Air pollution and stroke - an overview of the evidence base

Time-Series analysis of short-term exposure to air pollutants and daily hospital admissions for stroke in Tabriz, Iran

BACKGROUND

Air pollution is considered one of the risk factors for stroke prevalence in the long term and incidence in the short term. Tabriz is one of the most important industrial cities in Iran. Hence, air pollution has always been one of the main concerns in environmental health in the region.

METHOD

The patient data were retrieved from electronic health records of the primary tertiary hospital of the city (Imam Reza Hospital). Air pollution data was obtained from the Environmental Protection Agency and is generated by 8 sensor stations spread across the city. Average daily values were calculated for CO, NO, NO, NOx, O3, SO2, PM2.5, and PM10 from hourly measurement data. Autoregressive integrated moving average (ARIMA-X) model with 3 lag days was developed to assess the correlation.

RESULTS

Air pollutants and hospital admission data were collected for 1821 day and includes 4865 stroke cases. our analysis showed no statistically significant association between the daily concentrations of CO (p = 0.41), NOx (p = 0.96), O3 (p = 0.65), SO2 (p = 0.91), PM2.5 (p = 0.44), and PM10 (p = 0.36). Only the binary COVID variable which was used to distinguish between COVID-19 era and other days, was significant (p value = 0.042). The goodness of fit measures, Root Mean Squared Error (RMSE), and Median Absolute Error (MAE) were 1.81 and 1.19, respectively.

CONCLUSION

In contrast to previous reports on the subject, we did not find any pollutant significantly associated with an increased number of stroke patients.

Short-Term Exposure to Air Pollution and the Incidence and Mortality of Stroke: A Meta-Analysis

BACKGROUND

The relationship between short-term exposure to various air pollutants [particulate matter <10 μm (PM 10 ), particulate matter <2.5 μm (PM 2.5 ), nitrogen dioxide (NO 2 ), sulfur dioxide (SO 2 ), carbon monoxide, and ozone (O 3 )] and the incidence and mortality of stroke remain unclear.

REVIEW SUMMARY

We conducted a comprehensive search across databases, including PubMed, Web of Science, and others. A random-effects model was employed to estimate the odds ratios (OR) and their 95% CIs. Short-term exposure to PM 10 , PM 2.5 , NO 2 , SO 2 , and O 3 was associated with increased stroke incidence [per 10 μg/m 3 increase in PM 2.5 : OR = 1.005 (95% CI: 1.004-1.007), per 10 μg/m 3 increase in PM 10 : OR = 1.006 (95% CI: 1.004-1.009), per 10 μg/m 3 increase in SO 2 : OR = 1.034 (95% CI: 1.020-1.048), per 10 μg/m 3 increase in NO 2 : OR = 1.029 (95% CI: 1.015-1.043), and O 3 for per 10 μg/m 3 increase: OR: 1.006 (95% CI: 1.004-1.007)]. In addition, short-term exposure to PM 2.5 , PM 10 , SO 2, and NO 2 was correlated with increased mortality from stroke [per 10 μg/m 3 increase in PM 2.5 : OR = 1.010 (95% CI: 1.006-1.013), per 10 μg/m 3 increase in PM 10 : OR = 1.004 (95% CI: 1.003-1.006), per 10 μg/m 3 increase in SO 2 : OR = 1.013 (95% CI: 1.007-1.019) and per 10 μg/m 3 increase in NO 2 : OR = 1.012 (95% CI: 1.008-1.015)].

CONCLUSION

Reducing outdoor air pollutant levels may yield a favorable outcome in reducing the incidence and mortality associated with strokes.

Ambient Air Pollution and Stroke: An Updated Review

Despite recent advances in treatment and prevention, stroke remains a leading cause of morbidity and mortality. There is a critical need to identify novel modifiable risk factors for disease, including environmental agents. A body of evidence has accumulated suggesting that elevated levels of ambient air pollutants may not only trigger cerebrovascular events in susceptible people (short-term exposures) but also increase the risk of future events (long-term average exposures). This review assesses the updated evidence for both short and long-term exposure to ambient air pollution as a risk factor for stroke incidence and outcomes. It discusses the potential pathophysiologic mechanisms and makes recommendations to mitigate exposure on a personal and community level. The evidence indicates that reduction in air pollutant concentrations represent a significant population-level opportunity to reduce risk of cerebrovascular disease.

