Atrial fibrillation (AF) is a common cardiac arrhythmia that is associated with an increased risk of major adverse cardiovascular events (MACE). The main goal was to analyze the links and associations between AF and MACE. A multicenter, observational, retrospective, community-based study of a cohort (n = 40,297) of the general population aged 65-95 years between 1 January 2015 and 31 December 2021 without a previous diagnosis of AF or MACE in the Primary Care setting. 2574 people (6.39%) developed a first AF event, resulting in an overall incidence of 8.9/1000 people-years [CI95% 8.6-9.2]. The incidence of MACE among those with AF was 75.1/1000 people-years [CI95% 70.8-79.5], whereas among those without AF, it was 20.6/1000 people-years [CI 95% 20.2-21.1], resulting in a rate ratio of 3.65 [CI 95% 3.43-3.88, p < 0.001]. Besides, the incidence of HF with AF was 40.1 people-years [CI 95% 37.1-43.2], while in the group without AF, it was 8.3 people-years [CI 95% 7.9-8.6, p < 0.001], with a rate ratio of 4.85 [CI 95% 4.45-55.3, p < 0.001]. Before an AF diagnosis, there is already a higher risk of chronic kidney disease, ischemic cardiopathy, and peripheral artery disease. A higher risk of poor nutritional status was detected among those with MACE (49.7% vs. 26.6%, p < 0.001). AF diagnosis increases the incidence of heart failure fourfold. Additional information is required to establish the connection between AF, major adverse cardiovascular events, and nutritional status.