The Bidirectional Relationship Between Iron Deficiency Anemia and Chronic Headache Disorders: A Systematic Review and Meta-Analysis.

IDA and chronic headache disorders such as migraines and tension-type headaches are common conditions that significantly affect quality of life. Emerging evidence suggests a bidirectional relationship between these two conditions. This systematic review and meta-analysis aimed to explore and quantify the association between iron deficiency anemia (IDA) and chronic headache disorders, with a focus on understanding the bidirectional nature of this relationship. A comprehensive literature search was conducted across PubMed, Embase, and Web of Science to identify relevant studies published up until August 10, 2024. Observational studies examining the prevalence, incidence, or association between IDA and chronic headache disorders were included. Data were extracted and assessed for quality using the Newcastle-Ottawa Scale. Meta-analyses were performed using a random-effects model to calculate pooled prevalence rates and risk ratios (RRs), with heterogeneity assessed via the statistic and meta-regression. A sensitivity analysis was conducted using the leave-one-out approach, and publication bias was evaluated through a funnel plot. The meta-analysis included 13 studies: five studies examined chronic headaches among patients with IDA, and eight studies examined IDA among patients with chronic headaches. The pooled prevalence of chronic headaches among patients with IDA was 38% (95% CI: 15%-69%). In addition, 20% (95% CI: 10%-35%) of patients with chronic headaches were found to have IDA. Anemic patients were found to have a 76% higher risk of developing chronic headaches compared to nonanemic individuals (RR: 1.76; 95% CI: 1.22-2.52). Significant heterogeneity was observed across the studies. This meta-analysis demonstrates a significant association between IDA and chronic headache disorders, with a pooled prevalence of 38% for chronic headaches in IDA patients and 20% for IDA in chronic headache patients. IDA was associated with a 76% higher risk of chronic headaches. Routine screening for IDA in high-risk populations may improve headache outcomes, but further longitudinal studies are needed to establish causality and refine management strategies.