The effect of secondary inorganic aerosols, soot and the geographical origin of air mass on acute myocardial infarction hospitalisations in Gothenburg, Sweden during 1985-2010: a case-crossover study

Association between PM10 exposure and risk of myocardial infarction in adults: A systematic review and meta-analysis

BACKGROUND

Air pollution has several negative health effects. Particulate matter (PM) is a pollutant that is often linked to health adversities. PM2.5 (PM with an aerodynamic diameter of ≤2.5μm) exposure has been associated with negative cardiovascular (CV) outcomes. However, the impact of PM10 (PM with an aerodynamic diameter of ≤10μm) exposure is often overlooked due to its limited ability to pass the alveolar barrier. This study aims to assess the association between PM10 exposure and risk of myocardial infarction (MI) amongst adults (≥18 years of age) as this has been poorly studied.

METHODS

The study protocol was published on the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42023409796) on March 31, 2023. Literature searches were conducted on 4 databases (Ovid Medline, Embase, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and Web of Science) on January 17, 2023, for studies looking at associations between PM and MI. English studies from all time periods were assessed. Studies selected for review were time-series, case-crossover, and cohort studies which investigated the risk of MI as an outcome upon PM10 exposure. The quality of evidence was assessed using Cochrane's Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. Data for different risk outcomes (risk ratio (RR), odds ratio (OR), hazard ratio (HR)) and 3 lags was meta-analyzed using an inverse variance statistical analysis using a random effects model. The pooled effect sizes and the 95% confidence intervals (CIs) were reported in forest plots.

RESULTS

Among the 1,099 studies identified, 41 were included for review and 23 were deemed eligible for meta-analysis. Our analysis revealed that there is an increased risk (OR = 1.01; 95% CI:1.00-1.02) of MI with a 10 μg/m3 increase in PM10 after a lag 0 and lag 1 delay.

CONCLUSIONS

Our findings indicate that PM10 exposure is associated with an increased risk of MI. This can aid in informing environmental policy-making, personal-level preventative measures, and global public health action.

Concordance between In Vitro and In Vivo Relative Toxic Potencies of Diesel Exhaust Particles from Different Biodiesel Blends

Diesel exhaust particles (DEPs) contribute to air pollution exposure-related adverse health impacts. Here, we examined in vitro, and in vivo toxicities of DEPs from a Caterpillar C11 heavy-duty diesel engine emissions using ultra-low-sulfur diesel (ULSD) and biodiesel blends (20% v/v) of canola (B20C), soy (B20S), or tallow-waste fry oil (B20T) in ULSD. The in vitro effects of DEPs (DEPULSD, DEPB20C, DEPB20S, and DEPB20T) in exposed mouse monocyte/macrophage cells (J774A.1) were examined by analyzing the cellular cytotoxicity endpoints (CTB, LDH, and ATP) and secreted proteins. The in vivo effects were assessed in BALB/c mice (n = 6/group) exposed to DEPs (250 µg), carbon black (CB), or saline via intratracheal instillation 24 h post-exposure. Bronchoalveolar lavage fluid (BALF) cell counts, cytokines, lung/heart mRNA, and plasma markers were examined. In vitro cytotoxic potencies (e.g., ATP) and secreted TNF-α were positively correlated (p < 0.05) with in vivo inflammatory potency (BALF cytokines, lung/heart mRNA, and plasma markers). Overall, DEPULSD and DEPB20C appeared to be more potent compared to DEPB20S and DEPB20T. These findings suggested that biodiesel blend-derived DEP potencies can be influenced by biodiesel sources, and inflammatory process- was one of the potential underlying toxicity mechanisms. These observations were consistent across in vitro and in vivo exposures, and this work adds value to the health risk analysis of cleaner fuel alternatives.

