01.12.2021 | Review article | Ausgabe 1/2021
Open Access
Association between exposure to ambient air pollution and hospital admission, incidence, and mortality of stroke: an updated systematic review and meta-analysis of more than 23 million participants
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Abbreviations
PM2.5
Particulate matter with aerodynamic diameter less than 2.5 μm
PM10
Particulate matter with aerodynamic diameter less than 10 μm
NO2
Nitrogen dioxide
SO2
Sulfur dioxide
CO
Carbon monoxide
O3
Ozone
OR
Odds ratio
HR
Hazard ratio
CI
Confidence interval
e.g.
For example
GBD
The Global Burden of Disease Study
CVD
Cardiovascular diseases
DALYs
Disability-adjusted life years
RR
Risk ratio
PRISMA
The Preferred Reporting Items for Systematic Review and Meta-analyses
NOx
Nitrogen oxides
IQR
Interquartile range
SD
Standard deviation
NOS
The Newcastle-Ottawa Scale
SE
Standard error
China-PAR
Atherosclerotic Cardiovascular Disease Risk in China (China-PAR) project
ICH
Intracerebral hemorrhage
IS
Ischemic stroke
REGARDS cohort
Reasons for Geographic and Racial Differences in Stroke Cohort
PPS
Primary prevention study
CNBSS
Canadian National Breast Screening Study
HS
Hemorrhagic stroke
ESCAPE Project
The European Study of Cohorts for Air Pollution Effects
AOD
Aerosol optic depth
ISSeP
The Scientific Institute of Public Services
CMAQ
Community Multiscale Air Quality model
QOED
The Qingyue Open Environmental Data Center
USEPA
The US Environmental Protection Agency
HBM
Hierarchical Bayesian Model
EPA
The Taiwanese Environmental Protection Administration
EPD
The Environmental Protection Department
LUR
Land-use regression model
IDW
Inverse distance weighting
Introduction
Stroke, characterized by acute cerebral blood circulation disorder, is caused by artery stenosis, occlusion, or rupture caused by various inducing factors in patients with cerebrovascular diseases [
1]. Stroke has become a leading contributor to the global burden of disease and the second leading cause of death worldwide [
2,
3]. According to the Global Burden of Disease Study (GBD) report, there were approximately 80.1 million stroke patients, and 5.5 million deaths were attributed to stroke in 2016 globally [
4]. Considering stroke is characterized with high incidence, high mortality, and contribute to severe burden disease, identifying potential risk factor of stroke is of great significance for public health. In parallel, air pollution has also been regarded as one of the major environmental problems and a risk factor of many cardiovascular diseases (CVD), including stroke [
5]. GBD 2019 showed that air pollution was globally the sixth leading cause of stroke death during 1990 to 2017, and 28.1% disability-adjusted life years (DALYs) of stroke attribute to environmental factors exposure [
6,
7].
Air pollution is the most significant environmental risk factor for all-cause mortality [
8]. Increasing number of human epidemiologic studies has been conducted to assess the potential association between air pollution exposure and stroke admission, incidence, and mortality in recent years. However, the results were inconsistent, and the associations between exposure to air pollution and stroke have not been fully understood. Some studies reported positive association between air pollution exposure and stroke hospital admission/incidence/mortality, whereas others did not [
4,
9–
14]. For example, Huang et al. 2019 indicated that exposure to PM
2.5 was associated with increased stroke incidence and the adjusted risk ratio (RR) was 1.130 (95%CI: 1.090, 82 1.170) for each increase of 10 μg/m
3 in n PM
2.5 concentration [
4]. The adjusted risk ratio (RR) was 1.130 (95% CI 1.090, 1.170) for each increase of 10 μg/m
3 in PM
2.5 concentration, while Wing et al. suggested no association was found between PM
2.5 exposure and stroke incidence (RR = 0.950, 95% CI 0.710, 1.280) [
11]. Previous meta-analyses have explored the associations between air pollution exposure and stroke [
15–
19]. However, these studies were mainly focused on the studies of particulate matter (PM
2.5, particulate matter with aerodynamic diameter less than 2.5 μm; PM
10, particulate matter with aerodynamic diameter less than 10 μm) and stroke outcomes [
16–
19]; results of gas air pollutants (NO
2, nitrogen dioxide; SO
2, sulfur dioxide; CO, carbon monoxide; O
3, ozone) were scarce. Moreover, to the best of our knowledge, more than 30 studies exploring the association between air pollution exposure and stroke, especially conducted from the multi-city level and with large sample sizes, were published after the most recent meta-analysis. The more recent and comprehensive studies should be included in the meta-analysis to conclude an updated pooled effect estimate.
