Immediate risk of myocardial infarction following physical exertion, tea, and coffee: A case-crossover study in Thailand

Background Physical exertion and caffeine consumption are associated with acute myocardial infarction (MI). However, physical exertion and caffeine consumption have not been examined as immediate triggers of MI in low and middle-income countries. Objective Using a self-matched case-crossover design, we examined the acute risk of MI in the hour following episodes of physical exertion, caffeinated coffee, and tea consumption among MI survivors in Thailand. Methods A total of 506 Thai participants (women = 191, men = 315) were interviewed between 2014 and 2017 after sustaining an acute MI. We compared each subject’s exposure to physical exertion and consumption of caffeine- containing beverages in the hour preceding the onset of MI with the subject’s expected usual frequency in the prior year to calculate relative risks (RRs) and 95% confidence intervals (95%CIs). Results Of the 506 participants, 47 (9.3%) engaged in moderate or heavy physical exertion, 6 (1.2%) consumed tea, and 21 (4.2%) consumed coffee within the hour before MI. The relative risk of MI after moderate or heavy physical exertion was 3.0 (95% CI 2.2–4.2) compared to periods of no exertion, with a higher risk among more sedentary participants compared to active participants. Compared to times with no caffeinated beverage consumption, there was a higher risk of MI in the hour following consumption of caffeinated tea (RR = 3.7; 95% CI: 1.5–9.3) and coffee (RR = 2.3; 95%CI: 1.4–3.6). Conclusion Physical exertion, coffee and tea consumption were associated with a higher risk of MI in the subsequent hour compared to times when the participants were sedentary or did not consume caffeinated beverages. Our study identifies high-risk populations for targeted screening and intervention to prevent acute MI.