A number of factors have been associated with the onset of myocardial infarction, including physical exertion, drug abuse, heavy meals, stress, or increases in air pollution. Which of these triggers is the most important or relevant has not previously been investigated either at the population or the individual level.

Nawrot and colleagues reviewed 36 epidemiological studies and ranked triggers from the highest to the lowest odds ratio (OR) for myocardial infarction (see table).  When both the OR and the prevalences of exposure were taken into account, the highest population attributable fraction (PAF) was estimated for traffic exposure (7.4%), followed by physical exertion (6.2%), alcohol (5.0%), coffee (5.0%), a change in air quality (4.8%), negative emotions (3.9%), anger (3.1%), heavy metal (2.7%), positive emotions (2.4%), sexual activity (2.2%), cocaine use (0.9%), marijuana smoking (0.8%), and respiratory infections (0.6%).

Conclusions:

When the magnitude of the risk and the prevalence in the population are considered together, air pollution appears to be one of the most important triggers of myocardial infarction, and is of a similar magnitude to other well accepted triggers such as alcohol, coffee, and physical exertion.

• Nawrot TS, Perez L, Kunzli N, et al.  Public health importance of triggers of myocardial infarction: a comparative risk assessment.  Lancet 2011; 377: 732-740.