New-Onset Atrial Fibrillation and Accelerated Kidney Function Decline in Working-Age Adults.

IMPORTANCE

Early identification of cardiovascular-kidney-metabolic (CKM) syndrome is essential for preventing subsequent organ failure. While atrial fibrillation (AF) is often incidentally detected in working-age adults and such detection is a risk for heart failure development, its specific impact on kidney function decline is yet to be elucidated in this young population.

OBJECTIVE

To investigate the association of new-onset AF with subsequent kidney function decline in working-age adults.

DESIGN, SETTING, AND

PARTICIPANTS

This retrospective cohort study was conducted using annual health screening records (serial electrocardiogram and estimated glomerular filtration rate [eGFR]) and insurance claims data from April 1, 2015, to March 31, 2023, in Japan. Participants included screening attendees aged 35 to 59 years (working-age population) in sinus rhythm without prior AF, cardiovascular comorbidities, or end-stage kidney disease. Data were analyzed from April 1, 2024, to November 1, 2025.

EXPOSURE: Individuals who developed new-onset AF during the annual screening interval were matched 1:5 to those who did not.

MAIN OUTCOMES: The primary outcome was annual rate of eGFR decline, estimated using linear mixed-effects models. The secondary outcome was a 30% or greater decline in eGFR from baseline, assessed using a Cox proportional hazards model.

RESULTS

Among 7 717 526 individuals with sinus rhythm at baseline, 141 060 adults were matched (mean [SD] age, 49.8 [6.6] years; 81.8% male; median [IQR] follow-up, 4.73 [3.50-6.22] years). New-onset AF was associated with a greater annual rate of eGFR decline (-1.23 [95% CI, -1.26 to -1.21] mL/min/1.73 m2) than that of individuals who did not develop AF (-0.94 [95% CI, -0.95 to -0.93] mL/min/1.73 m2), with a difference of -0.29 (95% CI, -0.32 to -0.26) mL/min/1.73 m2 (P < .001). Also, new-onset AF was associated with an increased incidence of a 30% or greater eGFR decline (hazard ratio, 2.91; 95% CI, 2.72-3.11; P < .001).

CONCLUSIONS AND RELEVANCE: In this retrospective cohort study of working-age adults, new-onset AF was associated with an acceleration in kidney function decline. Further investigation is warranted to clarify the impact of AF burden on the decline and to determine the effectiveness of AF treatments for improving kidney outcomes.