Air Pollution and Its Devastating Effects on the Central Nervous System

Air pollution is a real public health problem, it being one of the five most common causes of mortality in developing countries. However, pollution studies have focused on the cardiovascular and pulmonary systems in recent decades. Recently, researchers have moved towards a new direction, tracing a direct link between pollution and stroke. Stroke has many known risk factors such as smoking, a sedentary lifestyle, and hypertension. Pollution is universally widespread, already a matter of public interest, so that, although intuitive, it is difficult to connect the two. The particles found in the air that we breathe, regardless of their origin, can attack the body in different ways, causing inflammation, and triggering a true cascade of phenomena that end up attacking the central nervous system and other organs. This article tries to explain the series of phenomena that determine the harmful effect of particles present in the air, with an increased focus on the central nervous system and especially on strokes. A deeper understanding of these phenomena helps in guiding future studies and finding viable solutions to protect people at risk.

Short-, Mid-, and Long-Term Associations Between PM2.5 and Stroke Incidence in Taiwan

OBJECTIVE

To investigate the association between the risk of stroke and exposure to particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5) over various exposure periods.

METHODS

This was a nationwide population-based case-control study in which 10,035 incident patients with a primary diagnosis of ischemic stroke each were matched with two randomly selected controls for sex, age, Charlson Comorbidity Index, year of stroke diagnosis, and level of urbanization. Multiple logistic models adjusted for potential confounders were used to assess the association of PM2.5 with ischemic stroke incidence.

RESULTS

There were significant short-term, medium-term, and long-term relationships between PM2.5 exposure and ischemic stroke incidence.

CONCLUSIONS

This study supports existing evidence that PM2.5 should be considered a risk factor for ischemic stroke.

Atmospheric variables and subarachnoid hemorrhage: narrative review

Background

Stroke is a neurological emergency that tends to be the first cause of death in many countries. Atmospheric variables are strongly associated with stroke, in which subarachnoid hemorrhage (SAH) has been associated in many studies to meteorological risk factors such as air pollution, air pressure, weather changes, and ambient temperature. These characteristics may influence the brain circulation and cause SAH, being diagnosed as idiopathic SAH or SAH with unknown cause.

Objective

The main objective of this review is to present the most relevant meteorological risk factors that may develop subarachnoid hemorrhage according to the current evidence that supports the strong association.

Conclusion

Brain vessel circulation may be influenced by atmospheric variables such as air pollution and weather changes, generating intrinsic changes in the intima of the vessels which leads to vasospasm and with comorbidities associated may develop SAH.

Multiple performances and paradoxical effects of China's vehicle emission reduction policy

As the living standards of urban residents in China continue to improve, the number of motor vehicle trips is increasing, thus aggravating air pollution. Such pollution causes great harm to human health and the global environment. Using a system dynamics approach, this study analyzed the effect of implementation mode on China's air pollution charging fee (APCF) policy and identified potentially negative medium- and long-term effects. The results indicated that the APCF policy has a dual effect under the single-charge mode (i.e., fees are charged on a daily basis). On the one hand, it has multiple effects of reducing emissions, relieving traffic congestion, and improving the happiness index. On the other hand, the higher the charge, the stronger the trip demand (possibly due to the sunk-cost fallacy and loss-aversion effect), which encourages motorists to weaken the cost of losses (i.e., from air pollution fees) by increasing the number of trips per day to seek short-term psychological balance, regardless of the extra costs and the amount of pollution generated. It was also found that APCF implementation mode significantly affected passenger car trips but not truck trips (perhaps because truck trips are mainly based on the demand of supply, and the daily number of trips is relatively stable). Overall, as APCF increases, it can have some paradoxical long-term effects on emissions, congestion, the happiness index, and road bearing capacity. This study's findings can help the Chinese government improve and optimize its long-term air pollution control strategies.

