Short-term effects of particulate matters on pulse pressure in two general population studies

Investigating the association between ambient particulate matter (PM10) exposure and blood pressure values: Results from the link between the Portuguese Health Examination Survey and air quality data

INTRODUCTION AND OBJECTIVES

High blood pressure (BP) remains a major modifiable cardiovascular (CV) risk factor. Several epidemiologic studies have been performed to assess the association between air pollution exposure and this CV risk factor but results remain inconsistent. This study aims to estimate the effect of short-term PM₁₀ exposure (average previous three-day concentration) on diastolic (DBP) and systolic (SBP) blood pressure values of the resident mainland Portuguese population.

METHODS

Our study was based on available DBP and SBP data from 2272 participants from the first Portuguese Health Examination Survey (INSEF, 2015) living within a 30 km radius of at least one air quality monitoring station, with available measurements of particulate matter with an aerodynamic equivalent diameter ≤10 μm (PM₁₀). We used data from the air quality monitoring network of the Portuguese Environment Agency to obtain the individual allocated PM₁₀ concentrations. Generalized linear models were used to assess the effect of PM₁₀ exposure on DBP and SBP values.

RESULTS

No statistically significant association was found between PM₁₀ exposure and both DBP and SBP values (0.42% DBP change per 10 μg/m³ of PM₁₀ increment (95% confidence interval (CI): -0.85; 1.70) and 0.47% SBP change per 10 μg/m³ of PM₁₀ increment (95% CI: -0.86; 1.79)). Results remain unchanged after restricting the analysis to hypertensive or obese participants or changing the PM₁₀ assessment methodology.

CONCLUSIONS

In view of the PM₁₀ levels observed in 2015, our results suggests that exposure to PM₁₀ concentrations have a small or no effect on the blood pressure values. Other air pollutants and mixtures of pollutants that were not included in our study should considered in future studies.

Synergism of cell adhesion regulatory genes and instant air pollutants on blood pressure elevation

Accumulating evidence suggests that an instant exposure to particulate matter (PM) may elevate blood pressure (BP), where cell-adhesion regulatory genes may be involved in the interplay. However, few studies to date critically examined their interaction, and it remained unclear whether these genes modified the association. To assess the association between instant PM exposure and BP, and to examine whether single-nucleotide polymorphisms (SNPs) mapped in four cell adhesion regulatory genes modify the relationship, a cross-sectional study was performed, based on the baseline of an ongoing family-based cohort in Beijing, China. A total of 4418 persons from 2089 families in Northern China were included in the analysis. Four tagged SNPs in cell adhesion regulatory genes were selected among ZFHX3, CXCL12, RASGRP1 and MIR146A. A generalized additive model (GAM) with a Gaussian link was adopted to estimate the change in blood pressure after instant PM_2.5 or PM₁₀ exposure. A cross-product term of PM_2.5/PM₁₀ and genotype was incorporated into the GAM model to test for interaction. The study observed that an instant exposure to either PM_2.5 or PM₁₀ was found to be associated with elevated systolic blood pressure (SBP). On average, a 10 μg/m³ increase in instant exposure to PM_2.5 and PM₁₀ concentration corresponded to 0.140% (95% CI: 0.014%-0.265%, P = 0.029) and 0.173% (95% CI: 0.080%-0.266%, P < 0.001) higher SBP. However, diastolic blood pressure (DBP) was not elevated as the PM_2.5 or PM₁₀ concentration increased (P > 0.05). A synergetic interaction on SBP was observed between SNPs in four cell adhesion regulatory genes (rs2910164 in MIR146A, rs2297630 in CXCL12, rs7403531 in RASGRP1, and rs7193343 in ZFHX3) and instant PM_2.5 exposure (P_{for interaction} <0.05). Briefly, as carriers of risk alleles in each of these four genes increased, an enhanced association was found between instant PM_2.5 exposure and SBP.

Identification of the susceptible subpopulations for wide pulse pressure under long-term exposure to ambient particulate matters