Case-crossover study for the association between increased hospital admissions for respiratory diseases and the increase in atmospheric PM2.5 and PM2.5-bound trace elements in Pretoria, South Africa

Outdoor PM2.5 was sampled in Pretoria, 18 April 2017 to 28 February 2020. A case-crossover epidemiology study was associated for increased PM2.5 and trace elements with increased hospital admissions for respiratory disorders (J00-J99). The results included a significant increase in hospital admissions, with total PM2.5 of 2.7% (95% CI: 0.6, 4.9) per 10 µg·m-3 increase. For the trace elements, Ca of 4.0% (95% CI: 1.4%-6.8%), Cl of 0.7% (95% CI: 0.0%-1.4%), Fe of 3.3% (95% CI: 0.5%-6.1%), K of 1.8% (95% CI: 0.2-3.5) and Si of 1.3% (95% CI: 0.1%-2.5%). When controlling for PM2.5, only Ca of 3.2% (95% CI: 0.3, 6.1) and within the 0-14 age group by 5.2% (95% CI: 1.5, 9.1). Controlling for a co-pollutant that is highly correlated with PM2.5 does reduce overestimation, but further studies should include deposition rates and parallel sampling analysis.

Source apportionment of fine atmospheric particles in Bloemfontein, South Africa, using positive matrix factorization

Air pollution is of major health and environmental concern globally and in South Africa. Studies on the sources of PM2.5 air pollution in low- and middle-income countries such as South Africa are limited. This study aimed to identify local and distant sources of PM2.5 pollution in Bloemfontein. PM2.5 samples were collected from June 16, 2020 to August 18, 2021. Trace element concentrations were determined by EDXRF spectroscopy. By use of the US EPA PMF 5.0 program, local sources were determined to be combustion/wood burning (49%), industry (22%), soil dust (10%), base metal/pyrometallurgical and traffic (9.6%) and water treatment/industry (9.4%). The HYSPLIT program was applied to determine distant PM2.5 source areas and the following clusters were identified: Mpumalanga province (52%), Northern Cape province (35%), Indian Ocean (8%) and Atlantic Ocean (6%). The majority of the air was found to come from the Mpumalanga province in the north-east, while the majority of local sources are ascribed to combustion/wood burning. Results from this study can be used to develop an Air Quality Management Plan for Bloemfontein.

Associations between short-term exposure to fine particulate matter and acute myocardial infarction: A case-crossover study

BACKGROUND

Previous studies evaluated the impact of particle matters (PM) on the risk of acute myocardial infarction (AMI) based on local registries.

HYPOTHESIS

This study aimed to evaluate possible short term effect of air pollutants on occurrence of AMI based on a specific case report sheet that was designed for this purpose.

METHODS

AMI was documented among 982 patients who referred to the emergency departments in Tehran, Iran, between July 2017 to March 2019. For each patient, case period was defined as 24 hour period preceding the time of emergency admission and referent periods were defined as the corresponding time in 1, 2, and 3 weeks before the admission. The associations of particulate matter with an aerodynamic diameter ≤2.5 μm (PM2 .5 ) and particulate matter with an aerodynamic diameter ≤10 μm (PM10 ) with AMI were analyzed using conditional logistic regression in a case-crossover design.

RESULT

Increase in PM2.5 and PM10 was significantly associated with the occurrence of AMI with and without adjustment for the temperature and humidity. In the adjusted model each 10 μg/m3 increase of PM10 and PM2.5 in case periods was significantly associated with increase myocardial infarction events (95% CI = 1.041-1.099, OR = 1.069 and 95% CI = 1.073-1.196, and OR = 1.133, respectively). Subgroup analysis showed that increase in PM10 did not increase AMI events in diabetic subgroup, but in all other subgroups PM10 and PM2 .5 concentration showed positive associations with increased AMI events.

CONCLUSION

Acute exposure to ambient air pollution was associated with increased risk of AMI irrespective of temperature and humidity.

Regional air pollution severity affects the incidence of acute myocardial infarction triggered by short-term pollutant exposure: a time-stratified case-crossover analysis

Long-term exposure to air pollution results in a high incidence of cardiovascular disease. Many studies have found that short-term exposure to air pollution can trigger acute myocardial infarction. This study aims to determine whether results in areas with different levels of severity of air pollution are similar. The study design is a time-stratified case-crossover analysis. This was a retrospective study based on hospital medical records. The study period was since 1 January 2017 to 31 December 2018. Research data were collected from Taoyuan Hospital, located in an area with low severity of pollution, and Taichung Hospital, located in an area with high severity of pollution. The correlation between short-term air pollution exposure and acute myocardial infarction was analyzed. The correlation between short-term exposure to ambient air pollutants and acute myocardial infarction was not significant for the cases collected from Taoyuan Hospital (PM_2.5 OR: 1.006 and 95% CI: 0.995-1.017; PM₁₀ OR: 0.996 and 95% CI: 0.988-1.003). However, for the cases collected from Taichung Hospital, short-term exposure to ambient PM_2.5 (odds ratio: 1.021; 95% confidence interval: 1.002-1.040) and PM₁₀ (odds ratio: 1.010; 95% confidence interval: 1.001-1.020) resulted in high incidence of acute myocardial infarction. Short-term pollutant exposure will increase the incidence of acute myocardial infarction based on the severity of regional air pollution. In addition to addressing traditional cardiovascular disease risk factors, the government must formulate relevant policies for reducing air pollution and the resulting hazards to citizens' health.