Neurological disorders vis-à-vis climate change

Climate change is one of the biggest challenges humanity is facing in the 21st century. Two recognized sequelae of climate change are global warming and air pollution. The gradual increase in ambient temperature, coupled with elevated pollution levels have a devastating effect on our health, potentially contributing to the increased rate and severity of numerous neurological disorders. The main aim of this review paper is to shed some light on the association between the phenomena of global warming and air pollution, and two of the most common and debilitating neurological conditions: stroke and neurodegenerative disorders. Extreme ambient temperatures induce neurological impairment and increase stroke incidence and mortality. Global warming does not participate in the etiology of neurodegenerative disorders, but it exacerbates symptoms of dementia, Alzheimer's disease (AD) and Parkinson's Disease (PD). A very close link exists between accumulated levels of air pollutants (principally particulate matter), and the incidence of ischemic rather than hemorrhagic strokes. People exposed to air pollutants have a higher risk of developing dementia and AD, but not PD. Oxidative stress, changes in cardiovascular and cerebrovascular haemodynamics, excitotoxicity, microglial activation, and cellular apoptosis, all play a central role in the overlap of the effect of climate change on neurological disorders. The complex interactions between global warming and air pollution, and their intricate effect on the nervous system, imply that future policies aimed to mitigate climate change must address these two challenges in unison.

Spatial analysis of service areas for stroke centers in a city with high traffic congestion

The effect that traffic congestion has on the service areas of stroke centers has received scarce attention. We aimed to determine the effect of traffic conditions on the characteristics of service areas of stroke centers in Bogotá, Colombia. Using a webservice, we sampled travel times from a set of census blocks to medical centers offering stroke management in the city. We obtained 179.340 transport times under different conditions. The size of service areas was reduced significantly with congestion (up to 94.83%). Overlap in the locations of centers led to large areas covered by only five centers. We identified areas with transport times to the closest center consistently exceeding 30-minutes to 1-hour in the west and south-west. Traffic conditions in Bogotá significantly affect service areas of centers capable of offering comprehensive stroke care. Spatial overlap of centers led to small catchment areas.

Mitigation strategies for reducing air pollution

Today, it is increasingly recognized that air pollution hurts human health. Consequently, efficient mitigation strategies need to be implemented for substantial environmental and health co-benefits. A valid approach to reducing the air pollution effects on the environment and human health is proposed. Specific guidelines have been elucidated by differentiating them on the base of the final stakeholders (citizens, enterprises, and public authorities), of the emission sources (transport, household energy, industry, and energy generation sector, agriculture, and shipping area), and of the field of implementation (urban and extra-urban context). This paper can provide useful information for governments for the implementation of a strategic plan focused on emphasizing multi-pollutant emission reductions and overall air pollution-related risk.

Short-term effect of PM1 on hospital admission for ischemic stroke: A multi-city case-crossover study in China

This study aims to examine the association between short-term exposures to PM₁, PM_2.5 and PM₁₀ (particulate matter with aerodynamic diameters ≤1 μm, ≤2.5 μm and ≤10 μm, respectively) and hospital admission for ischemic stroke in China. Daily counts of hospital admission for ischemic stroke were collected in 5 hospitals in China during November 2013 to October 2015. Daily concentrations of PM₁, PM_2.5 and PM₁₀ were collected in 5 cities where the hospitals were located. A time-stratified case-crossover design was used to examine the hospital-specific PM-ischemic stroke association after controlling for potential confounders. Then the effect estimates were pooled using a random-effect meta-analysis. A total of 68,122 hospital admissions for ischemic stroke were identified from 5 hospitals during the study period. The pooled results showed that exposures to PM₁, PM_2.5 and PM₁₀ were significantly associated with increased hospital admission for ischemic stroke on the current day and previous 1 day. The RRs (relative risk associated with per 10 μg/m³ increase in each pollutant) and 95%CIs (confidence intervals) for the cumulative effects of PM₁, PM_2.5 and PM₁₀ on ischemic stroke during lag 0-1 days were 1.014 (1.005, 1.0023), 1.007 (1.000, 1.014) and 1.005 (1.001, 1.009), respectively. In total, 3.5%, 3.6% and 4.1% of hospital admissions for ischemic stroke could be attributable to PM₁, PM_2.5 and PM₁₀, respectively. Exposures to ambient PM₁, PM_2.5 and PM₁₀ pollution showed acute adverse effects on hospital admission for ischemic stroke. The health effects of PM₁ should be considered by policy-makers.

