Mendelian randomization analysis of genetic data from FinnGen and UK Biobank reveals that obstructive sleep apnea causally increases myocardial infarction risk by 0.24% per log-unit increase in OSA liability. Body mass index emerges as the primary mediator, explaining 36% of this association, while atrial fibrillation represents an independent pathway linking sleep disorders to heart attacks. This genetic approach provides compelling evidence for causality beyond observational associations that could be confounded by shared lifestyle factors. The findings illuminate why sleep apnea patients face elevated cardiovascular mortality—not merely through blood pressure elevation as traditionally assumed, but via obesity-driven metabolic disruption and cardiac rhythm disturbances. For the estimated 936 million adults worldwide with OSA, this research underscores the cardiovascular urgency of addressing sleep-disordered breathing. However, the modest effect size suggests other factors significantly influence heart attack risk. Since this preprint awaits peer review, the precise mediation percentages and statistical significance may be refined. The work represents solid confirmatory evidence using robust genetic methods, strengthening the scientific foundation for treating OSA as cardiovascular disease prevention.