BackgroundThis ANAFIE Registry sub-analysis investigated 2-year outcomes and oral anticoagulant (OAC) use stratified by glycated hemoglobin (HbA1c) levels among Japanese patients aged ≥ 75 years with non-valvular atrial fibrillation (NVAF) with and without clinical diagnosis of diabetes mellitus (DM).MethodsThe ANAFIE Registry was a large-scale multicenter, observational study conducted in Japan; this sub-analysis included patients with baseline HbA1c data at baseline. The main endpoints evaluated (stroke/systemic embolic events [SEE], major bleeding, intracranial hemorrhage, cardiovascular death, all-cause death, and net clinical outcome [a composite of stroke/SEE, major bleeding, and all-cause death]) were stratified by HbA1c levels (< 6.0%; 6.0% to < 7.0%; 7.0% to < 8.0%; and ≥ 8.0%).ResultsOf 17,526 patients with baseline HbA1c values, 8725 (49.8%) patients had HbA1c < 6.0%, 6700 (38.2%) had 6.0% to < 7.0%, 1548 (8.8%) had 7.0% to < 8.0%, and 553 (3.2%) had ≥ 8.0%. Compared with other subgroups, patients with HbA1c ≥ 8.0% were more likely to have lower renal function, higher CHA2DS2-VASc and HAS-BLED scores, higher prevalence of non-paroxysmal AF, and lower direct OAC (DOAC) administration, but higher warfarin administration. The HbA1c ≥ 8.0% subgroup had higher event rates for all-cause death (log-rankP= 0.003) and net clinical outcome (log-rankP= 0.007). Similar trends were observed for stroke/SEE. In multivariate analysis, risk of all-cause death (adjusted hazard ratio [aHR]: 1.46 [95% confidence interval 1.11–1.93]) and net clinical outcome (aHR 1.33 [1.05–1.68]) were significantly higher in the HbA1c ≥ 8.0% subgroup. No significant differences were observed in risks of major bleeding or other outcomes in this and other subgroups. No interaction was observed between HbA1c and OACs. Use/non-use of antidiabetic drugs was not associated with risk reduction; event risks did not differ with/without injectable antidiabetic drugs.ConclusionsAmong elderly Japanese patients with NVAF, only HbA1c ≥ 8.0% was associated with increased all-cause death and net clinical outcome risks; risks of the events did not increase in other HbA1c subgroups. Relative event risks between patients treated with DOACs and warfarin were not modified by HbA1c level.Trial registrationUMIN000024006; date of registration: September 12, 2016.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12933-023-01915-3.