A Case-Crossover Analysis of Out-of-Hospital Cardiac Arrest and Air Pollution Katherine B. Ensor, Loren H. Raun,and David Persse
Circulation.2013;127:1192-1199, published online before print February 13 2013, doi:10.1161/CIRCULATIONAHA.113.000027
Abstract
Background—Evidence of an association between the exposure to air pollution and overall cardiovascular morbidity and mortality is increasingly found in the literature. However, results from studies of the association between acute air pollution exposure and risk of out-of-hospital cardiac arrest (OHCA) are inconsistent for fine particulate matter, and, although pathophysiological evidence indicates a plausible link between OHCA and ozone, none has been reported. Approximately 300 000 persons in the United States experience an OHCA each year, of which >90% die. Understanding the association provides important information to protect public health. Methods and Results—The association between OHCA and air pollution concentrations hours and days before onset was assessed by using a time-stratified case-crossover design using 11 677 emergency medical service–logged OHCA events between 2004 and 2011 in Houston, Texas. Air pollution concentrations were obtained from an extensive area monitor network. An average increase of 6 µg/m3 in fine particulate matter 2 days before onset was associated with an increased risk of OHCA (1.046; 95% confidence interval, 1.012–1.082). A 20-ppb ozone increase for the 8-hour average daily maximum was associated with an increased risk of OHCA on the day of the event (1.039; 95% confidence interval, 1.005–1.073). Each 20-ppb increase in ozone in the previous 1 to 3 hours was associated with an increased risk of OHCA (1.044; 95% confidence interval, 1.004–1.085). Relative risk estimates were higher for men, blacks, or those aged >65 years. Conclusions—The findings confirm the link between OHCA and fine particulate matter and introduce evidence of a similar link with ozone.
Where do the authors work, and what are their areas of expertise? Note any other publications by the authors with relevance to the 6Cities project.
Katherine B. Ensor is a Professor of Statistics at Rice University. She has an interest in environmental statistics, and has done projects involving modeling groundwater contamination and predicting ozone levels.
Loren H. Raun is a Faculty Fellow in Statistics at Rice University. She has many research papers dealing with air & water pollution and environmental health affects. One paper that looks especially promising is:
Raun Loren H, Kathy Ensor, David Persse "Reducing exposure to air pollution triggered asthma attacks using community level strategies: A case crossover analysis." Environmental Health (February 2014) Submitted
David Persse is the Medical Director for Emergency Medical Services for the city of Houston, and is the Public Health Authority for the Department of Health & Human Services for the City of Houston.
What are the main findings or arguments presented in the article or report?
An increase in the daily average of particulate matter was associated with increased cardiac arrest risks for 2 days.An increase in hourly average of ozone was associated with increased cardiac arrest risk for 2 hours (association of increased cardiac arrest risk for the day of increased ozone).
Describe at least three ways that the argument is supported.
They looked at the levels of ozone and particulate matter on a daily and hourly scale, and compared that with the data from emergency medical services. They found correlations with 95% confidence, and their statistical methods are detailed in the report.
What three (or more) quotes capture the message of the article or report?
"We find consistent evidence of an association between OHCAand exposure to ozone in Houston, Texas at short time scalesup to 3 hours in duration and also at the daily level on the dayof the event. For exposure to PM 2.5, an association is found for2 days before the event."
"In an effort to better understand the association of airpollution and OHCA, we used an extensive air-monitoringnetwork and a large emergency medical service (EMS) calldatabase spanning 8 years."
"...We bring the mostcomprehensive data set to date to this literature, in terms ofduration of the study, number of pollution monitors included,and the number of OHCA events studied. The implicationsof this work are improved health policy and action with theobjective of reducing the number of annual OHCA currentlyat ≈ 300,000 in the nation and 1460 in Houston."
What were the methods, tools and/or data used to produce the claims or arguments made in the article or report?
They used databases from the Emergency Medical Services to compare the cardiac arrest incidents with air pollution data provided by the city of Houston.
They used a "case-crossover" design to statistically analyze these databases, with exploratory sensitivity analysis and a single lag model. They also used time-stratified sampling procedures to limit bias.
How (if at all) are health disparities or other equity issues addressed in the article or report?
They stratifies the analysis by age, sex, and race.