Anzeige
We therefore conducted an updated systematic review and meta-analysis to assess the association between 6 main air pollutants (PM
2.5, PM
10, NO
2, SO
2, CO, and O
3) and 3 stroke outcomes (hospital admission, incidence, and mortality). This systematic review and meta-analysis was performed according to the guidelines of the Preferred Reporting Items for Systematic Review and Meta-analyses (PRISMA) criteria (Table
S1).
Methods
Search strategy
Literature was searched in three databases (PubMed, Embase, and Web of Science), with published date until 1 February 2020. The search strategy was pairwise of combinations of terms concerning air pollution (e.g., air pollution, particulate matter, particles, PM
2.5, PM
10, nitrogen oxides (NOx), NO
2, SO
2, CO, and O
3) and stroke (e.g., stroke, cerebrovascular disease, cerebrovascular disorder, cerebral hemorrhage, cerebral infarction, subarachnoid hemorrhage).
We first selected articles by screening titles and abstracts and then the full texts of potentially eligible studies were further evaluated. Reference lists of all the included studies were also manually searched. Literature selection was finished by two independent authors (ZP N and FF L), and conflicts between the two authors were resolved by discussing with an arbitrator (H X).
Inclusion and exclusion criteria
Articles that met the following criteria were included: (1) provided quantitative measure of the associations between air pollution exposure with stroke admission, incidence, and/or mortality (relative risk (RR), odds ratio (OR), or hazard ratio (HR), and their 95% confidence interval (95%CI); (2) cohort, cross-sectional, time series, cross-sectional, case-control, case-crossover, or panel studies; (3) focused on outdoor (ambient) air pollution exposure but not indoor air pollution; (4) original peer-reviewed human subject research studies; (5) published in English. Studies were excluded if they were (1) toxicological studies, summaries, or reviews, and (2) articles without effect estimates after contacting the authors. In addition, for more than one article conducted from the same population, only the most recent studies were included.
Anzeige
Data extraction
Data were extracted from all eligible studies, including the following: (1) study characteristics (first author, published year, study location, and period); (2) study population (sample size, proportion of males, range of age, mean age); (3) outcome (type of stroke and outcome was admission, incidence, and/or mortality); (4) air pollution assessment method and increment of air pollution used in effect estimates (per interquartile range (IQR), standard deviation (SD), or per 10 μg/m
3); (5) effect estimates of the association between air pollution and stroke risk (OR, RR, HR with 95% CI). The effect estimates of single-pollutant model, generally called “main model” or “fully adjusted model,” were extracted [
20].
Quality assessment
Two authors (ZP N and FF L) worked independently, and inconsistencies in quality assessment were resolved through discussion. We employed the Newcastle-Ottawa Scale (NOS) to evaluate the quality of included studies. The NOS Tool has designed 8 items to assess the critical appraisal of the potential risk of bias. Total score of NOS ranged from 0–9. Study score higher than or equal to 7 was regarded as high-quality; otherwise, the study was regarded as “low quality” [
21].
Statistical analyses
This meta-analysis focused on examining the association between air pollution and three stroke outcomes, including admission, incidence, and/or mortality. We extracted effect estimates (OR, HR, RR, and 95%CI) from individual studies and then converted them into a standardized form of per 10 μg/m
3 increases in air pollution. The significance of the pooled OR, RR, or HR was determined by the
Z test [
22], and
p value less than 0.05 was considered statistically significant. Standard error (SE) for each effect estimate was calculated by using the formula: (upper limit − lower limit)/3.92.
