Particulate Air Pollution and Risk of Cardiovascular Events Among Adults With a History of Stroke or Acute Myocardial Infarction

Abstract

Background Previous studies have found associations between fine particulate matter <2.5 µm in diameter (PM 2.5 ) and increased risk of cardiovascular disease (CVD) among populations with no CVD history. Less is understood about susceptibility of adults with a history of CVD and subsequent PM 2.5 ‐related CVD events and whether current regulation levels for PM 2.5 are protective for this population. Methods and Results This retrospective cohort study included 96 582 Kaiser Permanente Northern California adults with a history of stroke or acute myocardial infarction. Outcome, covariate, and address data obtained from electronic health records were linked to time‐varying 1‐year mean PM 2.5 exposure estimates based on residential locations. Cox proportional hazard models estimated risks of stroke, acute myocardial infarction, and cardiovascular mortality associated with PM 2.5 exposure, adjusting for multiple covariates. Secondary analyses estimated risks below federal and state regulation levels (12 µg/m 3 for 1‐year mean PM 2.5 ). A 10‐µg/m 3 increase in 1‐year mean PM 2.5 exposure was associated with an increase in risk of cardiovascular mortality (hazard ratio [HR], 1.20; 95% CI, 1.11–1.30), but no increase in risk of stroke or acute myocardial infarction. Analyses of <12 µg/m 3 showed increased risk for CVD mortality (HR, 2.31; 95% CI, 1.96–2.71), stroke (HR, 1.41; 95% CI, 1.09–1.83]), and acute myocardial infarction (HR, 1.51; 95% CI, 1.21–1.89) per 10‐µg/m 3 increase in 1‐year mean PM 2.5 . Conclusions Adults with a history of CVD are susceptible to the effects of PM 2.5 exposure, particularly on CVD mortality. Increased risks observed at exposure levels <12 µg/m 3 highlight that current PM 2.5 regulation levels may not be protective for this susceptible population.

Joint associations between neighborhood walkability, greenness, and particulate air pollution on cardiovascular mortality among adults with a history of stroke or acute myocardial infarction

“…There was substantial increased risk of CVD mortality associated with PM 2.5 exposure (HR = 1.20 [95% CI = 1.08, 1.33] per 10 μg/m 3 increase in 1-year average PM 2.5 ) (model 3), as we have reported previously. 36 Furthermore, we found no change in these harmful effects after adjusting for greenness and walkability (models 4–5). The shape of association between PM 2.5 and CVD mortality appeared to be linear (Figure 1 C, P = 0.950).…”

“…33–35 The study cohort has been described in detail previously. 36 Briefly, subjects had to be KPNC members for at least one year, had at least one outpatient (nonemergency) visit, and lived in the 35 county study region for at least 1 year at an address that was successfully geocoded and linked to the air pollution, walkability, and Normalized Differentiated Vegetation Index (NDVI) data (see eFigure 1; http://links.lww.com/EE/A179 for study region). Study follow-up began on 1 January 2007 and ended on 31 December 2016.…”

“…Individual-level baseline covariates were extracted from EHRs and included age, sex, self-reported race/ethnicity (Non-Hispanic White, Hispanic White, Hispanic [any race], Black, American Indian/Alaska Native, Asian/Pacific Islander, Multiple Races), hypertension (HTN), hyperlipidemia, diabetes, CVD history (AMI only, stroke only, both AMI and stroke), body mass index (BMI), smoking status (never, former, current), revascularization procedures (percutaneous coronary intervention and coronary artery bypass graft), statin medication use, HTN medication use (only among those with a HTN diagnosis), and Medicaid insurance (indicator of socioeconomic status [SES]). 36 Another indicator of SES measured at the block-group level from Census data included high school education attainment (percent with less than high school diploma). CVD history was defined as prior stroke or AMI compiled from inpatient and outpatient data recorded in the EHR.…”

“…CVD history was defined as prior stroke or AMI compiled from inpatient and outpatient data recorded in the EHR. 36 For the small percentage of subjects with missing data on sex (0.0024%), race/ethnicity (0.64%), smoking status (3.01%), and BMI (1.99%), we did single data imputation using the fully conditional method. 46 …”

“…We first assessed these interactions using continuous variables, and then in categories since interactions between continuous variables can be difficult to interpret. Categories were as follows: PM 2.5 (μg/m 3 ) (low: ≤9, moderate: 9–12, high: >12) as previously defined, 36 with concentrations above the state/federal regulation limit defined as high; walkability index (low: ≤6.67, moderate: 6.67–13.33, high: >13.33) using equal intervals 16 ; and NDVI (low: ≤0.2, moderate: 0.2–0.3, high: >0.3) based on its distribution. We then estimated interactions for walkability/PM 2.5 , greenness/PM 2.5 , and greenness/walkability pairs.…”