"Analysis of stratification of the cases by the demographic characteristics of the data (age, sex, and race) found thatthe risk from exposure to ozone or PM2.5 is highest for men (1.051; 95% CI, 1.006–1.097), those of black ethnicity (1.053; 95% CI, 1.003–1.105), and >65 years of age (1.049; 95% CI, 1.000–1.100)"
Where has this article or report been referenced or discussed? (In some journals, you can see this in a sidebar.)
This article has been cited by similar studies, including studies on the affects of air pollution on incidences of cardiac arrest in Perth and Stockholm. This means that the study and the statistical methods discussed are helpful for other cities around the world. This paper is also referenced in a study of air pollution and its affects on labor and delivery, a very important aspect of public health that could be negatively affected.
Can you learn anything from the article or report’s bibliography that tells us something about how the article or report was produced?
The report was funded by the city of Houston. The report is special because it uses a larger amount of data than any similar studies, in part due to this cooperation with the city.
What three points, details or references from the text did you follow up on to advance your understanding of how air pollution science has been produced and used in governance and education in different settings?
It was quite surprising to me how complex the statistical models are
LINK TO ARTICLE
A Case-Crossover Analysis of Out-of-Hospital Cardiac Arrest and Air Pollution
Katherine B. Ensor, Loren H. Raun,and David Persse
Circulation. 2013;127:1192-1199, published online before print February 13 2013, doi:10.1161/CIRCULATIONAHA.113.000027
Abstract
Background—Evidence of an association between the exposure to air pollution and overall cardiovascular morbidity and mortality is increasingly found in the literature. However, results from studies of the association between acute air pollution exposure and risk of out-of-hospital cardiac arrest (OHCA) are inconsistent for fine particulate matter, and, although pathophysiological evidence indicates a plausible link between OHCA and ozone, none has been reported. Approximately 300 000 persons in the United States experience an OHCA each year, of which >90% die. Understanding the association provides important information to protect public health.Methods and Results—The association between OHCA and air pollution concentrations hours and days before onset was assessed by using a time-stratified case-crossover design using 11 677 emergency medical service–logged OHCA events between 2004 and 2011 in Houston, Texas. Air pollution concentrations were obtained from an extensive area monitor network. An average increase of 6 µg/m3 in fine particulate matter 2 days before onset was associated with an increased risk of OHCA (1.046; 95% confidence interval, 1.012–1.082). A 20-ppb ozone increase for the 8-hour average daily maximum was associated with an increased risk of OHCA on the day of the event (1.039; 95% confidence interval, 1.005–1.073). Each 20-ppb increase in ozone in the previous 1 to 3 hours was associated with an increased risk of OHCA (1.044; 95% confidence interval, 1.004–1.085). Relative risk estimates were higher for men, blacks, or those aged >65 years.
Conclusions—The findings confirm the link between OHCA and fine particulate matter and introduce evidence of a similar link with ozone.
Katherine B. Ensor is a Professor of Statistics at Rice University. She has an interest in environmental statistics, and has done projects involving modeling groundwater contamination and predicting ozone levels.
Loren H. Raun is a Faculty Fellow in Statistics at Rice University. She has many research papers dealing with air & water pollution and environmental health affects. One paper that looks especially promising is:
Raun Loren H, Kathy Ensor, David Persse "Reducing exposure to air pollution triggered asthma attacks using community level strategies: A case crossover analysis." Environmental Health (February 2014) Submitted
David Persse is the Medical Director for Emergency Medical Services for the city of Houston, and is the Public Health Authority for the Department of Health & Human Services for the City of Houston.
An increase in the daily average of particulate matter was associated with increased cardiac arrest risks for 2 days.An increase in hourly average of ozone was associated with increased cardiac arrest risk for 2 hours (association of increased cardiac arrest risk for the day of increased ozone).
They looked at the levels of ozone and particulate matter on a daily and hourly scale, and compared that with the data from emergency medical services. They found correlations with 95% confidence, and their statistical methods are detailed in the report.
This article has been cited by similar studies, including studies on the affects of air pollution on incidences of cardiac arrest in Perth and Stockholm. This means that the study and the statistical methods discussed are helpful for other cities around the world. This paper is also referenced in a study of air pollution and its affects on labor and delivery, a very important aspect of public health that could be negatively affected.
- Can you learn anything from the article or report’s bibliography that tells us something about how the article or report was produced?
The report was funded by the city of Houston. The report is special because it uses a larger amount of data than any similar studies, in part due to this cooperation with the city.