Heterogeneity among studies was evaluated using
I2 statistics and
Q test [
23]. If the values of
I2 > 50% or
p < 0.01, the heterogeneity was “high” and random effect model was used to pool estimates. Otherwise, heterogeneity was considered as “low or moderate,” and fixed-effect model was used to pool estimates.
Begg’s test and Egger’s test were conducted to assess publication bias. The influence of individual studies on the pooled estimates was examined by removing each study from the analysis one by one. Moreover, we also performed sensitivity analysis and subgroup analysis to evaluate if the exposure period would change the significance of the pooled results. Because long-term studies were limited, sensitivity analysis was conducted by omitting long-term exposure (cohort) studies. Subgroup analysis was only performed if the number of short-term exposure studies or long-term exposure studies was more than 3. Publication bias and sensitivity analysis were only performed if the number of included studies was more than 5. All statistical analysis was performed in Stata version 15.0 (StataCorp, College Station, TX, USA).
Results
Literature search and characteristics of included studies
After removing duplicates, 737 records were identified in the initial literature search. By reviewing title and abstracts, 93 studies were downloaded for full-text reading. According to the inclusion and exclusion criteria, a total of 68 studies were included in our meta-analysis (Fig.
1).
Fig. 1
Flow chart of selecting studies for meta-analysis
×
Table
1 provides the characteristics of 68 studies included in meta-analysis. As for air pollution involved in the study, there were 26 studies that reported the association between air pollution exposure and stroke hospital admission, 19 reported air pollution exposure and stroke incidence, 19 reported air pollution exposure and stroke mortality, and 3 reported both stroke incidence and mortality. The sample size of included studies ranged between 407 and 8,834,533; more than 23 million participants were included in meta-analysis eventually. Furthermore, the studies included were conducted from 18 countries. Time-series and cross-sectional were the most commonly adopted study designs. In our meta-analysis, all 68 included studies were considered as “high quality,” and the average NOS score was 8.26 for all studies (Table
S2)
Fixed-site monitoring station operated by the closest spatial distance to the county center. Daily air pollution data for PM2.5 and O3 concentrations were collected from the National Air pollution Monitoring System
20 monitoring site and data operated by the Department of the Environment (Seoul)
Ischemic stroke
Mortality
PM2.5 particulate matter with aerodynamic diameter less than 2.5 μm,
PM10 particulate matter with aerodynamic diameter less than 10 μm,
SO2 sulfur dioxide,
NO2 nitrogen dioxide,
CO carbon monoxide,
O3 ozone,
China-PAR Atherosclerotic Cardiovascular Disease Risk in China (China-PAR) project,
ICH intracerebral hemorrhage,
IS ischemic stroke,
REGARDS Cohort Reasons for Geographic and Racial Differences in Stroke Cohort,
PPS primary prevention study,
CNBSS Canadian National Breast Screening Study,
HS hemorrhagic stroke,
ESCAPE Project the European Study of Cohorts for Air Pollution Effects,
AOD aerosol optic depth,
ISSeP the Scientific Institute of Public Services,
CMAQ Community Multiscale Air Quality model,
QOED the Qingyue Open Environmental Data Center,
USEPA the US Environmental Protection Agency,
HBM Hierarchical Bayesian Model,
EPA the Taiwanese Environmental Protection Administration,
EPD the Environmental Protection Department,
LUR land use regression model,
IDW inverse distance weighting
.
Air pollution and stroke hospital admission
A total of 29 studies were performed to assess the association for air pollution and stroke hospital admission, and the results were inconsistent. Most studies showed a positive correlation between exposure to air pollution and the risk of hospital admission for stroke. In meta-analysis, we enrolled 13 studies on PM
2.5, 11 studies on PM
10 and NO
2, 10 studies on SO
2 and O
3, and 6 studies on CO with stroke hospital admission and suggested an increased stroke hospital admission risk after air pollution exposure. The pooled odds ratio (OR) of stroke with a 10 μg/m
3 increase in PM
2.5, PM
10, SO
2, NO
2, CO, and O
3 was 1.008 (95% CI 1.005, 1.011), 1.004 (95% CI 1.001, 1.006), 1.013 (95% CI 1.007, 1.020), 1.023 (95% CI 1.015, 1.030), 1.000 (95% CI 1.000, 1.001), and 1.002 (95% CI 1.000, 1.003), respectively (Table
2, Figure
S1-
S6). Heterogeneity among studies was significant (
I2 ≥ 50%,
p < 0.001).