Wide pulse pressure (WPP) is a preclinical indicator for arterial stiffness and cardiovascular diseases. Long-term exposure to ambient particulate matters (PMs) would increase the risk of WPP. Although reducing pollutants emissions and avoiding outdoor activity during a polluted period are effective ways to blunt the adverse effects. Identifying and protecting the susceptible subpopulation is another crucial way to reduce the disease burdens. Therefore, we aimed to identify the susceptible subpopulations of WPP under long-term exposure to PMs. The WPP was defined as pulse pressure over 60 mmHg. Three-year averages of PMs were estimated using random forest approaches. Associations between WPP and PMs exposure were estimated using generalized propensity score weighted logistic regressions. Demographic, socioeconomic characteristics, health-related behaviors, and hematological biomarkers were collected to detect the modification effects on the WPP-PMs associations. Susceptible subpopulations were defined as those with significantly higher risks of WPP under PMs exposures. The PMs-WPP associations were significant with ORs (95%CI) of 1.126 (1.094, 1.159) for PM₁, 1.174 (1.140, 1.210) for PM_2.5, and 1.111 (1.088, 1.135) for PM₁₀. There were 17 subpopulations more sensitive to WPP under long-term exposure to PMs. The susceptibility was higher in subpopulations with high BMI (Q3-Q4 quartiles), high-intensive physical activity (Q3 or Q4 quartile), insufficient or excessive fruit intake (Q1 or Q5 quartile), insufficient or too long sleep length (<7 or >8 h). Subpopulations with elevated inflammation markers (WBC, LYM, BAS, EOS: Q3-Q4 quartiles) and glucose metabolism indicators (HbA1c, GLU: Q3-Q4 quartiles) were more susceptible. Besides, elder, urban living, low socioeconomic level, and excessive red meat and sodium salt intake were also related to higher susceptibility. Our findings on the susceptibility characteristics would help to develop more targeted disease prevention and therapy strategies. Health resources can be allocated more effectively by putting more consideration to subpopulations with higher susceptibility.

Glucose Metabolic Disorders Enhance Vascular Dysfunction Triggered by Particulate Air Pollution: a Panel Study

BACKGROUND

Vascular dysfunction is a biological pathway whereby particulate matter (PM) exerts deleterious cardiovascular effects. The effects of ambient PM on vascular function in prediabetic individuals are unclear.

METHODS

A panel study recruited 112 Beijing residents with and without prediabetes. Multiple vascular function indices were measured up to 7 times. The associations between vascular function indices and short-term exposure to ambient PM, including fine particulate matter (PM_2.5), ultrafine particles, accumulation mode particles, and black carbon, and the modification of these associations by glucose metabolic status were examined using linear mixed-effects models.

RESULTS

Increases in brachial artery pulse pressure, central aortic pulse pressure, and ejection duration, and decreases in subendocardial viability ratio and reactive hyperemia index were significantly associated with at least one PM pollutant in all participants, indicating increased vascular dysfunction. For example, for an interquartile range increment in 5-day moving average ultrafine particles, brachial artery pulse pressure, and central aortic pulse pressure increased 5.4% (0.8%-10.4%) and 6.2% (1.2%-11.5%), respectively. Additionally, PM-associated changes in vascular function differed according to glucose metabolic status. Among participants with high fasting blood glucose levels (≥6.1 mmol/L), PM exposure was significantly associated with increased brachial artery systolic blood pressure, central aortic systolic blood pressure, brachial artery pulse pressure, central aortic pulse pressure, and augmentation pressure normalized to a heart rate of 75 bpm and decreased subendocardial viability ratio and reactive hyperemia index. Weaker or null associations were observed in the low-fasting blood glucose group.

CONCLUSIONS

Glucose metabolic disorders may exacerbate vascular dysfunction associated with short-term ambient PM exposure.

Acute effects of ambient particulate matter on blood pressure in office workers

Exposure to ambient particulate matter with a diameter of <2.5 μm (PM_2.5) has been linked to increases in blood pressure. The aim of this study was to assess the effects of short-term exposure to PM_2.5 on blood pressure in office workers in Beijing, China. A total of 4801 individuals aged 18-60 years underwent an annual medical examination between 2013 and 2017. Levels of air pollutants were obtained from 35 fixed monitoring stations and correlated with the employment location of each participant to predict personal exposure via kriging interpolation. Linear mixed-effects models were used to estimate the changes in blood pressure associated with PM_2.5 exposure at various lag times. After adjusting for personal characteristics and other potential confounders, each interquartile range increase in PM_2.5 was associated with a 0.413-mmHg (95% confidence interval [CI]: 0.252-0.573), 0.171-mmHg (95% CI: 0.053-0.288), 0.278-mmHg (95% CI: 0.152-0.404), and 0.241-mmHg (95% CI: 0.120-0.362) increase in systolic blood pressure, diastolic blood pressure, pulse pressure, and mean arterial pressure, respectively (p < 0.05). Men, individuals previously diagnosed with hypertension, and subjects working in the northern districts of Beijing had larger changes in blood pressure, and the effect sizes were 0.477-mmHg (95% CI: 0.286-0.669), 0.851-mmHg (95% CI: 0.306-1.397, and 0.672-mmHg (95% CI: 0.405-0.940). The findings suggested that exposure to PM_2.5 had adverse effects on blood pressure, especially among males and hypertensive patients.