Cold Climate Impact on Air-Pollution-Related Health Outcomes: A Scoping Review

In cold temperatures, vehicles idle more, have high cold-start emissions including greenhouse gases, and have less effective exhaust filtration systems, which can cause up to ten-fold more harmful vehicular emissions. Only a few vehicle technologies have been tested for emissions below -7 °C (20 °F). Four-hundred-million people living in cities with sub-zero temperatures may be impacted. We conducted a scoping review to identify the existing knowledge about air-pollution-related health outcomes in a cold climate, and pinpoint any research gaps. Of 1019 papers identified, 76 were selected for review. The papers described short-term health impacts associated with air pollutants. However, most papers removed the possible direct effect of temperature on pollution and health by adjusting for temperature. Only eight papers formally explored the modifying effect of temperatures. Five studies identified how extreme cold and warm temperatures aggravated mortality/morbidity associated with ozone, particles, and carbon-monoxide. The other three found no health associations with tested pollutants and temperature. Additionally, in most papers, emissions could not be attributed solely to traffic. In conclusion, evidence on the relationship between cold temperatures, traffic-related pollution, and related health outcomes is lacking. Therefore, targeted research is required to guide vehicle regulations, assess extreme weather-related risks in the context of climate change, and inform public health interventions.

Source apportionment of fine atmospheric particles using positive matrix factorization in Pretoria, South Africa

In Pretoria South Africa, we looked into the origins of fine particulate matter (PM_2.5), based on 1-year sampling campaign carried out between April 18, 2017, and April 17, 2018. The average PM_2.5 concentration was 21.1 ± 15.0 µg/m³ (range 0.7-66.8 µg/m³), with winter being the highest and summer being the lowest. The XEPOS 5 energy dispersive X-ray fluorescence (EDXRF) spectroscopy was used for elemental analysis, and the US EPA PMF 5.0 program was used for source apportionment. The sources identified include fossil fuel combustion, soil dust, secondary sulphur, vehicle exhaust, road traffic, base metal/pyrometallurgical, and coal burning. Coal burning and secondary sulphur were significantly higher in winter and contributed more than 50% of PM_2.5 sources. The HYSPLIT model was used to calculate the air mass trajectories (version 4.9). During the 1-year research cycle, five transportation clusters were established: North Limpopo (NLP), Eastern Inland (EI), Short-Indian Ocean (SIO), Long-Indian Ocean (LIO), and South Westerly-Atlantic Ocean (SWA). Local and transboundary origin accounted for 85%, while 15% were long-range transport. Due to various anthropogenic activities such as biomass burning and coal mining, NLP clusters were the key source of emissions adding to the city's PM rate. In Pretoria, the main possible source regions of PM_2.5 were discovered to be NLP and EI. Effective control strategies designed at reducing secondary sulphur, coal burning, and fossil fuel combustion emissions at Southern African level and local combustion sources would be an important measure to combat the reduction of ambient PM_2.5 pollution in Pretoria.

