Association of Long-term Exposure to Particulate Air Pollution With Cardiovascular Events in California.

Importance: Long-term exposure to fine particulate air pollution (PM2.5) is a known risk factor for cardiovascular events, but controversy remains as to whether the current National Ambient Air Quality Standard (12 µg/m3 for 1-year mean PM2.5) is sufficiently protective. Objective: To evaluate the associations between long-term fine particulate air pollution and cardiovascular events using electronic health record and geocoded address data. Design, Setting, and Participants: This retrospective cohort study included adults in the Kaiser Permanente Northern California integrated health care system during 2007 to 2016 and followed for up to 10 years. Study participants had no prior stroke or acute myocardial infarction (AMI), and lived in Northern California for at least 1 year. Analyses were conducted January 2020 to December 2022. Exposure: Long-term exposure to PM2.5. Individual-level time-varying 1-year mean PM2.5 exposures for every study participant were updated monthly from baseline through the end of follow-up, accounting for address changes. Main Outcomes and Measures: Incident AMI, ischemic heart disease (IHD) mortality, and cardiovascular disease (CVD) mortality. Cox proportional hazards models were fit with age as time scale, adjusted for sex, race and ethnicity, socioeconomic status, smoking, body mass index, baseline comorbidities, and baseline medication use. Associations below the current regulation limit were also examined. Results: The study cohort included 3.7 million adults (mean [SD] age: 41.1 [17.2] years; 1 992 058 [52.5%] female, 20 205 [0.5%] American Indian or Alaskan Native, 714 043 [18.8%] Asian, 287 980 [7.6%] Black, 696 796 [18.4%] Hispanic, 174 261 [4.6%] multiracial, 1 904 793 [50.2%] White). There was a 12% (95% CI, 7%-18%) increased risk of incident AMI, a 21% (95% CI, 13%-30%) increased risk of IHD mortality, and an 8% (95% CI, 3%-13%) increased risk of CVD mortality associated with a 10 µg/m3 increase in 1-year mean PM2.5. PM2.5 exposure at moderate concentrations (10.0 to 11.9 µg/m3) was associated with increased risks of incident AMI (6% [95% CI, 3%-10%]) and IHD mortality (7% [95% CI, 2%-12%]) compared with low concentrations (less than 8 µg/m3). Conclusions and Relevance: In this study, long-term PM2.5 exposure at moderate concentrations was associated with increased risks of incident AMI, IHD mortality, and CVD mortality. This study's findings add to the evidence that the current regulatory standard is not sufficiently protective.

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

Fine particulate matter (PM2.5) is a known risk factor for cardiovascular disease (CVD). Neighborhood walkability and greenness may also be associated with CVD, but there is limited evidence on their joint or interacting effects with PM2.5. Methods: Cox proportional hazard models were used to estimate the risk of CVD mortality among adults with a history of acute myocardial infarction and/or stroke living in Northern California. We assessed the independent and joint effects of walkability, greenness (Normalized Differentiated Vegetation Index [NDVI]), and PM2.5 at residential addresses, controlling for age, sex, race/ethnicity, comorbidities, BMI, smoking, revascularization, medications, and socioeconomic status. Results: Greenness had a nonlinear association with CVD mortality (P = 0.038), with notably protective effects (HR = 0.87 [95% confidence interval {CI} = 0.78, 0.97]) at higher greenness levels (NDVI ≥ 0.3) and moderate attenuation after adjusting for PM2.5 (HR = 0.92 [95% CI = 0.82, 1.03]) per 0.1 increase in NDVI. Walkability had no independent effect on CVD mortality. PM2.5 had a strong independent effect in models adjusted for greenness and walkability (HR = 1.20 [95% CI = 1.08, 1.33)) per 10 µg/m3 increase in PM2.5. There was an interaction between walkability and PM2.5 (P = 0.037), where PM2.5 had slightly stronger associations in more walkable than less walkable neighborhoods (HR = 1.23 [95% CI = 1.06, 1.42] vs. 1.17 [95% CI = 1.04, 1.32]) per 10 µg/m3 increase in PM2.5. Greenness had no interaction with PM2.5 (P = 0.768) nor walkability (P = 0.385). Conclusions: High greenness may be protective of CVD mortality among adults with CVD history. PM2.5 associated CVD mortality risk varies slightly by level of neighborhood walkability, though these small differences may not be clinically meaningful.