Table 2
Association between exposure to air pollution and stroke hospital admission (per 10 μg/m
3 increment)
Air pollution
Hospital admission
Heterogeneity
NO.
HR (95% CI)
I2 (%)
P
PM
2.5
19
1.008 (1.005, 1.011)
96.6
0.000
PM
10
15
1.004 (1.001, 1.006)
92.7
0.000
SO
2
13
1.013 (1.007, 1.020)
94.5
0.000
NO
2
15
1.023 (1.015, 1.030)
92.6
0.000
CO
8
1.000 (1.000, 1.001)
92.7
0.000
O
3
15
1.002 (1.000, 1.003)
80.2
0.000
HR hazard ratio,
NO. number,
PM2.5 particulate matter with aerodynamic diameter less than 2.5 μm,
PM10 particulate matter with aerodynamic diameter less than 10 μm,
SO2 sulfur dioxide,
NO2 nitrogen dioxide,
CO carbon monoxide,
O3 ozone
Anzeige
Air pollution and stroke incidence
Twenty-three studies have investigated the association of air pollution on stroke incidence (Table
1). For meta-analysis, we extracted 18 studies on PM
2.5, 13 studies on PM
10, 10 studies on O
3, 7 studies on NO
2, and 4 studies on SO
2 and CO. Ten of these studies suggested increased risks for stroke incidence for at least one of the investigated pollutants. Meta-analysis showed that exposure to PM
2.5, SO
2, and NO
2 was associated with increased risks of stroke incidence, and the pooled HR with a 10 μg/m
3 increase was 1.048 (95% CI 1.020, 1.076), 1.002 (95% CI 1.000, 1.003), 1.002 (95% CI 1.000, 1.003), respectively. However, no significant differences were found in associations of PM
10, CO, O
3, and stroke incidence (Table
3, Figure
S7-
S12).
Table 3
Association between exposure to air pollution and stroke incidence (per 10 μg/m
3 increment)
Air pollution
Incidence
Heterogeneity
NO.
OR (95% CI)
I2 (%)
P
PM
2.5
18
1.048 (1.020, 1.076)
82.3
0.000
PM
10
13
1.017 (0.981, 1.055)
51.9
0.010
SO
2
4
1.002 (1.000, 1.003)
20.3
0.288
NO
2
7
1.002 (1.000, 1.003)
0.0
0.512
CO
5
0.999 (0.997, 1.001)
0.0
0.763
O
3
10
0.999 (0.999, 1.000)
34.1
0.135
OR odds ratios,
NO. number,
PM2.5 particulate matter with aerodynamic diameter less than 2.5 μm,
PM10 particulate matter with aerodynamic diameter less than 10 μm,
SO2 sulfur dioxide,
NO2 nitrogen dioxide,
CO carbon monoxide,
O3 ozone
Air pollution and stroke mortality
Twenty-two population-based studies have explored the association for exposure to air pollution and stroke mortality. As for meta-analysis, 11 articles on PM
2.5, 10 articles on NO
2, 9 articles on PM
10, 6 articles on O
3, and 4 articles on CO exposure were included. Meta-analysis showed that exposure to ambient PM
2.5 (OR = 1.008 95% CI 1.005, 1.012, per 10 μg/m
3 increment), PM
10 (OR = 1.006, 95% CI 1.003, 1.010, per 10 μg/m
3 increment), SO
2 (OR = 1.006, 95% CI 1.005, 1.008, per 10 μg/m
3 increment), and NO
2 (OR = 1.009, 95% CI 1.003, 1.016, per 10 μg/m
3 increment) was associated with increased risks of mortality due to stroke. No significant difference was shown in association between CO, O
3 exposure, and stroke mortality (Table
4, Figure
S13-
S18).
