IMPORTANCE: Improving health status, including symptoms and quality of life, is a key goal in the management of atrial fibrillation (AF). However, whether improvements in patient-reported health status are associated with subsequent clinical outcomes remains unclear. OBJECTIVE: To evaluate the association between changes in health status and long-term adverse clinical outcomes in patients with AF. DESIGN, SETTING, AND PARTICIPANTS: This cohort study used data from a prospective multicenter registry in Japan that enrolled patients aged 22 to 94 years with newly diagnosed AF or who were newly referred for AF management between September 20, 2012, and May 22, 2018. The registry collected follow-up data for up to 5 years. Eligible patients completed the Atrial Fibrillation Effect on Quality of Life patient-reported outcome measure (PROM) questionnaire at both baseline and 1-year follow-up. Clinical outcomes were assessed for 4 years following the 1-year AF PROM assessment. Data were analyzed between February 7 and July 14, 2025. EXPOSURE: One-year change in the AF PROM overall summary score. MAIN OUTCOMES AND MEASURES: The primary outcome was a composite of all-cause death, heart failure hospitalization, and stroke or transient ischemic attack over 4 years. Multivariable hierarchical regression models adjusted for baseline score, clinical factors, and comorbidities were used to evaluate associations between 1-year change in AF PROM overall summary score and outcomes. RESULTS: Among 2744 patients (mean [SD] age, 67.8 [11.1] years; 1868 male [68.1%]; 1357 [49.6%] with paroxysmal AF), 1408 (51.3%) had improved health status (overall summary score increase of ≥5 points), 833 (30.4%) had stable health status, and 503 (18.3%) had worsened health status (overall summary score decrease of ≥5 points). During a mean (SD) follow-up of 3.1 (1.4) years after the 1-year assessment, the primary outcome occurred in 283 patients (10.3%). After adjustment for baseline characteristics (including baseline AF PROM score), improvement in the AF PROM overall summary score was associated with a lower risk of adverse outcomes (per 5-point increase: hazard ratio, 0.93 [95% CI, 0.89-0.96]; P < .001). CONCLUSIONS AND RELEVANCE: This cohort study of patients with AF in Japan found that greater improvements in 1-year AF PROM scores were associated with a lower risk of subsequent adverse clinical events. These findings support the prognostic value of PROMs and highlight the importance of monitoring health status in AF management.