Risk of Iron Deficiency in Women With Endometriosis: A Population-Based Prospective Cohort Study

Background Endometriosis may be linked to the risk of iron deficiency through chronic systemic inflammation or heavy menstrual bleeding. No longitudinal studies, however, have examined the relationship between endometriosis and the risk of iron deficiency. Methods This study included 3,294 participants born from 1973 to 1978 and followed as part of the Australian Longitudinal Study on Women's Health from 2000 to 2018. Participants with endometriosis were identified using self-reported longitudinal surveys linked to administrative health records. During each survey, participants were also asked to report the diagnosis of iron deficiency, and we validated diagnoses using an administrative health database. Generalized estimating equations for binary responses with an autoregressive correlation matrix were used to examine the association between endometriosis and the risk of iron deficiency over the seven time points. Findings We found that women with endometriosis had a significantly higher risk of iron deficiency than those without endometriosis after adjusting for sociodemographic, lifestyle, reproductive, and nutrition factors (adjusted odds ratio [aOR] = 1.46; 95% confidence interval [CI] [1.29, 1.66]; p < .0001). Women with a surgically confirmed diagnosis and those with clinically suspected endometriosis had a higher risk of iron deficiency (aOR = 1.38; 95% CI [1.17, 1.64] and aOR = 1.53; 95% CI [1.30, 1.81]), respectively. These associations, however, were slightly attenuated (by 8%) when adjusted for the presence of heavy menstrual bleeding. Conclusions Women with endometriosis are at a higher risk of developing iron deficiency than those without endometriosis. The findings suggest that iron deficiency should be concomitantly addressed during initial diagnosis and successive management of endometriosis.