Question: I heard that men between 18-35 have a higher rate of heart complications, true or false. If true, why?

Answer: I’m going to narrow your question a bit to focus on one heart complication– myocarditis– which is associated with COVID, both infection and vaccination.  Myocarditis, or inflammation of the heart muscle, is a rare complication usually caused by a viral infection (e.g. not just COVID, but other viral infections too).  It is most frequently diagnosed in young adults and is more common in men than women.  When it comes to COVID vaccination, myocarditis has been found to be a rare, usually mild side effect of COVID mRNA vaccinations.  To put “rare risk” in perspective, one recent study out of Israel published in the New England Journal of Medicine found “a rate of approximately 1 per 26,000 males and 1 per 218,000 females after the second vaccine dose, with the highest risk again among young male recipients.”  Meanwhile, SARS-CoV-2 is associated with much higher risk of myocarditis; another recent study published in NEJM found the relative risk of COVID-assicated myocarditis to be much higher than the risk in the general population and much higher than the risk associated with mRNA vaccination “(risk ratio, 18.28; 95% CI, 3.95 to 25.12; risk difference, 11.0 events per 100,000 persons; 95% CI, 5.6 to 15.8) and of additional serious adverse events, including pericarditis, arrhythmia, deep-vein thrombosis, pulmonary embolism, myocardial infarction, intracranial hemorrhage, and thrombocytopenia.”  Scientists still aren’t sure why myocarditis incidence is more frequent among young men.  One hypothesis is that sex hormones, including testosterone, differentially impact the immune system’s reaction to infection.  In summation, yes, young men experience higher rates of myocarditis; we aren’t sure why, but it may be due to the interplay of sex hormones and the immune system.