Air Pollution and Subtypes, Severity and Vulnerability to Ischemic Stroke—A Population Based Case-Crossover Study

Background: Air quality is an important determinant of cardiovascular health such as ischemic heart disease and acute ischemic stroke (AIS) with substantial mortality and morbidity reported across the globe. However, associations between air quality and AIS in the current literature remain inconsistent, with few studies undertaken in cosmopolitan cities located in the tropics. Objectives: We evaluated the associations between individual ambient air pollutants and AIS. Methods: We performed a nationwide, population-based, time-stratified case-crossover analysis on all AIS cases reported to the Singapore Stroke Registry from 2009 to 2018. We estimated the incidence rate ratio (IRR) of AIS across different concentrations of each pollutant by quartiles (referencing the 25th percentile), in single-pollutant conditional Poisson models adjusted for time-varying meteorological effects. We stratified our analysis by predetermined subgroups deemed at higher risk. Results: A total of 51,675 episodes of AIS were included. Ozone (O3) (IRR4th quartile: 1.05, 95% confidence interval (CI): 1.01–1.08) and carbon monoxide (CO) (IRR2nd quartile: 1.05, 95% CI: 1.02–1.08, IRR3rd quartile: 1.07, 95% CI: 1.04–1.10, IRR4th quartile: 1.07, 95% CI: 1.04–1.11) were positively associated with AIS incidence. The increased incidence of AIS due to O3 and CO persisted for 5 days after exposure. Those under 65 years of age were more likely to experience AIS when exposed to CO. Individuals with atrial fibrillation (AF) were more susceptible to exposure from O3, CO, and PM10. Current/ex-smokers were more vulnerable to the effect of O3. Conclusion: Air pollution increases the incidence of AIS, especially in those with AF and in those who are current or ex-smokers.

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P2782Specific air pollution indicators are related to recurrence of ischemic stroke-a nationwide cohort study with surveillance system by time-stratified case-crossover study design

European Heart Journal ◽

10.1093/eurheartj/ehz748.1098 ◽

2019 ◽

Vol 40 (Supplement_1) ◽

Author(s):

A H Li ◽

C L Chan ◽

C Y Wu

Keyword(s):

Air Pollution ◽

Cohort Study ◽

Heart Disease ◽

Ischemic Stroke ◽

Crossover Study ◽

Study Design ◽

Individual Characteristics ◽

Research Database ◽

Pollution Indicators ◽

Case Crossover

Abstract Background and objective Ischemic stroke (IS) is the 2nd killer in Taiwan. There was no studies of air pollution indicators (API's) in nationwide database, on their relationship to IS recurrence. We aimed to analyze the IS incidences, its recurrence risk related to API's. Methods We used LHID 2005 (Longitudinal Health Insurance Database 2005) from National Health Institute Research Database (NHIRD), i.e. the entire original claim data of randomly sampled 1,000,000 beneficiaries in 2005. The national API surveillance database (PM2.5, PM10, CO, SO2, NO,NO2, NOx, O3) was incorporated with it. The IS incidences was computed by obtaining 1st admission for IS (ICD9–433, 434, 435), and the recurrence was on second IS within 30 days of 1st one. To minimize the confounding effect of comorbidities, we used a time-stratified case-crossover study design, proposed by Maclure (1991), for transient effects on acute events' risk; it is characterized by that each subject serves as his or her own control according to fixed individual characteristics, such as age, gender, lifestyle, socio-economic status, genetics and physiological status, etc. The API exposure was analyzed on the re-admission date (lag0), and 1 to 6 day before re-admission (lag1, lag2 ... lag6 etc.). Results The IS recurrence-readmission is strongly associated with SO2 peak level 5 days before (lag5 – 95% CI: 1.011–1.023, p=0.004) for patients above 20. Significant association of IS recurrence with PM2.5, SO2 O3, SO2 is noted in different patient groups. Table 1. Basic demographics of ischemic stroke in Taiwan (2005–2013) Ischemic stroke N % Age, mean ± SD 68.94±12.8 Male 11832 58% Other forms of chronic ischemic heart disease (ICD9–414) 1496 7% Diabetes mellitus (ICD9–250) 6679 32% Essential hypertension (ICD9–401) 9038 44% Disorders of lipoid metabolism (ICD9–272) 4142 20% Heart failure (ICD9–428) 670 3% Hypertensive heart disease (ICD9–402) 2333 11% Figure 1. Hazard Ratio of specific API's in IS (only shown with statistical significance): those left to line 1.0 with protective effect and vice versa (20–45, 46–64 and 65 above representative meaning for age range). Conclusion Specific API's are strongly associated with IS recurrence. We need a prospective cohort study designed on this topic.

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