Introduction:
Air pollution is associated with greater cardiovascular event risk, but which types of events and the specific at-risk individuals remain unknown.
Hypothesis:
Short-term exposure to fine particulate matter (PM
2.5
) is associated with greater risk of acute coronary syndromes (ACS), including ST elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), and unstable angina (USA).
Methods:
ACS events treated at Intermountain Healthcare hospitals in Utah’s urban Wasatch Front region between September 10, 1993 and May 15, 2014 were included if the patient resided in that area (N=16,314). A time-stratified case-crossover design was performed matching the PM
2.5
exposure at the time of event with periods when the event did not occur (referent), for STEMI, NSTEMI, and USA. Patients served as their own controls. Odds ratios (OR) were determined for exposure threshold versus linear, non-threshold models.
Results:
In STEMI, NSTEMI, and USA patients, age averaged 62, 64, and 63 years; males constituted 73%, 66%, and 68%; current or past smoking was prevalent in 33%, 25%, and 26%; and significant coronary artery disease (CAD) (defined as ≥1 coronary with ≥70% stenosis) was found among 95%, 75%, and 74%, respectively. Short-term PM
2.5
exposure was associated with ACS events (Table).
Conclusions:
Short-term exposure of PM
2.5
was strongly associated with greater risk of STEMI, especially in patients with angiographic CAD. No association with NSTEMI was found, and only a weak effect for USA. This study supports a PM
2.5
exposure threshold of 25 μg/m
3
, below which little exposure effect is seen, while the effect is linear above that level.
Short-term air pollution concentration variations and ST-elevation myocardial infarction: A case-crossover study from the SCALIM registry