Early detection of atrial fibrillation (AF) is essential for preventing ischemic stroke and other cardiovascular complications. However, the incidence and prognosis of AF in the general middle-aged population remain unclear. In Japan, annual health screenings for employees include mandatory ECGs, offering a unique opportunity to fill this evidence gap. This retrospective cohort study aimed to evaluate the incidence and subsequent cardiovascular outcomes of screening-detected AF in the general working population in Japan, using the Japan Health Insurance Association database, which covers one-quarter of the working-age population of that country. From individuals 35 to 59 years of age who underwent annual health screenings between April 2015 and March 2020, excluding those with a history of cardiovascular disease, those with initial AF detection upon screening ECGs were identified. The primary outcome was hospitalization for ischemic stroke. The secondary outcomes were all-cause death and hospitalization for heart failure. The association between screening-detected AF and outcomes was evaluated using adjusted subdistribution hazard models compared with matched controls.

Findings: Among 9.5 million individuals included in our study, 11,790 initial AF cases  were detected. Individuals with AF were older and more likely to be male compared with non-AF cases (91.6% versus 63.6%, respectively). Among these individuals with screening-detected AF, the 3-year incidences of ischemic stroke, all-cause death, and heart failure were 1.83% , 0.78%, and 3.87%, respectively. Compared with age- and sex-matched controls, individuals with AF had a higher risk of incident ischemic stroke, all-cause death, and heart failure.

These findings highlight the association of screening-detected AF with stroke and heart failure, warranting further study into AF as an early sign of heart failure and optimal cardiovascular risk reduction strategies after AF detection in the general middle-aged population.