This report contains two studies, by Drs. Annette Peters and Douglas Dockery, a Commentary for each study, and an Integrative Discussion of both studies.
Part I. Air Pollution, Personal Activities, and Onset of Myocardial Infarction in as Case-Crossover Study Annette Peters, Stephanie von Klot, Margit Heier, Ines Trentinaglia, Josef Cyrys, Allmut Hörmann, Michael Hauptmann, H Erich Wichmann, and Hannelore Löwel.
Dr. Peters and her colleagues evaluated the association between nonfatal myocardial infarction (MI) and exposure to particulate matter just prior to the event. She asked 691 patients in hospitals in Augsburg, Germany who survived an MI to provide hourly details about their activities 4 days before MI onset. The investigators used a case-crossover analysis to determine whether exposure to pollutants was associated with onset of MI. They measured levels of ultrafine particles, PM2.5 and PM10 in ambient air in the city of Augsburg. They also obtained information about weather conditions and levels of gaseous pollutants (NO2, CO, SO2, and ozone). For potential risk factors that would be not affected by MI onset, the investigators compared the results from unidirectional analyses with those from bidirectional analyses, in which control periods were selected both before and after the outcome of interest.
Part II. Association of Air Pollution with Confirmed Arrhythmias Recorded by Implanted Defibrillators Douglas Dockery, Heike Luttmann-Gibson, David Q Rich, Mark S Link, Joel D Schwartz, DIane R Gold, Petros Koutrakis, Richard L Verrier, and Murray A Mittleman.
Dr. Dockery and colleagues assessed the correlation between short-term increases in ambient concentrations of particulate matter and the risk of possibly life-threatening arrhythmias in patients with implanted cardioverter defibrillators (ICDs). An ICD is programmed to respond when the heart rate exceeds a preset number of beats per minute; it records and stores the heartbeat pattern during an arrhythmic episode and (if necessary) delivers an electrical stimulus to return the heart rate to a normal rhythm. The investigators studied 195 patients from Boston, MA who had either single or dual-chamber ICD's and used logistic regression models to determine whether exposure to pollutants (PM2.5, ultrafine particles, black carbon, sulfate, NO2, CO, SO2, and ozone) was associated with arrhythmias. In addition, they evaluated patients' clinical information in some analyses to determine whether specific characteristics (e.g., diagnosis at ICD implantation, medication use, occurrence of multiple arrhythmias) would modify a pollutant's effects.