Association of iron deficiency anemia with tuberculosis in Taiwan: A nationwide population-based study

Background Iron deficiency is associated with decreased cellular immunity, which may predispose patients with iron deficiency anemia (IDA) to increased risk of developing tuberculosis (TB). This study investigated the relationship between newly diagnosed IDA and TB infection in Taiwan. Methods The study included data on 21,946 patients with incident IDA and 87,555 non-IDA controls from a national database covering the period 2000-2012. IDA and non-IDA subjects were matched 1: 4 on age, gender, and index year. The follow-up period was defined as the time from the initial IDA diagnosis to the date of developing TB or 31 December 2013. Cox proportional hazards models were used to estimate hazard ratios and 95% confidence intervals, with the control group as the reference. Results The adjusted hazard ratio of TB for the IDA group was 1.99 (95% confidence interval, 1.77-2.25) compared with the control group. The subgroup analysis showed that for both genders, all age groups, and patients with diabetes mellitus, hyperlipidemia, hypertension, cancer, chronic obstructive pulmonary disease, and hepatitis B virus infection, the IDA group had significantly higher TB incidence. The association was significantly stronger within the 5 years after new IDA diagnosis for both genders and all age groups. Conclusions Higher TB incidence was discovered in the IDA group, especially for patients with comorbidities.