Effect of air pollution on hospitalization for acute exacerbation of chronic obstructive pulmonary disease, stroke, and myocardial infarction

This study aims to analyze the acute effects of PM_2.5, PM₁₀, SO₂, NO₂, and O₃ on hospitalizations for acute exacerbation of chronic obstructive pulmonary disease (AECOPD), stroke, and myocardial infarction (MI) from 2014 to 2017 in Shenyang, China. Hospitalization records for AECOPD (17,655), stroke (276,736) and MI (26,235) and air pollutions concentration data (PM_2.5, PM₁₀, SO₂, NO₂, and O₃) were collected. A generalized additive model (GAM) was utilized to determine the impact of air pollutants on the relative risk (RR) of hospitalization for AECOPD, stroke, and MI. Stratified analysis for AECOPD was based on gender and age. It was based on gender, age, hypertension, and diabetes for stroke, and for MI it was based on gender, age, and coronary atherosclerosis. The lag effect for AECOPD in terms of gender analysis occurred at lag3-lag5. The hospitalization risk for stroke with hypertension due to SO₂ and NO₂ was greater than that of stroke without hypertension. The risk of hospitalization for stroke with hypertension as a comorbidity due to O₃ was lower than without hypertension. The risk of hospitalization for MI combined with coronary atherosclerosis due to PM_2.5, PM₁₀, or NO₂ was higher than that of hospitalizations for MI without coronary atherosclerosis. Air pollution increased the rate of hospitalization for AECOPD. SO₂ and O₃ appeared protective for stroke patients with coronary atherosclerosis. PM_2.5, PM₁₀, and NO₂ had no influence on total hospitalization for myocardial infarction.

A time series analysis of the relationship between apparent temperature, air pollutants and ischemic stroke in Madrid, Spain

The understanding of the role of environment on the pathogenesis of stroke is gaining importance in the context of climate change. This study analyzes the temporal pattern of ischemic stroke (IS) in Madrid, Spain, during a 13-year period (2001-2013), and the relationship between ischemic stroke (admissions and deaths) incidence and environmental factors on a daily scale by using a quasi-Poisson regression model. To assess potential delayed and non-linear effects of air pollutants and Apparent Temperature (AT), a biometeorological index which represents human thermal comfort on IS, a lag non-linear model was fitted in a generalized additive model. The mortality rate followed a downward trend over the studied period, however admission rates progressively increased. Our results show that both increases and decreases in AT had a marked relationship with IS deaths, while hospital admissions were only associated with low AT. When analyzing the cumulative effects (for lag 0-14 days), with an AT of 1.7 °C (percentile 5%) a RR of 1.20 (95% CI, 1.05-1.37) for IS mortality and a RR of 1.09 (95% CI, 0.91-1.29) for morbidity is estimated. Concerning gender differences, men show higher risks of mortality in low temperatures and women in high temperatures. No significant relationship was found between air pollutant concentrations and IS morbi-mortality, but this result must be interpreted with caution, since there are strong spatial fluctuations of the former between nearby geographical areas that make it difficult to perform correlation analyses.

Air pollution and stroke. A new modifiable risk factor is in the air

Evidence from epidemiological studies has demonstrated that outdoor air pollution is now a well-known major problem of public health, mainly in low and middle income countries. Contrasting with myocardial infarction, there are few data on the association of air pollution and stroke.

METHODS

We propose a narrative literature review of the effects and the underlying biological mechanisms of short- and long-term exposure to air pollutants on stroke risk and mortality, using the following key-words: stroke, cerebrovascular events, ischemic and haemorrhage stroke, transient ischaemic attack, mortality, air pollution and air pollutants.

RESULTS

Twenty-one papers were selected. Air pollution, of which whose small particulate matter are the most toxic, contributes to about one-third of the global burden of stroke. We can identify vulnerable patients with classical neuro-vascular risk factors or a prior history of stroke or transient ischemic attack or persons living in low-income countries. Biological mechanisms of this new morbid association are discussed.

CONCLUSION

Air pollution should be recognized as a silent killer inducing stroke whose mortality rates remain elevated by its role as a new modifiable neurovascular risk factor, needing public health policies.

