os b e va vasc scul sc ular ar eevents vent ve ntts ar re ab bst stra ract ra cted ct d ffrom ro om ho hosp spit itaal re eco c rd rdss an nd se sen nt ffor nt o or review eview and cclassification laasssiffic icat a io at i n by aan n iindependent n ep nd epen nde dent nt aadjudication djud dj uddic i at a io on co comm committee. mmit mm itteee. it e O Outcome utco ut come co me ffollow-up ollo ol lowlo w up data were available for events occurring on or before and adjudicated through December 31, 2011 (median follow-up of 10.2 years). Covariates Sociodemographic covariates included age, sex, education (categorized as less than high school graduate, high school graduate, some college, and college degree or higher), health insurance status, and income (specified in quartiles). Baseline income was available and used for 80.0% of Black participants, 85.0% of Hispanic participants, and 88.3% of White participants. When baseline income was missing, data from Exam 2 were used (4.4% of Black participants, 1.2% of
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DOI: 10.1161/CIRCULATIONAHA.114.011345
Hispanic participants, and 1.2% of White participants). Neighborhood (census tract) characteristics were adjusted for included neighborhood poverty, the neighborhood social environment, and the neighborhood physical environment. Neighborhood poverty was defined as the percent of neighborhood residents who were below the U.S. Census Bureau-defined poverty threshold, based on baseline address linked to Census 2000 data.25 Survey-based information on the neighborhood social and physical environments was collected as part of the MESA Neighborhood study, an ancillary study designed to assess neighborhood conditions of potential relevance to cardiovascular disease. In addition to MESA participants, a sample of 5,988 individuals (recruited between January and August 2004) residing n the same neighborhoods as MESA participants were asked to rate several aspe ectss off th ects thei eirr ei in aspects their neighborhood via a telephone survey. Supplementing the neighborhood survey with participants ot theer th than an n tthose hosee iin ho n ME M SA reduced the potentiall ffor or same source bbias, i s,, iincreased ia ncre nc r ased the withinother MESA nneighborhood eig ghb h orhoodd sample sam ampl plee size siize for for or constructing connst strruc ructiing more mo reliable reliab rel blee subjective sub ubje j cttiv je ive neighborhood neig ne ighb hboorh orhood hood d vvariables, a ia ar i bl bles es,, and an prov pr ovid ov ided id e am ed oree re or epr p eseenta entatiive v me meas asur urre of nneighborhood eiigh ghbo borrhoo bo oodd cond oo cconditions. ond ndit itio i ns io ns..26 provided more representative measure The ne eig ighb hbbor o ho h od o social soc ociaal environment e vi en v ro onm nmen entt me en meas asur as u e wa ur wass ge gene nera ne r te tedd by ssumming u mi um ming ng 3 sscales, cales, neighborhood measure generated including neighborhood safety (a composite of three self-reported questions of safety and violence), neighborhood social cohesion (a composite of five self-reported questions on feelings of mutual trust and solidarity with neighbors), and aesthetic quality (a composite of three selfreported questions relating to noise, presence of trash and litter, and overall neighborhood attractiveness). Possible scores ranged from 3 to 15, with higher scores indicating a better social environment (Cronbach’s alpha: 0.89). The neighborhood physical environment measure was constructed by summing responses of neighborhood walking environment (4 items) and neighborhood food environment (2 items) scales. Possible scores ranged from 2 to 10
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DOI: 10.1161/CIRCULATIONAHA.114.011345
(Cronbach’s alpha: 0.75). For each neighborhood scale, conditional empirical Bayes estimates were derived to increase reliability of the measures. Additional details on the development of the scales are provided elsewhere.26 Both the neighborhood social and physical environment measures were categorized into tertiles. We also adjusted for traditional behavioral and biological CVD risk factors, including cigarette smoking, physical activity, diabetes, systolic blood pressure, total cholesterol, HDL cholesterol, and BMI. Physical activity was categorized as high (1000 MET-minutes per week of energy expenditure from recreational activity), intermediate (>0 and < 1000 MET-minutes per week), or physically inactive based on the 2008 Physical Activity Guidelines for Americans.27 Cigarette smoking was categorized as current, former, and never; alcohol use wa was as ca cate categorized ego gori rize ri zedd as ze heavy (>14 drinks per week for men and >7 drinks per week for women), moderate, or none. Diabetes Diab Di abet ab etees et es was was a defined def effin ined e as having a fasting glucose see 126 mg/dl or be bbeing in ng on on insulin or oral hypoglycemic medications hypoglycemic hyp po cm ed diccat atio onss 288. Re Res Resting stin stin ingg seated seeateed blood blood od pre pressure essur ssurre wa wass meas m measured easur ured ed tthree hree hr ee ttimes im mess aatt a si ssingle ngle visit visi vi sitt by trained si tra rain ined in ed and andd certified certi ertiifi fied ed clinic clin inic ic staff sta tafff ff using usi sinng ng a Dinamap Din nam map p PRO PRO O 100 100 0 aautomated uttom matted ooscillometric sccilllom metr metr t ic device (Critikon, (Critik ik kon on,, Ta Tamp Tampa, mpa, mp a F a, FL), L),, aand L) nd tthe h aaverage he veeraage ooff th thee la last st tw twoo me meas measurements sur urem emen em ents en t w ts was as uused. sed. se d 29 Plasmaa HDL and total cholesterol were measured by the cholesterol-oxidase method. 30 Statistical analysis All analyses were stratified by race/ethnicity. Descriptive analyses compared baseline participant characteristics by levels of residential segregation score (high: Gi* >1.96; medium: Gi* 0 – 1.96; and low: Gi* < 0). The high category corresponds to statistically significant clustering at the Į=0.05 level, and the low category corresponds to both the absence of any clustering or areas in which the group is significantly under-represented (Gi* < -1.96). These categories were combined because the number of Blacks and Hispanics living in areas where they were