Table 4
Association between exposure to air pollution and stroke mortality (per 10 μg/m
3 increment)
Air pollution
Mortality
Heterogeneity
NO.
OR (95% CI)
I2 (%)
P
PM
2.5
12
1.008 (1.005, 1.012)
89.2
0.000
PM
10
10
1.006 (1.003, 1.010)
83.3
0.000
SO
2
6
1.006 (1.005, 1.008)
45.8
0.100
NO
2
10
1.009(1.003, 1.016)
70.1
0.000
CO
5
1.045 (0.980, 1.115)
50.6
0.091
O
3
6
1.005 (0.999, 1.010)
84.8
0.000
OR odds ratios,
NO. number,
PM2.5 particulate matter with aerodynamic diameter less than 2.5 μm,
PM10 particulate matter with aerodynamic diameter less than 10 μm,
SO2 sulfur dioxide,
NO2 nitrogen dioxide,
CO carbon monoxide,
O3 ozone
Publication bias and sensitivity analysis
Publication bias of studies on PM
10 exposure and stroke hospital admission may exist, since
p values of Begg’s test were less than 0.05. Publication bias of studies was remarkable in association of exposure to PM
2.5 and O
3 and stroke incidence according to funnel plots and Egger’s test. For PM
2.5 and stroke mortality, the
p value of Egger’s test was 0.009, suggesting publication bias may exist. Other publication bias test indicated that no substantial publication bias of studies was observed according to funnel plots, Begg’s test, and Egger’s test (Table
S3, Figure
S19-
34).
Sensitivity analysis showed that the relation of exposure to CO and stroke hospital admission might be influenced by Tian et al.’s study [
10]. And the association between exposure to NO
2 and stroke incidence may be influenced by Dong et al.’s study [
1]. The pooled OR of exposure to air pollution and stroke mortality might be influenced by some studies (PM
2.5: Wang et al.’s study [
33]; O
3: Yin et al.’s study [
37]). We recalculated the pooled OR/HR and 95% CI after removing those studies (Table
S3). Due to limited studies after excluding those studies, the pooled estimated effects of SO
2 and stroke incidence and O
3 and stroke mortality were not recalculated. Other sensitivity analyses indicated that excluding each individual study did not change the results, suggesting the results of the meta-analysis were stable (Table
S4, Figure
S35-
50). Sensitivity analyses by exposure period found that the pooled effect estimates were not changed significantly after excluding the long-term (cohort) studies (Table
S5). Subgroup analysis suggested that both short-term and long-term exposure to air pollution would increase the risk of stroke incidence (PM
2.5, PM
10, and NO
2) and mortality (NO
2) (Table
S6).
Anzeige
Discussion
We conducted a systematic review and meta-analysis of 68 epidemiological studies and performed a comprehensive evaluation on exposure ambient air pollution and stroke, which were conducted from more than 23 million participants. Most studies suggested that exposure to a higher level of air pollution was associated with increased stroke risk. Meta-analysis showed that exposures to air pollutants were associated with increased risk of stroke hospital admission (PM
2.5, PM
10, SO
2, NO
2, CO, and O
3), incidence (PM
2.5, SO
2, and NO
2), and mortality (PM
2.5, PM
10, SO
2, and NO
2). Although the high heterogeneity may reduce the credibility of the pooled evidence to some extent, the large number of studies included and the consistency of the results indicated that our conclusions were credible to some extent.
