Atrial fibrillation and risk of myocardial infarction by sex and time since diagnosis. The Tromsø Study 1994–2021

The relationship between atrial fibrillation (AF) and myocardial infarction (MI) remain unclear. We aimed to examine the sex-specific risk of MI, ST-segment elevation MI (STEMI) and non-ST-segment elevation MI (NSTEMI) in participants with AF, overall and by time since AF diagnosis.

We followed 25 132 participants (53% women) from the Tromsø Study (1994–95) without AF and MI at baseline through 2021. Cox proportional- and Fine-Gray sub-distribution-hazard regression assessed AF as a risk factor for MI, STEMI and NSTEMI overall and by time since AF diagnosis (0 to <0.5, 0.5 to <1, 1 to <5, 5 to <10 and ≥10 years). During follow-up, 115 women and 124 men experienced incident AF and subsequent MI. AF was associated with increased hazard of MI in women (sub-distribution hazard ratio [sHR] 1.39, 95% confidence interval [CI] 1.12–1.72), but not in men. In women, the hazard of MI increased 1–10 + years since AF, peaking at ≥10 years (sHR 1.75, 95% CI 1.07–2.84). In men, hazard was increased within the first six months (sHR 2.27, 95% CI 1.45–3.54) but not thereafter. STEMI hazard was increased only in men within six months. NSTEMI hazard was elevated in women 1–10 + years since AF and in men within the first year.

AF is a risk factor for MI in both sexes, but risk patterns differ. Women are at increased hazard of NSTEMI 1–10 + years since AF, while men are at increased hazard of STEMI within six months and NSTEMI within the first year.