Concentration-response relationships between hourly particulate matter and ischemic events: A case-crossover analysis of effect modification by season and air-mass origin

Most studies linking cardiovascular disease with particulate matter (PM) exposures have focused on total mass concentrations, regardless of their origin. However, the origin of an air mass is inherently linked to particle composition and possible toxicity. We examine how the concentration-response relation between hourly PM exposure and ischemic events is modified by air-mass origin and season. Using telemedicine data, we conducted a case-crossover study of 1855 confirmed ischemic cardiac events in Israel (2005-2013). Based on measurements at three fixed-sites in Tel Aviv and Haifa, ambient PM with diameter < 2.5 μm (PM_2.5) and 2.5-10 μm (PM_10-2.5) concentrations during the hours before event onset were compared with matched control periods using conditional logistic regression that allowed for non-linearity. We also examined effect modification of these associations based on the geographical origin of each air mass by season. Independent of the geographical origin of the air mass, we observed concentration-response curves that were supralinear. For example, the overall odds ratios (ORs) of ischemic events for an increase of 10-μg/m³ in the 2-h average of PM_10-2.5 were 1.08 (95% confidence interval (CI): 1.03-1.14) and 1.00 (0.99-1.01) at the median (17.8 μg/m³) and 95th percentile (82.3 μg/m³) values, respectively. Associations were strongest at low levels of PM_10-2.5 when air comes from central Europe in the summer (OR: 1.27; 95% CI: 1.06, 1.52). Our study demonstrates that hourly associations between PM_2.5 and PM_10-2.5 and ischemic cardiac events are supralinear during diverse pollution conditions in a single population that experiences a wide range of exposure levels.

PM2.5 chemical composition and geographical origin of air masses in Cape Town, South Africa

PM2.5 in the indoor and outdoor environment has been linked in epidemiology studies to the symptoms, hospital admissions and development of numerous health outcomes including death. The study was conducted during April 2017 and April 2018. PM2.5 samples were collected over 24 h and every third day. The mean PM2.5 level was 13.4 μg m-3 (range: 1.17-39.1 μg m-3). PM2.5 levels exceeded the daily World Health Organization air quality guideline (25 μg m-3) on 14 occasions. The mean soot level was 1.38 m-1 × 10-5 (range: 0 to 5.38 m-1 × 10-5). Cl-, NO3 -, SO4 2-, Al, Ca, Fe, Mg, Na and Zn were detected in the PM2.5 samples. The geographical origin of air masses that passed Cape Town was estimated using the Hybrid Single Particle Lagrangian Integrated Trajectory software. Four air masses were identified in the cluster analysis: Atlantic-Ocean-WSW, Atlantic-Ocean-SW, Atlantic-Ocean-SSW and Indian-Ocean. The population of Cape Town may experience various health outcomes from the outdoor exposure to PM2.5 and the chemical composition of PM2.5.

Association between PM2.5 and risk of hospitalization for myocardial infarction: a systematic review and a meta-analysis

Background

It is generally assumed that there have been mixed results in the literature regarding the association between ambient particulate matter (PM) and myocardial infarction (MI). The aim of this meta-analysis was to explore the rate of short-term exposure PM with aerodynamic diameters ≤2.5 μm (PM_2.5) and examine its potential effect(s) on the risk of MI.

Methods

A systematic search was conducted on databases like PubMed, Scopus, Web of Science, and Embase with components: “air pollution” and “myocardial infarction”. The summary relative risk (RR) and 95% confidence intervals (95%CI) were also calculated to assess the association between the PM_2.5 and MI.

Results

Twenty-six published studies were ultimately identified as eligible candidates for the meta-analysis of MI until Jun 1, 2018. The results illustrated that a 10-μg/m 3 increase in PM_2.5 was associated with the risk of MI (RR = 1.02; 95% CI 1.01–1.03; P ≤ 0.0001). The heterogeneity of the studies was assessed through a random-effects model with p < 0.0001 and the I² was 69.52%, indicating a moderate degree of heterogeneity. We also conducted subgroup analyses including study quality, study design, and study period. Accordingly, it was found that subgroups time series study design and high study period could substantially decrease heterogeneity (I² = 41.61, 41.78).

Conclusions

This meta-analysis indicated that exposure – response between PM_2.5 and MI. It is vital decision makers implement effective strategies to help improve air pollution, especially in developing countries or prevent exposure to PM_2.5 to protect human health.