The positive associations between exposure to PM
2.5, PM
10, SO
2, NO
2, CO, and O
3, and stroke hospital admission were observed in other meta-analysis. Yang et al. meta-analyzed 34 case-crossover and time series studies and reported significant associations for PM
10 (per 10 μg/m
3 increment: RR = 1.007, 95% CI 1.001, 1.013) and O
3 (per 10 ppb increment: RR = 1.036, 95% CI 1.016, 1.056), but non-significant association for PM
2.5, SO
2, NO
2, and CO [
15]. The meta-analysis performed by Yang et al. was not consistent with our current study completely, which might be caused by the different number of the included studies. To our knowledge, more than 16 studies have been published after 2014, and studies included in Yang et al.’s study were mainly conducted in Europe and North America. Data from more recent studies, especially low- and middle-income countries were not considered. Moreover, many studies conducted from the multi-city level and with large sample sizes have been published in recent years, which were more likely to find a significant association between air pollution and stroke hospital admission. For example, Tian et al. performed a time-series of more than 2 million hospital admissions for ischemic stroke in 172 cities in China and suggested that elevated incidence of ischemic stroke hospital admissions was associated with exposure to higher level of PM
2.5 (RR = 1.003, 95% CI 1.002, 1.005, per 10 μg/m
3 increment), SO
2 (RR = 1.013, 95% CI 1.011, 1.017, per 10 μg/m
3 increment), and NO
2 (RR = 1.018, 95% CI 1.015, 1.022, per 10 μg/m
3 increment) [
24].
Three meta-analyses were conducted to examine the association between exposure to particulate matter (PM
2.5 and PM
10) and stroke incidence, whereas no meta-analysis of gas air pollutants was published before the current study. Li et al. performed a meta-analysis to explore the association between PM
10 and stroke incidence in time-series studies and case-crossover studies. These studies indicated that PM
10 was not associated with stroke incidence in the time-series design (HR = 1.002, 95% CI 0.999, 1.005, per 10 μg/m
3 increment), but significantly associated in case-crossover studies (HR = 1.028, 95% CI 1.001, 1.057, per 10 μg/m
3 increment). Meanwhile, PM
2.5 exposure was related to an increased risk of stroke incidence in time-series design (HR = 1.006, 95% CI 1.002, 1.010, per 10 μg/m
3 increment), but no significant association in case-crossover studies (HR = 1.016, 95% CI 0.937, 1.097, per 10 μg/m
3 increment) [
16]. Only 12 studies published before 2010 were included in Li et al.’s study. We updated the literature search up to 2020, which generated more than 10 studies. Moreover, Li et al. separately analyzed the data from time-series and case-crossover studies, which would reduce the number of studies calculated the pooled estimates. These might explain the inconsistency in between our study and Li et al.’s study. Yu et al. updated the literature search before 2012 and identified 19 studies [
19]. Yu et al. found that exposure to PM
10 was associated with an increased risk of stroke incidence (HR = 1.004, 95% CI 1.001, 1.008, per 10 μg/m
3 increment), but exposure to PM
2.5 was not significantly associated with stroke incidence (HR = 0.999, 95% CI 0.994, 1.003, per 10 μg/m
3 increment) [
19]. The results of these published meta-analyses were not exactly the same as our study, which might be due to more than 15 studies published after Yu et al.’s study. Moreover, we conducted a meta-analysis of gas air pollutants and stroke incidence and found that exposure to a higher level of SO
2 and NO
2 was associated with higher risk of stroke incidence, which may fill the gap of meta-analysis of gas air pollutants and stroke incidence. We also found that compared to short-term exposure, long-term exposure to air pollution may be associated with a higher risk of stroke incidence (PM
2.5, PM
10, and NO
2), which may be explained by different pathophysiological pathways.
Studies investigating the association between exposure to air pollution and stroke mortality have been partly analyzed in two meta-analysis [
15,
17]. Yang et al. evaluated the association between all 6 pollutants and suggested that stroke mortality increased 1.34% (95% CI 0.27, 2.42) per 10 μg/m
3 increase in PM
2.5, 0.65% (95% CI 0.54, 0.77) per 10 μg/m
3 increase in PM
10, 2.45% (95% CI 1.83, 3.07) per 10 parts per billion (ppb) increase in SO
2, 7.78% (95% CI 4.49, 11.60) per 1 ppm increase in CO, and 1.50% (95% CI 0.37, 2.63) per 10 ppb increase in NO
2, respectively [
15]. Consistent with Yang et al.’s study, our meta-analysis also indicated that exposure to a higher level of PM
2.5, PM
10, SO
2, and NO
2 was related to higher risk of stroke mortality. No association was observed in both our study and Yang et al.’s study. However, Yang et al. reported a positive association in CO, whereas our study did not, which may be explained by the limited number of included studies. Scheers et al. performed a meta-analysis of exposure to PM
10 and stroke events (mortality and incidence) and suggested that exposure to PM
10 was positively associated with overall stroke events (mortality and incidence) (HR = 1.061, 95% CI 1.018, 1.105), but no significant association were observed in stroke mortality (HR = 1.080, 95% CI 0.992, 1.177) [
17]. Inconsistency of Scheers et al.’s study and current study could be explained that Scheers et al.’s study included the studied estimated exposure to PM
10 from studies using PM
2.5, which may cause estimation bias to some extent.
