Ambient air pollution and cardiovascular diseases: An umbrella review of systematic reviews and meta-analyses

Abstract

The available evidence on the effects of ambient air pollution on cardiovascular diseases (CVDs) has increased substantially. In this umbrella review, we summarized the current epidemiological evidence from systematic reviews and meta-analyses linking ambient air pollution and CVDs, with a focus on geographical differences and vulnerable subpopulations. We performed a search strategy through multiple databases including articles between 2010 and 31 January 2021. We performed a quality assessment and evaluated the strength of evidence. Of the 56 included reviews, the most studied outcomes were stroke (22 reviews), all-cause CVD mortality, and morbidity (19). The strongest evidence was found between higher short- and long-term ambient air pollution exposure and all-cause CVD mortality and morbidity, stroke, blood pressure, and ischemic heart diseases (IHD). Short-term exposures to particulate matter <2.5 μm (PM_2.5 ), <10 μm (PM₁₀ ), and nitrogen oxides (NO_x ) were consistently associated with increased risks of hypertension and triggering of myocardial infarction (MI), and stroke (fatal and nonfatal). Long-term exposures of PM_2.5 were largely associated with increased risk of atherosclerosis, incident MI, hypertension, and incident stroke and stroke mortality. Few reviews evaluated other CVD outcomes including arrhythmias, atrial fibrillation, or heart failure but they generally reported positive statistical associations. Stronger associations were found in Asian countries and vulnerable subpopulations, especially among the elderly, cardiac patients, and people with higher weight status. Consistent with experimental data, this comprehensive umbrella review found strong evidence that higher levels of ambient air pollution increase the risk of CVDs, especially all-cause CVD mortality, stroke, and IHD. These results emphasize the importance of reducing the alarming levels of air pollution across the globe, especially in Asia, and among vulnerable subpopulations.

Keywords: ambient air pollution; cardiovascular diseases; nitrogen oxides; particulate matter; umbrella review.

Fig. 1

Graph showing population‐weighted annual PM_2.5 (where PM is particulate matter) averages (2019) and air quality standards (Note: presenting the two most polluted and two least polluted countries in each region) [8].

Fig. 2

Flowchart of the included reviews.

Fig. 3

Effect estimates of the association between short‐term exposure to PM_2.5 and CVDs. Note: we selected the main effect estimate from the meta‐analyses if multiple effect estimates were available for each CVD outcome in the same meta‐analysis. Effect estimates are estimated per 10 μg/m³ range increase in PM_2.5. Abbreviations: BP, blood pressure; CeVD, cerebrovascular diseases; CVD, cardiovascular diseases; ICD, implantable cardioverter defibrillator; IHD, ischemic heart diseases; MI, myocardial infarction; PM, particulate matter. ^*Beta coefficient (linear regression) for change in systolic and diastolic values per increase of PM_2.5.

Fig. 4

Effect estimates of the association between short‐term exposure to NO_x/NO₂ and CVDs. Note: we selected the main effect estimate from the meta‐analyses if multiple effect estimates were available for each CVD outcome in the same meta‐analysis. Effect estimates are estimated per 10 μg/m³ range increase in NO_x/NO_2. Abbreviations: BP, blood pressure; CeVD, cerebrovascular diseases; CVD, cardiovascular diseases; IHD, ischemic heart diseases; MI, myocardial infarction. ^*Beta coefficient (linear regression) for change in systolic and diastolic values per increase of NO_x/NO₂.

Fig. 5

Effect estimates of the association between long‐term exposure to PM_2.5 and CVDs. Note: we selected the main effect estimate from the meta‐analyses if multiple effect estimates were available for each CVD outcome in the same meta‐analysis. Effect estimates are estimated per 10 μg/m³ range increase in PM_2.5. Abbreviations: ABI, ankle‐brachial index, BP, blood pressure; CAC, coronary artery calcification; CeVD, cerebrovascular diseases; CIMT, carotid intima‐media thickness test; CVD, cardiovascular diseases; IHD, ischemic heart diseases; MI, myocardial infarction; PM, particulate matter. ^*Beta coefficient (linear regression) for change in systolic, diastolic, CIMT, CAC, or ABI values per increase of PM_2.5.

Fig. 6

Effect estimates of the association between long‐term exposure to NO_x/NO₂ and CVDs. Note: we selected the main effect estimate from the meta‐analyses if multiple effect estimates were available for each CVD outcome in the same meta‐analysis. Effect estimates are estimated per 10 μg/m³ range increase in NO_x/NO₂. Abbreviations: BP, blood pressure; CVD, cardiovascular diseases; IHD, ischemic heart diseases. ^*Beta coefficient (linear regression) for change in systolic or diastolic values per increase of NO_x/NO₂.

Fig. 7

Potential biological pathways between air pollution and cardiovascular diseases.