Associations of maternal ozone exposures during pregnancy with maternal blood pressure and risk of hypertensive disorders of pregnancy: A birth cohort study in Guangzhou, China

Although studies have assessed the associations of maternal exposure to ozone (O₃) during pregnancy with blood pressure and the risk of hypertensive disorders of pregnancy (HDP), the results were inconsistent. Furthermore, no studies have been conducted in China where the ambient O₃ concentration continuedly increased. The present study aimed to estimate the effects of maternal exposure to O₃ during pregnancy on the HDP risk, systolic blood pressure (SBP), diastolic blood pressure (DBP) and pulse pressure (PP). All participants of pregnant women were selected from the prospective birth cohort study on Prenatal Environments and Offspring Health conducted in Guangzhou, China. A spatiotemporal land-use-regression model was used to estimate individual monthly air pollution exposure from three months before pregnancy to childbirth date. Information on HDP, SBP, DBP and PP was obtained from maternal medical records. A Logistic regression model and a mixed linear model were used to estimate the associations of maternal exposure to O₃ with the risk of HDP and blood pressure (SBP, DBP and PP), respectively. We found significant associations of maternal exposure to O₃ during the third (OR = 1.31, 95%CI: 1.07, 1.60) and the second month (OR = 1.25, 95%CI: 1.02, 1.51) before pregnancy with the risk of HDP. Observed significantly positive associations of O₃ exposures with SBP, DBP and PP during the two months before pregnancy and during the early pregnancy. The peak effects of O₃ exposure on SBP, DBP and PP were respectively observed during the second month of pregnancy (β = 1.07  mmHg, 95%CI: 0.84, 1.31  mmHg), the first month before pregnancy (β = 0.40  mmHg, 95%CI: 0.21, 0.50  mmHg) and the second month of pregnancy (β = 0.78  mmHg, 95%CI: 0.59, 0.97  mmHg). Our results suggest that maternal exposure to O₃ were positively associated with blood pressure and the risk of HDP, and the period from three months before pregnancy to the first trimester might be the critical exposure window.

Effects of short- and long-term exposures to particulate matter on inflammatory marker levels in the general population

The effect of particulate matter (PM) on health increases with exposure duration but the change from short to longer term is not well studied. We examined the exposure to PM smaller 10 μm (PM₁₀) from short to longer duration and their associations with levels of inflammatory markers in the population-based CoLaus cohort in Lausanne, Switzerland. Baseline and follow-up CoLaus data were used to study the associations between PM₁₀ exposure and inflammatory markers, including the high-sensitivity C-reactive protein (CRP), as well as interleukin 1-beta (IL-1β), interleukin 6 (IL-6), and tumor-necrosis-factor alpha (TNF-α) using mixed models. Exposure was determined for each participant's home address from hourly air quality simulations at a 5-m resolution. Short-term exposure intervals were 1 day, 1 week, and 1 month prior to the hospital visit (blood withdrawal); long-term exposure intervals were 3 and 6 months prior to the visit. In most time windows, IL-6, IL-1β, and TNF-α were positively associated with PM₁₀. No significant associations were identified for CRP. Adjusted associations with long-term exposures were stronger and more significant than those for short-term exposures. In stratified models, gender, age, smoking status, and hypertension only led to small modifications in effect estimates, though a few of the estimates for IL-6 and TNF-α became non-significant. In this general adult cohort exposed to relatively low average PM₁₀ levels, clear associations with markers of systemic inflammation were observed. Longer duration of elevated exposure was associated with an exacerbated inflammatory response. This may partially explain the elevated disease risk observed with chronic PM₁₀ exposure. It also suggests that reducing prolonged episodes of high PM exposure may be a strategy to reduce inflammatory risk.

Changing places to study short-term effects of air pollution on cardiovascular health: a panel study

BACKGROUND

Short-term exposure to ambient air pollution triggers acute cardiovascular events. Here, we evaluate the association of exposure to ambient air pollution with two intermediate cardiovascular endpoints: blood pressure and carotid stiffness.

METHODS

In a one-year panel study, we included 20 healthy volunteers (10 male-female couples aged 59-75 years) with air pollution and health parameters measured every two months at their region of residence (Leuven, Belgium) and twice during two ten-day periods in two locations, one with higher (Milan, Italy) and one with lower (Vindeln, Sweden) air pollution levels (220 observations). We measured blood pressure, carotid arterial stiffness, personal exposure to NO₂, and ambient concentrations of PM₁₀, PM_2.5, and NO₂. We used linear mixed models to evaluate the associations between the health outcomes and the air pollutants.