Anzeige
Although accurate mechanisms of air pollution exposure and stroke remain unclear, several pathways including systemic inflammation, oxidative stress, thrombosis, and vascular endothelial dysfunction have been proposed [
1,
9,
15,
82]. Vascular function injury may be central to mechanisms for air pollution-related stroke, which could lead to raised level of blood pressure and plasma viscosity [
26]. It has been showed that exposure to air pollution was associated with increased thrombosis and vascular endothelial dysfunction by provoking oxidative stress and releasing systemic inflammatory cytokines [
83]. Moreover, evidence also suggested that exposure to air pollution can lead to dysfunction of the autonomic system, which has been found as the major pathway that could result in air pollution-related adverse cardiovascular outcomes, such as stroke [
84]. In addition, stroke status may aggravate the susceptibility of population to air pollution and increase the adverse cardiovascular effects of air pollution circularly [
62].
A major strength of our meta-analysis is that our systematic review and meta-analysis covered six main air pollutants (PM
2.5, PM
10, NO
2, SO
2, CO, O
3) and a rich set of stroke outcomes (hospital admission, incidence, and mortality), which may be difficult to obtain from individual studies or isolated reviews or meta-analyses. However, some limitations should be acknowledged. Firstly, high heterogeneity existed in some meta-analysis, which may be due to different study designs, difference in exposure assessment method and population demographics, and the varied covariable adjustment strategies in different studies. Secondly, our study failed to perform the association between different subtypes of stroke (ischemic stroke, hemorrhagic stroke) and air pollution exposure separately because most included studies (48 out of 68 articles) did not report subtypes of stroke or results of ischemic stroke and hemorrhagic stroke specifically. Finally, the correlation between different air pollutants was not examined in our study because different air pollutants were controlled in different studies, and the results of those studies could not be pooled directly.
Conclusion
Our study demonstrated that exposure to air pollution was positively associated with an increased risk of stroke hospital admission (PM
2.5, PM
10, SO
2, NO
2, CO, and O
3), incidence (PM
2.5, SO
2, and NO
2), and mortality (PM
2.5, PM
10, SO
2, and NO
2). Given the great global burden of stroke and air pollution, our findings could provide some scientific evidence to accurate prevention and treatment of stroke and air pollution exposure.
Acknowledgments
The authors acknowledge all the participants and administrators of this study.
Ethics approval and consent to participate
Not applicable.
Consent for publication
All authors consent for publishing this work.
Competing interests
The authors declare that they have no competing interests.
Open AccessThis article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit
http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (
http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
Publisher’s Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Unsere Produktempfehlungen
e.Med Interdisziplinär
Kombi-Abonnement
Für Ihren Erfolg in Klinik und Praxis - Die beste Hilfe in Ihrem Arbeitsalltag als Mediziner
Mit e.MedInterdisziplinär erhalten Sie Zugang zu allen CME-Fortbildungen und Fachzeitschriften auf SpringerMedizin.de.
Alle e.Med Abos bis 30. April 2021 zum halben Preis!
Association between exposure to ambient air pollution and hospital admission, incidence, and mortality of stroke: an updated systematic review and meta-analysis of more than 23 million participants
Autoren:
Zhiping Niu Feifei Liu Hongmei Yu Shaotang Wu Hao Xiang