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DOI: 10.1161/CIRCULATIONAHA.114.011345
significantly under-represented was very small. Baseline characteristics were also compared in those who did and did not develop incident CVD/CHD. A series of marginal Cox proportional hazards regression modeling were estimated using a robust sandwich estimator to examine the relationship between baseline continuous segregation and CVD/CHD event while accounting for any residual correlations among individuals residing in the same census tract.31, 32 Time was measured from date of the baseline exam and subjects were censored at the last contact date for outcome information if a CVD/CHD event was not observed. The proportional hazards assumption was tested by evaluating interactions of analysis time with the full complement of covariates; there was no evidence of violation. Model 1 adjusted for demographics including age, sex, and MESA study site (nativity was waas adjusted ad dju ust sted ed for for o as well for the analysis of Hispanics). We did not find evidence suggesting associations of egr greg egat eg atio at ionn wi io w th h iincident nc ncident CVD varied by MESA A st stu udy site (P forr in iinteraction teera racction ct 0.5), so findings segregation with study ar re pr ppresented esented po pool oled ed d aacross crrosss th thee si site t s. te s. M odell 2 add dittionnally ad djussteed fo djus fforr neig nneighborhood-level eig ghb hbor orho hood ho od-l od - ev -l vel are pooled sites. Model additionally adjusted ch har arac acte ac t ri te rist stic st icss through ic th hro oug gh which wh h segregation seegr greg egat eg attio ionn may mayy impact impa im paactt CVD/CHD, CVD VD/C CHD HD,, including incl in clluddin ingg neighborhood neig ne ighb ig hborrho hb hood od characteristics poverty, the neighborhood nei eigh ghbo gh borh bo rh hoo o d physical phys ph yssic ical al environment, envvir iron onme on ment me n , and nt and the th he neighborhood neig ne ighb ig hbor hb orho hood ho od social soc ocia iall environment. envi en viro vi ronm ro n ent. Thee Black (r=0.31), Hispanic (r=0.31), and White (r=-0.59) segregation scores were correlated with neighborhood poverty, but not strongly enough to preclude us from assessing their independent associations. Model 3 further adjusted for individual factors that may have been influenced by segregation: education and income. Model 4 additionally adjusted for baseline CVD risk factors including hypercholesterolemia, hypertension, diabetes, body mass index, physical activity, current alcohol use, and current cigarette smoking as potential individual-level mediators. We estimated three additional models to leverage our longitudinal data structure and more precisely operationalize our constructs. We first modeled the behavioral and biological
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DOI: 10.1161/CIRCULATIONAHA.114.011345
CVD risk factors as time-varying covariates (Model 5), and then we specified both residential segregation and CVD risk factors as time-varying (Model 6). As a secondary analysis, we also examined associations of change in segregation score with incident CVD. This was done by calculating the difference in the segregation score between each exam and baseline and including this variable as a time varying covariate in the Cox regression. For analyses of Hispanic segregation, we also tested whether the association between segregation and incident CVD varied between those of Mexican origin and those not of Mexican origin (including Dominican, Puerto Rican, Cuban, and other Hispanics) by incorporating a segregation*Mexican origin interaction term. This was motivated by prior research that has Hispanic subgroup. found associations between residential environment and health to differ by Hisp pan anic icc sub ubgr ub grou gr oupp.33, ou 34 4
Small sample sizes precluded assessing this relationship separately in the other Hispanic
ubg bgro ro oups. ups. Based Based ed d on on previous research,35 we also so te tested ested for effect ctt mod modification oddif ific ication by nativity and subgroups. acculturation. ac ccu ulturation. Nativity Nativit ityy was was dichotomized dich di chot ottom omizzed ass fo foreign-born oreiggn-boorn rn vvs. s. U US-born. S-bborn born.. Acculturation Accu Accu ulttur urat atio at io on wa wass assessed summary score length lived US born; as sse sess sssed e uusing sing si ng a su umma umma mary r sco ry co oree bbased ased as ed d oon n le leng nggth ooff ttime im me li liv vedd in n the he U S (3 ((3=US =US =U S bo orn rn;; 2=fo 22=foreign =fore reeig gn born and lived ed d iin n th thee US 20 20 yyears; ears ea r ; 1= rs 1=fo 1=foreign-born f re fo reig ignig n bo nborn rnn aand ndd llived ive vedd in tthe hee U US S 10 10-1 10-19 -199 ye year years; ars; ar s; aand nd 0=foreign born and lived in the US