An Exposure Appraisal of Outdoor Air Pollution on the Respiratory Well-being of a Developing City Population

Zaria is the educational hub of northern Nigeria. It is a developing city with a pollution level high enough to be ranked amongst the World Health Organization’s (WHO) most polluted cities. The study appraised the influence of outdoor air pollution on the respiratory well-being of a population in a limited resource environment. With the approved ethics, the techniques utilized were: portable pollutant monitors, respiratory health records, WHO AirQ+ software, and the American Thoracic Society (ATS) questionnaire. They were utilized to acquire day-time weighted outdoor pollution levels, health respiratory cases, assumed baseline incidence (BI), and exposure respiratory symptoms among selected study participants respectively. The study revealed an average respiratory illness incidence rate of 607 per 100,000 cases. Findings showed that an average of 2648 cases could have been avoided if the theoretical WHO threshold limit for the particulate matter with diameter of <2.5/10 micron (PM_2.5/PM₁₀) were adhered to. Using the questionnaire survey, phlegm was identified as the predominant respiratory symptom. A regression analysis showed that the criteria pollutant PM_2.5, was the most predominant cause of respiratory symptoms among interviewed respondents. The study logistics revealed that outdoor pollution is significantly associated with respiratory well-being of the study population in Zaria, Nigeria.

Extended Risk Factors for Stroke Prevention

Stroke causes disability and high mortality, while it can be prevented by increasing public awareness of risk factors. The common known risk factors are hypertension, atrial fibrillation, heart failure, smoking, alcohol consumption, low physical activity, overweight and hypercholesterolemia. However, the deep understanding of risk factors is limited. Moreover, more risk factor emerges in recent years. To further increase the awareness of risk factors for stroke prevention, this review indicates the reasonable application of antihypertensive agents according to the age-dependent changes of hypertension, and some new risk factors including chronic kidney disease, obstructive sleep apnea, migraine with aura, working environment, genetic factors and air pollution. Therefore, internal risk factors (e.g. heredity, hypertension, hyperglycemia) and external risk factors (e.g. working environment, air pollution) are both important for stroke prevention. All of these are reviewed to provide more information for the pre-hospital prevention and management, and the future clinical studies.

Case-crossover analysis of short-term particulate matter exposures and stroke in the health professionals follow-up study

BACKGROUND

Stroke is a leading cause of morbidity and mortality in the United States. Associations between short-term exposures to particulate matter (PM) air pollution and stroke are inconsistent. Many prior studies have used administrative and hospitalization databases where misclassification of the type and timing of the stroke event may be problematic.

METHODS

In this case-crossover study, we used a nationwide kriging model to examine short-term ambient exposure to PM10 and PM2.5 and risk of ischemic and hemorrhagic stroke among men enrolled in the Health Professionals Follow-up Study. Conditional logistic regression models were used to obtain estimates of odds ratios (OR) and 95% confidence intervals (CI) associated with an interquartile range (IQR) increase in PM2.5 or PM10. Lag periods up to 3 days prior to the stroke event were considered in addition to a 4-day average. Stratified models were used to examine effect modification by patient characteristics.

RESULTS

Of the 727 strokes that occurred between 1999 and 2010, 539 were ischemic and 122 were hemorrhagic. We observed positive statistically significant associations between PM10 and ischemic stroke (ORlag0-3 = 1.26; 95% CI: 1.03-1.55 per IQR increase [14.46 μg/m3]), and associations were elevated for nonsmokers, aspirin nonusers, and those without a history of high cholesterol. However, we observed no evidence of a positive association between short-term exposure to PM and hemorrhagic stroke or between PM2.5 and ischemic stroke in this cohort.

CONCLUSIONS

Our study provides evidence that ambient PM10 may be associated with higher risk of ischemic stroke and highlights that ischemic and hemorrhagic strokes are heterogeneous outcomes that should be treated as such in analyses related to air pollution.

Urban air quality and associations with pediatric multiple sclerosis

Background

We previously identified air quality as a risk factor of interest for pediatric multiple sclerosis. The purpose of this study is to more closely examine the association between the six criteria air pollutants and pediatric MS as well as identify specific areas of toxic release using data from the Toxic Release Inventory.

Methods

Pediatric MS cases (N = 290) and healthy controls (N = 442) were included as part of an ongoing case-control study. We used the National Emissions Inventory system to estimate particulate exposure by county of residence for each participant. Proximity to Toxic Release Inventory (TRI) sites was also assessed using ArcGIS mapping tools. Risk-Screening Environmental Indicators (RSEI) classified counties at risk to exposure of environmental toxic releases.

