Olfactory dysfunction and increased systemic immune inflammation index in patients with atrial fibrillation

Atrial fibrillation (AF) is a common arrhythmia with substantial morbidity and a need for accessible markers that reflect disease burden, while olfactory dysfunction and chronic inflammation may share overlapping vascular and neuroinflammatory pathways. We aimed to evaluate olfactory function in patients with AF and to explore the role of systemic inflammation using the systemic immune-inflammation index (SII). In this single-center case-control study, 85 consecutively enrolled adults (AF group, n = 43; control group, n = 42) underwent olfactory assessment with the Sniffin' Sticks Extended Test, including odor threshold (OT), odor discrimination (OD), and odor identification (OI), from which the threshold-discrimination-identification (TDI) score was derived; SII was calculated from same-day complete blood counts. Compared with controls, patients with AF had higher SII (878 [368-5769] vs. 503 [243-1450], p = 0.007) and lower OT (4 [1-8] vs. 5 [2-10], p = 0.001), OD (7 [4-12] vs. 13 [8-16], p < 0.001), OI (7.7 ± 2.6 vs. 12.6 ± 1.7, p < 0.001), and TDI scores (19 [10-29] vs. 29.5 [25-39], p < 0.001). Within the AF group, olfactory performance was inversely associated with symptom severity assessed by the European Heart Rhythm Association (EHRA) classification, and TDI was negatively correlated with SII. These findings indicate that AF is associated with impaired olfactory function and elevated systemic inflammation, supporting olfaction and inflammatory indices as potential correlates of symptom burden that warrant confirmation in larger prospective cohorts with standardized rhythm monitoring.