Association Between Fractional Exhaled Nitric Oxide (FeNO) and Cognitive Function in Patients with Obstructive Sleep Apnea.

Purpose: Obstructive sleep apnea (OSA) is characterised by intermittent hypoxia and sleep fragmentation, both of which can impair cognition. This study aimed to investigate the association between fractional exhaled nitric oxide (FeNO), a non-invasive marker of airway inflammation, and memory performance in patients with OSA.

Methods: A total of 102 participants were enrolled: 62 with moderate or severe OSA (apnea-hypopnea index, AHI≥15) and 40 with snoring or mild OSA (AHI <15). Memory was assessed with the Rey-Osterrieth Complex Figure Test (RCFT), Digit Ordering Test (DOT), and Logical Memory Test (LMT). FeNO was measured at 50mL/s (FeNO₅₀) and 200mL/s (FeNO₂₀₀); alveolar NO (CaNO) was calculated. Group comparisions used t-tests and chi-square tests, cognitive scores employed mixed-design ANOVA, and associations were examined with Spearman correlation plus hierarchical regression.

Results: Compared with the snoring or mild OSA group, participants with moderate or severe OSA had larger neck circumference, higher body-mass index, greater daytime sleepiness, and elevated FeNO₅₀ and FeNO₂₀₀ (P < 0.05). They also showed poorer immediate and delayed visual memory (both P< 0.05), which correlated negatively with AHI (r = -0.088/-0.103, P < 0.05) and FeNO₅₀ (r = -0.286/-0.302, P < 0.05). RCFT scores fell over time (F = 271.171, P < 0.05), with a significant group × time interaction (F = 3.065, P < 0.05). FeNO₅₀ independently predicted poorer immediate recall (β = -0.28, P = 0.018), whereas FeNO₂₀₀ was not significant.

Conclusion: Moderate or severe OSA is associated with impaired immediate and delayed visual memory. Higher FeNO₅₀ correlates with memory decline, supporting a link between airway inflammation and cognitive dysfunction in OSA.