Association between iron-deficiency anemia and obstructive sleep apnea: a systematic review and meta-analysis

Abstract

Obstructive sleep apnea (OSA) and iron-deficiency anemia (IDA) are prevalent conditions that may share underlying pathophysiological mechanisms, including intermittent hypoxia, systemic inflammation, and metabolic disturbances. However, whether a direct association exists between them remains unclear. To systematically assess the evidence for an association between IDA and OSA. We searched PubMed, Embase, Scopus, Web of Science, and the Cochrane Library from inception through August 2025. Observational and interventional studies examining the relationship between IDA and OSA were included. Two reviewers independently extracted data and assessed study quality using the Newcastle–Ottawa Scale. A random-effects meta-analysis was used to calculate pooled odds ratios (ORs) with 95% confidence intervals (CIs). Heterogeneity was evaluated using the I 2 statistic. Sensitivity analyses were performed to assess the robustness of the findings. Five studies comprising 1,963 participants were included in the qualitative synthesis; three provided data for the meta-analysis. IDA was associated with significantly higher odds of OSA (pooled OR = 1.66, 95% CI 1.27–2.17, p < 0.001), with no observed statistical heterogeneity (I 2 = 0%, p = 0.91). The 95% prediction interval ranged from 0.89 to 3.08. Leave-one-out sensitivity analysis demonstrated stable effect estimates (OR range: 1.52–1.78). Exclusion of the bariatric cohort did not materially change the pooled estimate (OR = 1.68, 95% CI 1.24–2.28). Qualitative synthesis consistently demonstrated lower ferritin levels and altered iron indices among patients with OSA. Iron-deficiency anemia is associated with higher odds of obstructive sleep apnea. Although the relationship appears consistent, causality remains uncertain. Larger prospective studies with standardized diagnostic criteria are needed to clarify the direction and clinical implications of this association.