Evaluation of a meta-analysis of air quality and heart attacks, a case study

It is generally acknowledged that claims from observational studies often fail to replicate. An exploratory study was undertaken to assess the reliability of base studies used in meta-analysis of short-term air quality-myocardial infarction risk and to judge the reliability of statistical evidence from meta-analysis that uses data from observational studies. A highly cited meta-analysis paper examining whether short-term air quality exposure triggers myocardial infarction was evaluated as a case study. The paper considered six air quality components - carbon monoxide, nitrogen dioxide, sulphur dioxide, particulate matter 10 μm and 2.5 μm in diameter (PM10 and PM2.5), and ozone. The number of possible questions and statistical models at issue in each of 34 base papers used were estimated and p-value plots for each of the air components were constructed to evaluate the effect heterogeneity of p-values used from the base papers. Analysis search spaces (number of statistical tests possible) in the base papers were large, median = 12,288 (interquartile range = 2496 - 58,368), in comparison to actual statistical test results presented. Statistical test results taken from the base papers may not provide unbiased measures of effect for meta-analysis. Shapes of p-value plots for the six air components were consistent with the possibility of analysis manipulation to obtain small p-values in several base papers. Results suggest the appearance of heterogeneous, researcher-generated p-values used in the meta-analysis rather than unbiased evidence of real effects for air quality. We conclude that this meta-analysis does not provide reliable evidence for an association of air quality components with myocardial risk.

Short-term effects of fine particulate matter on acute myocardial infraction mortality and years of life lost: A time series study in Hong Kong

Previous studies have applied years of life lost (YLL) as a complementary indicator to assess the short-term effect of the air pollution on the health burden from all-cause mortality, but sparsely focused on individual diseases such as acute myocardial infraction (AMI). In this study, we aimed to conduct a time-series analysis to evaluate short-term effects of fine particulate matter (PM_2.5) on mortality and YLL from AMI in Hong Kong from 2011 to 2015, and explore the potential effect modifiers including sex and age by subgroup analysis. We applied generalized additive Poisson and Gaussian regression model for daily death count and YLL, respectively. We found that 10μg/m³ increment in concentration of PM_2.5 lasting for two days (lag₀₁) was associated with a 2.35% (95% CI 0.38% to 4.36%) increase in daily mortality count and a 1.69 (95% CI 0.01 to 3.37) years increase in YLL from AMI. The association between PM_2.5 and AMI mortality count was stronger among women and older people than men and young people, respectively. We concluded that acute exposure to PM_2.5 may increase the risk of mortality and YLL from AMI in Hong Kong and this effect can be modified by age and gender. These findings add to the evidence base for public health policy formulation and resource allocation.

Long-range transport clusters and positive matrix factorization source apportionment for investigating transboundary PM2.5 in Gothenburg, Sweden

Source apportionment studies of particulate matter are common and have been performed either as source region analyses using air mass back trajectories or by source type using source apportionment techniques. By combining the two approaches, it is possible to estimate the relative importance of emitters in different regions. PM_2.5 samples were collected in Gothenburg between September 2008 and September 2009. The mean daily PM_2.5 level was 6.1 μg m^-3 (range 0.79-30.91 μg m^-3). Elemental analyses were done using Energy dispersive X-ray fluorescence (EDXRF) spectroscopy. Source apportionment was carried out using the US EPA PMF 5.0 software. The sources long-range transport (LRT), LRT-Pb (lead-containing LRT), ship emissions, combustion, marine, and resuspension were identified. Air mass trajectories were estimated using HYSPLIT model (version 4.9). Six transport clusters were identified: South Scandinavia 21%, North Scandinavia 11%, Baltic Sea 8%, Eastern Europe 6%, UK/North Sea/Denmark 25%, and North Atlantic Ocean 30%. LRT was the major contributor to PM_2.5 levels across all six transport clusters (48%) followed by ship emissions (20%) and combustion (19%). The transport cluster associated with the highest PM_2.5 levels was Eastern Europe followed by South Scandinavia, UK/North Sea/Denmark, and Baltic Sea. After considering the frequency of the transport clusters, the transport clusters associated with the highest PM_2.5 levels were UK-NorthS-DK, S-Scandic, and N-Atlantic, while Eastern Europe only contributed 9% towards PM_2.5 levels. Abatement strategies aimed at reductions of ship emissions, industry emissions, and road traffic emissions on an European level and local combustion sources on a city-scale level would be the two most effective directions for reducing ambient PM_2.5 in Gothenburg.