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

Background Previous studies have found associations between fine particulate matter <2.5 µm in diameter (PM2.5) 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 PM2.5-related CVD events and whether current regulation levels for PM2.5 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 PM2.5 exposure estimates based on residential locations. Cox proportional hazard models estimated risks of stroke, acute myocardial infarction, and cardiovascular mortality associated with PM2.5 exposure, adjusting for multiple covariates. Secondary analyses estimated risks below federal and state regulation levels (12 µg/m3 for 1-year mean PM2.5). A 10-µg/m3 increase in 1-year mean PM2.5 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/m3 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/m3 increase in 1-year mean PM2.5. Conclusions Adults with a history of CVD are susceptible to the effects of PM2.5 exposure, particularly on CVD mortality. Increased risks observed at exposure levels <12 µg/m3 highlight that current PM2.5 regulation levels may not be protective for this susceptible population.

Particulate Matter and Cardiovascular Risk in Adults with Chronic Obstructive Pulmonary Disease.

Rationale: People with chronic obstructive pulmonary disease (COPD) have an increased risk of cardiovascular disease and may be more susceptible to air pollution exposure. However, no study has examined the association between long-term fine particulate matter exposure (≤2.5 µm in aerodynamic diameter) and risk of cardiovascular events in this potentially vulnerable population. Objectives: To estimate the association between long-term fine particulate matter and risk of cardiovascular events among adults with COPD. Methods: This retrospective cohort study included 169,714 adults with COPD who were members of the Kaiser Permanente Northern California health plan during 2007-2016. Electronic health record data were linked to 1 km modeled particulate matter ≤2.5 µm in aerodynamic diameter exposure estimates. We fit Cox proportional hazard models, adjusting for age, sex, race/ethnicity, calendar year, smoking, body mass index, comorbidities, medications, and socioeconomic status. In low exposure analyses, we examined effects below the current regulation limit (12 µg/m3). Measurements and Main Results: Among adults with COPD, a 10-µg/m3 increase in 1-year mean fine particulate matter exposure was associated with an elevated risk of cardiovascular mortality (hazard ratio, 1.10; 95% confidence interval [CI], 1.01-1.20). Effects were stronger in low exposure analyses (hazard ratio, 1.88; 95% CI, 1.56-2.27). Fine particulate matter exposure was not associated with acute myocardial infarction or stroke in overall analyses. Conclusions: Long-term fine particulate matter exposure was associated with an increased risk of cardiovascular mortality among adults with COPD. Current regulations may not sufficiently protect those with COPD.

Long-Term PM2.5 Exposure and Risks of Ischemic Heart Disease and Stroke Events: Review and Meta-Analysis.

Background Fine particulate matter <2.5 µm in diameter (PM2.5) has known effects on cardiovascular morbidity and mortality. However, no study has quantified and compared the risks of incident myocardial infarction, incident stroke, ischemic heart disease (IHD) mortality, and cerebrovascular mortality in relation to long-term PM2.5 exposure. Methods and Results We sought to quantitatively summarize studies of long-term PM2.5 exposure and risk of IHD and stroke events by conducting a review and meta-analysis of studies published by December 31, 2019. The main outcomes were myocardial infarction, stroke, IHD mortality, and cerebrovascular mortality. Random effects meta-analyses were used to estimate the combined risk of each outcome among studies. We reviewed 69 studies and included 42 studies in the meta-analyses. In meta-analyses, we found that a 10-µg/m3 increase in long-term PM2.5 exposure was associated with an increased risk of 23% for IHD mortality (95% CI, 15%-31%), 24% for cerebrovascular mortality (95% CI, 13%-36%), 13% for incident stroke (95% CI, 11%-15%), and 8% for incident myocardial infarction (95% CI, -1% to 18%). There were an insufficient number of studies of recurrent stroke and recurrent myocardial infarction to conduct meta-analyses. Conclusions Long-term PM2.5 exposure is associated with increased risks of IHD mortality, cerebrovascular mortality, and incident stroke. The relationship with incident myocardial infarction is suggestive of increased risk but not conclusive. More research is needed to understand the relationship with recurrent events.