Splenic enlargement as a physiologic adaptation to obstructive sleep apnea and nocturnal hypoxemia: A retrospective cohort study.

STUDY

OBJECTIVES

We sought to determine whether spleen volume is increased in patients with obstructive sleep apnea (OSA) and whether splenic enlargement correlates with disease severity, translating adaptive physiologic responses observed in diving and high-altitude populations to a clinical sleep disorder.

METHODS

We retrospectively analyzed 50 adults with OSA (AHI ≥5) who underwent abdominal computed tomography (CT) prior to sleep study at a single tertiary care center. Spleen volume was measured using the prolate ellipsoid formula by two blinded reviewers. OSA severity metrics (apnea-hypopnea index [AHI], oxygen desaturation index [ODI], SpO2 nadir, and percent time with oxygen saturation <90%) were extracted from polysomnography or home sleep apnea testing. Multivariate linear regression models assessed associations between log-transformed spleen volume and OSA severity, adjusting for demographic and clinical covariates.

RESULTS

Log-transformed ODI (Estimate = 0.28, 95% CI: 0.08-0.49, p = 0.008) and log AHI (Estimate = 0.29, 95% CI: 0.08-0.49, p = 0.007) were significantly associated with increased spleen size. Percent time under 90% SpO2 was also a significant predictor (Estimate = 0.12, 95% CI: 0.04-0.21, p = 0.006). Age demonstrated a negative association with spleen volume. In reverse models, log spleen size predicted OSA severity metrics, supporting bidirectionality of the relationship.

CONCLUSIONS

Spleen size is positively associated with clinical markers of OSA severity, suggesting that chronic intermittent hypoxemia may induce splenic adaptation. Spleen size may serve as a novel, pragmatic biomarker for OSA severity. Further study is warranted to clarify clinical significance.