Anemia and Sleep Disturbances: Mechanisms, Evidence and Clinical Implications - a Narrative Review

Anemia, particularly iron deficiency anemia (IDA), is the most common subtype, which affects over two billion individuals worldwide and is associated with various sleep disturbances in both observational and interventional studies. Although there is a growing attention towards this connection, its mechanisms, extent and treatability of have not been thoroughly investigated.

This narrative review assesses the relationship between anemia, including iron deficiency anemia (IDA) and non-IDA subtypes, and various sleep-related outcomes, such as subjective sleep quality, objective sleep architecture, total sleep duration, sleep latency, sleep efficiency, restless legs syndrome (RLS), periodic limb movements (PLMs), insomnia and sleep-disordered breathing across different age groups and populations.

We performed searches in PubMed/MEDLINE, Embase, Scopus, Web of Science and the Cochrane Library from the foundation of these databases until February 2026, without any language constraints. Eligible study formats encompassed cross-sectional surveys, prospective cohorts, case-control studies, randomized controlled trials (RCTs) of iron therapy that reported sleep outcomes, as well as current systematic reviews and meta-analyses. The synthesis was predominantly narrative due to significant variation among studies regarding anemia definitions, sleep assessment methodologies and population characteristics.

Iron deficiency anemia is consistently linked to decreased sleep quality (higher Pittsburgh sleep quality index [PSQI] scores), reduced total sleep duration, extended sleep-onset latency, lower sleep efficiency and decreased slow-wave sleep. Restless legs syndrome (RLS) significantly manifests more often in IDA individuals, with ferritin levels of 50-75 µg/L being identified as clinically pertinent indicators. Iron supplementation, whether oral or intravenous, significantly decreases RLS severity scores and sleep disturbances in most of the assessed RCTs (moderate-certainty evidence).

The existing evidence suggests a clinically relevant link between anemia -particularly IDA - and numerous sleep disorders, with RLS being the most typical and iron-responsive symptom. Iron repletion is a viable mechanism-based treatment for IDA-related sleep disorders.