Cognitive Impairments in Iron Deficiencies in Adults: A Systematic Review

Background. Iron deficiency (ID) is the leading cause of anaemia worldwide and a potentially significant risk factor for cognitive impairment in adults. Despite accumulating evidence, systematic data on the effects of iron-deficient states on cognitive functioning in the adult population remain limited. The objective of this review was to systematically analyse original clinical studies published over the past five years examining cognitive impairment in adults with iron deficiency anaemia (IDA) and ID without anaemia.

Methods. Original studies were included if they enrolled adults (≥18 years) with a laboratory-confirmed diagnosis of IDA or ID according to WHO criteria and assessed cognitive function using validated neuropsychological instruments (MMSE, MoCA, WAIS-IV, Digit Span, etc.); studies conducted in paediatric populations were excluded. Searches were performed in PubMed, Google Scholar, and eLibrary, supplemented by manual reference screening. Methodological quality was assessed using the Newcastle–Ottawa Scale by two independent reviewers. Given the heterogeneity of study designs, a narrative synthesis approach was applied.

Results. Of 294 identified publications, 9 studies met the inclusion criteria. All included studies demonstrated a significant association between IDA/ID and impairment of memory, attention, information processing speed, and executive function. The severity of cognitive deficit correlated with the degree of anaemia. Neurophysiological and neuroimaging data (event-related potentials, resting-state fMRI) confirmed functional impairment of the central nervous system. Available evidence on the efficacy of iron supplementation suggests that cognitive deficits are reversible with timely treatment.

Discussion. The findings are consistent with the existing body of evidence and indicate that cognitive impairment associated with iron deficiency may be reversible when treatment is initiated promptly. Prospective randomised studies employing standardised cognitive assessment protocols are warranted. Limitations of this review include the predominance of cross-sectional studies with small sample sizes, heterogeneity of diagnostic criteria and neuropsychological instruments, and a limited number of interventional studies.