Background: Left atrial dimension (LAD) and other parameters of echocardiography have been reported to be associated with the risk of atrial fibrillation (AF). However, few studies have investigated the associations between echocardiographic parameters and the risk of AF in the Asian general population, which has a low AF incidence.

Methods: A prospective cohort study was performed in 1,424 individuals in the Suita study with echocardiographic parameters, including LAD, and no history of AF. After echocardiography, the participants were followed using 12-lead electrocardiography and questionnaires to detect AF incidence. The multivariable-adjusted hazard ratios (HRs) of echocardiographic parameters for AF incidence were estimated after adjustment for the risk factors of the AF risk score.

Results: During the median 6.0 years of follow-up, 31 AF cases occurred. The multivariable-adjusted HR of a 1-mm increase in LAD for AF was 1.18 (95% confidence interval [CI], 1.08–1.28). The multivariable-adjusted HR for AF of a 1-standard-deviation increase in LAD was higher than that of left ventricular internal dimensions in diastole, left ventricular mass, ejection fraction, and percent fractional shortening, and it was the only significant factor. In 667 participants with both LAD and LA volume (LAV) measurements, LAD and LAV were independently associated with the risk of AF incidence.

Conclusions: LAD on echocardiography was an independent risk factor of incident AF in the Japanese population. LAD might be useful for identifying individuals with a high risk of AF in health check-ups of the general population.