RESULTS

Compared with Leuven, exposure to pollutants was higher in Milan and lower in Vindeln, with the highest contrast for NO₂ (median 20.7 μg/m³ (IQR:7.4) vs 65.1 μg/m³ (9.0) and 4.5 mg/m³ (0.8), respectively). We did not observe significant associations between either systolic or diastolic blood pressure and variations in air pollution. However, we found significant associations between arterial stiffness and 5 day average exposure to the studied pollutants. The strongest associations were observed for PM₁₀ with carotid distensibility (DC) and compliance (CC) coefficients, and the young elastic modulus (YEM): 4.3% (95%CI:7.0;1.5) increase in DC, 4.7% (95%CI:7.1;2.3) increase in CC and 4.2% (95%CI:1.1;7.3) decrease in YEM for each 10 μg/m³ decreases in PM₁₀.

CONCLUSIONS

Our study suggests that short-term exposure to air pollution results in reductions in carotid elasticity among elderly population.

Global association between ambient air pollution and blood pressure: A systematic review and meta-analysis

Although numerous studies have investigated the association of ambient air pollution with hypertension and blood pressure (BP), the results were inconsistent. We performed a comprehensive systematic review and meta-analysis of these studies. Seven international and Chinese databases were searched for studies examining the associations of particulate (diameter<2.5 μm (PM_2.5), 2.5-10 μm (PM_2.5-10) or >10 μm (PM₁₀)) and gaseous (sulfur dioxide (SO₂), nitrogen dioxide (NO₂), nitrogen oxides (NO_x), ozone (O₃), carbon monoxide (CO)) air pollutants with hypertension or BP. Odds ratios (OR), regression coefficients (β) and their 95% confidence intervals were calculated to evaluate the strength of the associations. Subgroup analysis, sensitivity analysis, and meta-regression analysis were also conducted. The overall meta-analysis showed significant associations of long-term exposures to PM_2.5 with hypertension (OR = 1.05), and of PM₁₀, PM_2.5, and NO₂ with DBP (β values: 0.47-0.86 mmHg). In addition, short-term exposures to four (PM₁₀, PM_2.5, SO₂, NO₂), two (PM_2.5 and SO₂), and four air pollutants (PM₁₀, PM_2.5, SO₂, and NO₂), were significantly associated with hypertension (ORs: 1.05-1.10), SBP (β values: 0.53-0.75 mmHg) and DBP (β values: 0.15-0.64 mmHg), respectively. Stratified analyses showed a generally stronger relationship among studies of men, Asians, North Americans, and areas with higher air pollutant levels. In conclusion, our study indicates a positive association between ambient air pollution and increased BP and hypertension. Geographical and socio-demographic factors may modify the pro-hypertensive effects of air pollutants.

Modification of the effects of air pollutants on mortality by temperature: A systematic review and meta-analysis

Temperature extremes and air pollution both pose significant threats to human health, but it remains uncertain whether pollutants' effects on mortality are modified by temperature levels. In this review, we summarized epidemiologic evidence on the modification by temperature of the acute effects of air pollutants on non-accidental and cardiovascular mortality. The EMBASE, PubMed, ProQuest Dissertations and Theses, and Elsevier Science Direct databases were used to identify papers published up to 2nd December 2014. Studies with appropriate design, exposures and outcome indicators, quantitative estimates and high/intermediate quality were included. Twenty-one studies met the inclusion criteria, of which 12 reported the effects of PM₁₀ on mortality modified by temperature, 10 studied O₃, and the rest examined NO₂, SO₂, PM_2.5, PM_10-2.5, CO and black smoke. We divided temperature into low, medium, and high categories as defined in each study. In high temperature days, a 10μg/m³ increment in PM₁₀ concentration corresponded to pooled estimates of 0.78% (95% CI: 0.44%, 1.11%) and 1.28% (0.66%, 1.91%) increase in non-accidental and cardiovascular mortality, both statistically significantly higher than the estimates in medium temperature stratum. Pooled effects of O₃ on non-accidental mortality on low and high temperature days were increases of 0.48% (0.28%, 0.69%) and 0.47% (0.32%, 0.63%) respectively, for 10μg/m³ increase in exposure, both significantly higher than the increase of 0.20% (0.07%, 0.34%) on medium temperature days. The effect of O₃ on cardiovascular mortality was strongest on high temperature days with pooled estimate of 1.63% (1.14%, 2.13%). No significant interactions between SO₂/NO₂ and temperature were detected by meta-analysis. Other pollutants were not analyzed due to the lack of suitable studies. In summary, we observed interactions between high temperature and PM₁₀ and O₃ in the effects on non-accidental and cardiovascular mortality. Low temperature modified the effects of air pollutants but not in a consistent fashion: the effect of PM₁₀ oncardiovascular mortality was diminished but the association between O₃ and non-accidental mortality was strengthened.