An Assessment of Census-Tract Level Socioeconomic Position As a Modifier of the Relationship Between PM 2.5 Concentrations and Cardiovascular Emergency Department Visits in Missouri

Ambient PM2.5 exposure elevates the risk for cardiovascular disease morbidity (CVDM). The aim of this study is to characterize which area-level measures of socioeconomic position (SEP) modify the relationship between PM2.5 exposure and CVDM in Missouri at the census-tract (CT) level. We use individual level Missouri emergency department (ED) admissions data (n = 3,284,956), modeled PM2.5 data, and yearly census tract data from 2012-2016 to conduct a two-stage analysis. Stage one uses a case-crossover approach with conditional logistic regression to establish the baseline risk of ED visits associated with interquartile range (IQR) changes in PM2.5. In the second stage, we use multivariate meta-regression to examine how census tract level SEP modifies the relationship between ambient PM2.5 exposure and CVDM. We find that overall, ambient PM2.5 exposure is associated with increased risk for CVDM. We test effect modification in statewide and urban census tracts, and in the warm-season only. Effect modification results suggest that among SEP measures, poverty is most consistently associated with increased risk for CVDM. For example, across Missouri the highest poverty CTs are at an elevated risk for CVDM [OR = 1.010 (95% CI 1.007, 1.014)] compared to the lowest poverty CTs [OR = 1.004 (95% CI 1.000, 1.008)]. Other SEP modifiers generally display an inconsistent or null effect. Overall, we find some evidence that area-level SEP modifies the relationship between ambient PM2.5 exposure and CVDM, and suggest that the relationship between air-pollution, area-level SEP, and CVDM may be sensitive to spatial scale. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement NIEHS R01ES027892 NIEHS T32ES012870 ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Institutional Review Board (IRB) at Emory University approved this study and granted an exemption from informed consent requirements. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Exposure and meteorological data are available online at: (exposure) (meteorological) Patient health information are available upon reasonable request to the author, IRB approval, and State of Missouri Department of Health and Senior Services