Short-term effects of atmospheric particulate matter on myocardial infarction: a cumulative meta-analysis

Atmospheric particulate matter (PM) is hypothesized to increase the risk of myocardial infarction (MI). However, the epidemiological evidence is inconsistent. We identified 33 studies with more than 4 million MI patients and applied meta-analysis and meta-regression to assess the available evidence. Twenty-five studies presented the effects of the PM level on hospitalization for MI patients, while eight studies showed the effects on mortality. An increase in PM10 was associated with hospitalization and mortality in myocardial infarction patients (RR per 10 μg/m(3) = 1.011, 95% CI 1.006-1.016; RR per 10 μg/m(3) = 1.008, 95 % CI 1.004-1.012, respectively); PM2.5 also increased the risk of hospitalization and mortality in MI patients (RR per 10 μg/m(3) = 1.024, 95% CI 1.007-1.041 for hospitalization and RR per 10 μg/m(3) = 1.012, 95% CI 1.010-1.015 for mortality). The results of the cumulative meta-analysis indicated that PM10 and PM2.5 were associated with myocardial infarction with the addition of new studies each year. In conclusion, short-term exposure to high PM10 and PM2.5 levels revealed to increase risk of hospitalization and mortality for myocardial infarction. Policy support of pollution control and individual protection was strongly recommended.

Comparison of transient associations of air pollution and AMI hospitalisation in two cities of Alberta, Canada, using a case-crossover design

OBJECTIVE

To investigate reproducibility of outcomes for short-term associations between ambient air pollutants and acute myocardial infarction (AMI) hospitalisation in 2 urban populations.

DESIGN

Using a time-stratified design, we conducted independent case-crossover studies of AMI hospitalisation events over the period 1999-2010 in the geographically close and demographically similar cities of Calgary and Edmonton, Alberta, Canada. Patients with his/her first AMI hospitalisation event were linked with air pollution data from the National Ambient Pollution Surveillance database and meteorological data from the National Climatic Data Center database. Patients were further divided into subgroups to examine adjusted pollution effects. Effects of pollution levels with 0-3-day lag were modelled using conditional logistic regression and adjusted for daily average ambient temperature, dew point temperature and wind speed.

SETTING

Population-based studies in Calgary/Edmonton.

PARTICIPANTS

12,066/10,562 first-time AMI hospitalisations in Calgary/Edmonton.

MAIN OUTCOME MEASURES

Association (adjusted OR) between daily ambient air pollution levels and hospitalisation for AMI.

RESULTS

Among 600 potential air pollution effect variables investigated for the Calgary (Edmonton) population, only 1.17% (0.67%) was statistically significant by using the traditional 5% criterion. None of the effect variables were reproduced in the 2 cities, despite their geographic closeness (within 300 km of each other), and demographic and air pollution similarities.

CONCLUSIONS

Comparison of independent investigations of the effect of air pollution on risk of AMI hospitalisation in Calgary and Edmonton, Alberta, indicated that none of the air pollutants investigated-CO, NO, NO2, O3 and particulate matter (PM2.5)-showed consistent positive associations with increased risk of AMI hospitalisation.

Short-term exposure to particulate air pollution and risk of myocardial infarction: a systematic review and meta-analysis

A growing number of studies have associated short-term exposure to ambient particulate matter air pollution (PM) and risk of specific cardiovascular events, just as myocardial infarction (MI). However, the results of the recent studies were inconsistent; therefore, a systematic review and meta-analysis was performed. To synthetically quantify the association between short-term exposure to PM and risk of MI, a meta-analysis was conducted to combine the estimates of effect for a relationship between short-term exposure to PM10, PM2.5 (particulate matter ≤ 10 μm, 2.5 μm in diameter) and risk of MI. Electronic database searches for all relevant published studies were updated in January 2015. And, a random-effects model was performed to estimate pooled relative risk (RR) and 95 % confidence intervals (95 % CI). Thirty-one published observational epidemiological studies were identified. Risk of MI was significantly associated with per 10 μg/m(3) increment in PM10 (OR = 1.005; 95 % CI 1.001-1.008) and PM2.5 (OR = 1.022; 95 % CI 1.015-1.030). The risk of PM2.5 exposure was relatively greater than PM10. In the subgroup analysis by study design, location, quality score, and lag exposure, the results were basically consistent with the former overall results in PM2.5 but slightly changed in PM10. Short-term exposure to particulate matter (PM2.5, PM10) was a risk factor for MI, and the results further confirmed the discovery in the previous meta-analysis.