Glycemic risk stratification in older adults with heart failure: the prognostic role of HbA1c in an aging society

Glycated haemoglobin (HbA1c) is central to diabetes mellitus (DM) management, but its prognostic value in older adults, aged ≥80 years, with heart failure (HF) remains uncertain. Thus, the study aimed to evaluate the association between HbA1c levels and all-cause mortality among adults aged ≥80 years with newly diagnosed HF. This retrospective cohort study included 5300 adults aged ≥80 years with a first diagnosis of HF and an HbA1c measurement within ±3 months of HF diagnosis between 2009 and 2025. Patients were categorized by HbA1c as normal (< 5.7%), prediabetes range (5.7%-6.4%), DM range (6.5%-<7.2%), and elevated HbA1c range (≥ 7.2%). The primary outcome was all-cause mortality. Cox proportional hazards models evaluated the association between HbA1c category and mortality, adjusted for age, sex, comorbidities, left ventricular ejection fraction, systolic pulmonary artery pressure, glomerular filtration rate and body mass index. The cohort included 5300 adults, consisting of 1714 (32.3%) with normal HbA1c, 1928 (36.4%) with prediabetes-range HbA1c, 786 (14.8%) with DM-range HbA1c, and 872 (16.5%) with HbA1c ≥7.2%. Among 3541 participants with DM, 2571 (72.6%) were not treated with insulin. Median age was 85 years, and 54% were male. During a median follow-up of 2.73 years, 3888 patients died. Each 1% increase in HbA1c was associated with higher mortality in the overall cohort (HR 1.03; 95% CI 1.01–1.05; P=.003), particularly among patients with DM not treated with insulin (HR 1.04; 95% CI 1.02–1.07; P<.001). Compared with normal HbA1c, prediabetes-range HbA1c and DM-range HbA1c were not associated with mortality. Elevated HbA1c was independently associated with higher mortality risk (HR 1.28; 95% CI 1.16–1.42; P<.001). Associations were observed across several clinically relevant subgroups, without significant interaction. Among adults aged ≥80 years with HF, HbA1c retained clinically meaningful prognostic value only at higher levels. An HbA1c threshold of ≥7.2% identified a distinct high-risk phenotype with significantly worse outcomes, despite the high burden of multimorbidity characteristic of this age group. Key words: Heart failure; Glycated hemoglobin; HbA1c; Older adults ; Risk stratification