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

Abstract

ImportanceLong-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.ObjectiveTo evaluate the associations between long-term fine particulate air pollution and cardiovascular events using electronic health record and geocoded address data.Design, Setting, and ParticipantsThis 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.ExposureLong-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 MeasuresIncident 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.ResultsThe 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 RelevanceIn 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.

Analysis of Heat Exposure During Pregnancy and Severe Maternal Morbidity

“…As an alternative method to the Cox proportional hazards model, the discrete-time approach is flexible and can be used to estimate associations over the event time based on the proportional hazards assumption or obtain estimates for different time points to relax the assumption. 26,[37][38][39] In this study, we estimated associations based on the proportional hazards assumption by using the discrete-time method in our main analysis and compared the results with that of the Cox proportional hazards model in the sensitivity analysis. We examined associations with long-term heat exposure during the entire pregnancy and by trimester.…”

“…We examined effect modification on the multiplicative scale of entire-pregnancy associations for the primary outcome by maternal age, race and ethnicity, education level, income level, smoking, season of conception, and green space exposure using interaction terms. 39 For the season of conception, we examined associations in the cold season (November to April) vs the warm season (May to October). For green space exposure, we examined effect modification by different levels (high [Ն50th] vs low [<50th]) of exposure to total green space, trees, low-lying vegetation, and grass in separate models.…”

“…We examined effect modification on the multiplicative scale of entire-pregnancy associations for the primary outcome by maternal age, race and ethnicity, education level, income level, smoking, season of conception, and green space exposure using interaction terms . For the season of conception, we examined associations in the cold season (November to April) vs the warm season (May to October).…”

Increasing disparities in air pollution health burdens in the United States

“…Akinbami et al 48 found that children belonging to ethnoracial minority groups had as high or higher relative risk for asthma diagnoses than non-Hispanic white children, and Spiller et al 49 showed uniform RR estimates, rather than race-ethnicity specific estimates, underestimated pollution-related health impacts for minority communities. However, the literature on this topic is not consistent: Alexeeff et al 50 did not find a difference in the association between exposure to PM2.5 and COPD by race or ethnicity, and Parker et al 51 similarly found that the association between PM2.5 and heart disease mortality was not statistically different for non-Hispanic white adults versus Black or Hispanic adults. Since the literature remains inconsistent on this topic, it is unknown how race-and ethnicity-specific RR estimates would impact the findings uncovered herein.…”

Prioritizing the Exposome to Reduce Cardiovascular Disease Burden

“…Since then, there has been greater recognition of the risks associated with climate change, pollutants, and the built environment, 2 and several studies have demonstrated associations with cardiovascular risk factors 3 and acute cardiovascular events. 4 However, we have lacked comprehensive tools to measure and track the dynamic nature of exposures at an individual and geographic level.…”