Abstract Purpose Heart failure and atrial fibrillation (AF) frequently complicate one another. Risk of heart failure in screen-detected patients was not investigated. We aimed to compare risk of hospitalization for heart failure (HHF) between screen-detected and clinically-diagnosed AF, and to evaluate the impact of AF burden. Methods Consecutive patients aged over 65 attending outpatient clinics were prospectively recruited for AF screening, using handheld single-lead ECG (AliveCor) during December 2014 and December 2017. Patients who had >1 visits received repeat screening. All participants were divided into 5 cohorts: (i) previously known AF at enrolment; (ii) initial screen-detected AF; (iii) subsequent screen-detected AF; (iv) clinically-diagnosed AF during follow-up (FU); (v) No AF. Risk of HHF was estimated by adjusted sub-distribution hazard ratios (aSHR) derived from Fine and Gray regression, accounting for death as competing risk, adjusting for CHA2DS2VASC components and chronic kidney disease, AF diagnosis being handled as time-dependent variable. Patients who participated in repeat screening and previously known AF formed a sub-cohort. Patients with previously known AF who were in AF in the initial screening and those with repeat screen-positivity were defined probably persistent AF, otherwise paroxysmal AF (single screen-positivity) or no AF (never screen-positive). Risk of HHF was compared between groups stratified by AF burden (persistent vs. paroxysmal) and scenario of AF diagnosis (screen-detected vs. clinically-diagnosed). Results Of 11,972 subjects (mean age 76.6±7.8, female 49.2%), 18.7% (n=2,236) had known AF, 1.9% (n=223) initial screen-detected AF, 0.6% (n=71) subsequent screen-detected AF, 7.3% (n=867) clinically-diagnosed AF during FU, and 71.6% (n=8,559) no AF. During a median FU of 6.7 (IQR:4.4-8.0) years, risk of HHF was highest in patients with clinically-diagnosed AF (aSHR=3.5(2.7-4.5)), followed by subsequent screen-detected AF (aSHR=2.8(1.6-5.0)), previously known AF (aSHR=1.9(1.6-2.2)), and initial screen-detected AF (aSHR=1.7(1.1-2.4)) (Figure 1a). Sensitivity analysis excluded those with known heart failure at baseline, after which risk of HHF became comparable between previously known and initial screen-detected AF (Figure 1b). Sub-analysis for participants (32.2% (n=3,853), mean age 76.7±7.3, female 47.5%) of repeat screening showed screen-detected persistent AF (aSHR=3.7(1.9-7.2)) was at highest risk of HHF, followed by clinically-diagnosed AF (AF burden unassessed) (aSHR=3.3(2.2-5.0)), previously known persistent AF (aSHR=3.1(2.5-3.8)), screen-detected paroxysmal AF (aSHR=2.1(1.4-3.4)), previously known paroxysmal AF (aSHR=1.8(1.3-2.4) (Figure 1c). Conclusion Higher AF burden and FU new AF diagnosed by either screening or clinic visit was associated with higher risk of HHF. Screening facilitating early AF diagnosis and early downstream intervention, warranted further study.