Triggering of myocardial infarction by heat exposure is modified by medication intake.

Acute myocardial infarction (MI) can be triggered by heat exposure, but it remains unknown whether patients taking certain cardiovascular medications have elevated vulnerability. Based on a validated and complete registration of all 2,494 MI cases in Augsburg, Germany, during warm seasons (May to September) from 2001 to 2014, here we show that heat-related non-fatal MI risk was elevated among users of anti-platelet medication and beta-receptor blockers, respectively, but not among non-users, with significant differences between users and non-users. We also found that these effect modifications were stronger among younger patients (25-59 years), who had a lower prevalence of pre-existing coronary heart disease (CHD, a potential confounder by indication), than among older patients (60-74 years), who had a higher prevalence of pre-existing CHD. Users of these medications may be more vulnerable than non-users to non-fatal MI risk due to heat exposure. Further research is needed to disentangle effect modification by medication use from effect modification by pre-existing CHD.