Results

Fine particulate matter (PM _2.5), carbon monoxide (CO), sulfur dioxide (SO ₂), and lead air emissions were associated with increased odds for pediatric MS (P < 0.01) for those residing within 20 miles of an MS center. Most study participants (75%) resided within 5 miles of at least one TRI site; however, the mean total pounds of stack air releases was higher for sites near MS cases (81,000 tons) compared to those near healthy controls (35,000 tons, P = 0.002). Average RSEI scores did not differ significantly between cases and controls.

Conclusion

Out of several air pollutants examined, we show that fine particulate matter and three other criteria pollutants (SO ₂, CO, and lead) were statistically associated with higher odds for pediatric MS.

The Relationship Between Ambient Air Pollution and Acute Ischemic Stroke: A Time-Stratified Case-Crossover Study in a City-State With Seasonal Exposure to the Southeast Asian Haze Problem

STUDY OBJECTIVE

Studies are divided on the short-term association of air pollution with stroke. Singapore is exposed to seasonal transboundary haze. We aim to investigate the association between air pollution and stroke incidence in Singapore.

METHODS

We performed a time-stratified case-crossover analysis on all ischemic stroke cases reported to the Singapore Stroke Registry from 2010 to 2015. Exposure on days was compared with control days on which exposure did not occur. Control days were chosen on the same day of the week earlier and later in the same month in the same year. We fitted a conditional Poisson regression model to daily stroke incidence that included Pollutant Standards Index and environmental confounders. The index was categorized according to established classification (0 to 50=good, 51 to 100=moderate, and ≥101=unhealthy). We assessed the relationship between stroke incidence and Pollutant Standards Index in the entire cohort and in predetermined subgroups of individual-level characteristics.

RESULTS

There were 29,384 ischemic stroke cases. Moderate and unhealthy Pollutant Standards Index levels showed association with stroke occurrence, with incidence risk ratio 1.10 (95% confidence interval 1.06 to 1.13) and 1.14 (95% confidence interval 1.03 to 1.25), respectively. Subgroup analyses showed generally significant association, except in Indians and nonhypertensive patients. The association was significant in subgroups aged 65 years or older, women, Chinese, nonsmokers and those with history of diabetes, hypertension, and hyperlipidemia. Stratified by age and smoking, the risk diminished in smokers of all ages. Risk remained elevated for 5 days after exposure.

CONCLUSION

We found a short-term elevated risk of ischemic stroke after exposure to air pollution. These findings have public health implications for stroke prevention and emergency health services delivery.

A review of epidemiological research on stroke and dementia and exposure to air pollution

Background

Outdoor air pollution is now a well-known risk factor for morbidity and mortality, and is increasingly being identified as a major risk factor for stroke.

Methods

A narrative literature review of the effects of short and long-term exposure to air pollution on stroke and dementia risk and cognitive functioning.

Results

Ten papers on stroke and 17 on dementia were selected. Air pollution, and in particular small particulate matter, contributes to about one-third of the global stroke burden and about one-fifth of the global burden of dementia. It particularly affects vulnerable patients with other vascular risk factors or a prior history of stroke in low- and medium-income countries. New pathophysiological mechanisms of the cause-effect associations are suggested.

Conclusion

Air pollution should be considered as a new modifiable cerebrovascular and neurodegenerative risk factor. This massive worldwide public health problem requires environmental health policies able to reduce air pollution and thus the stroke and dementia burden.

Short-term exposure to traffic-related air pollution and ischemic stroke onset in Barcelona, Spain

OBJECTIVE

To assess the relationship between short-term exposure to outdoor ambient air pollutants (fine particulate matter [PM_2.5] and black carbon [BC]), ischemic stroke (IS) and its different subtypes, and the potential modifying effect of neighborhood greenspace and noise.

METHODS

This time-stratified case-crossover study was based on IS and transient ischemic attacks (TIA) recorded in a hospital-based prospective stroke register (BASICMAR 2005-2014) in Barcelona (Catalonia, Spain). Daily and hourly pollutant concentrations and meteorological data were obtained from monitoring stations in the city. Time-lags (from previous 72h to acute stroke onset) were analyzed. Greenness and noise were determined from the Normalized Difference Vegetation Index (NDVI) and daily average noise level at the street nearest to residential address, respectively.

RESULTS

The 2742 cases with known onset date and time, living in the study area, were analyzed. After adjusting for temperature, no statistically significant association between pollutants exposure and overall stroke risk was found. In subtype analysis, an association was detected between BC exposure at 24-47h (odds ratio, 1.251; 95% confidence interval [CI], 1.001-1.552; P = 0.042) and 48-72h (1.211; 95% CI, 0.988-1.484; P = 0.065) time-lag prior to stroke onset and large-artery atherosclerosis subtype. No clear modifying effect of greenness or noise was observed.

CONCLUSIONS

Overall, no association was found between PM_2.5 and BC exposure and acute IS risk. By stroke subtype, large-artery atherosclerotic stroke could be triggered by daily increases in BC, a diesel fuel-related pollutant in the study area.

Examining the contributions of environmental quality to pediatric multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a presumed autoimmune disease caused by genetic and environmental factors. It is hypothesized that environmental exposures (such as air and water quality) trigger the innate immune response thereby activating a pro-inflammatory cascade.

OBJECTIVE

To examine potential environmental factors in pediatric MS using geographic information systems (GIS).

METHODS

Pediatric MS cases and healthy controls were identified as part of an ongoing multicenter case-control study. Subjects' geographic locations were mapped by county centroid to compare to an Environmental Quality Index (EQI). The EQI examines 5 individual environmental components (air, land, water, social, built factors). A composite EQI score and individual scores were compared between cases and controls, stratified by median proximity to enrollment centers (residence <20 or ≥20 miles from the recruiting center), using logistic regression.

RESULTS

Of the 287 MS cases and 445 controls, 46% and 49% respectively live in areas where the total EQI is the highest (worst environmental quality). Total EQI was not significantly associated with the odds for MS (p = 0.90 < 20 miles from center; p = 0.43 ≥ 20 miles); however, worsening air quality significantly impacted the odds for MS in those living near a referral center (OR = 2.83; 95%CI 1.5, 5.4) and those who reside ≥ 20 miles from a referral center (OR = 1.61; 95%CI 1.2, 2.3).

CONCLUSION

Among environmental factors, air quality may contribute to the odds of developing MS in a pediatric population. Future studies will examine specific air constituents and other location-based air exposures and explore potential mechanisms for immune activation by these exposures.

Associations between exhaust and non-exhaust particulate matter and stroke incidence by stroke subtype in South London

BACKGROUND

Airborne particulate matter (PM) consists of particles from diverse sources, including vehicle exhausts. Associations between short-term PM changes and stroke incidence have been shown. Cumulative exposures over several months, or years, are less well studied; few studies examined ischaemic subtypes or PM source.

AIMS

This study combines a high resolution urban air quality model with a population-based stroke register to explore associations between long-term exposure to PM and stroke incidence.

METHOD

Data from the South London Stroke Register from 2005-2012 were included. Poisson regression explored association between stroke incidence and long-term (averaged across the study period) exposure to PM2.5(PM<2.5μm diameter) and PM10(PM<10μm), nitric oxide, nitrogen dioxide, nitrogen oxides and ozone, at the output area level (average population=309). Estimates were standardised for age and sex and adjusted for socio-economic deprivation. Models were stratified for ischaemic and haemorrhagic strokes and further broken down by Oxford Community Stroke Project classification and Trial of ORG 10172 in Acute Stroke Treatment (TOAST) classification.

RESULTS

1800 strokes were recorded (incidence=42.6/100,000 person-years). No associations were observed between PM and overall ischaemic or haemorrhagic incidence. For an interquartile range increase in PM2.5, there was a 23% increase in incidence (Incidence rate ratio=1.23 (95%CI: 1.03-1.44)) of total anterior circulation infarcts (TACI) and 20% increase for PM2.5 from exhausts (1.20(1.01-1.41)). There were similar associations with PM10, overall (1.21(1.01-1.44)) and from exhausts (1.20(1.01-1.41)). TACI incidence was not associated with non-exhaust sources. There were no associations with other stroke subtypes or pollutants.

CONCLUSION

Outdoor air pollution, particularly that arising from vehicle exhausts, may increase risk of TACI but not other stroke subtypes.