Prolonged QTc is a major risk factor for ventricular arrhythmias and sudden cardiac death (SCD). Anaemia’s impact on the QT interval is unclear and conflicting despite its association with increased mortality.

We investigated the association between anaemia and the prevalence of QTc prolongation, as well as potential gender differences in this relationship. Additionally, we examined whether haemoglobin levels were associated with QTc prolongation.

Observational cross-sectional study.

Sheshdeh, Fasa, Iran.

We analysed data from 5741 participants from the general population (aged 35–70 years) with no history of ischaemic heart disease; myocardial infarction; amiodarone use; multiple blood transfusions; or supplementation with iron, folic acid or cobalamin.

Anaemia was defined according to WHO guidelines (haemoglobin 450 ms in men or >470 ms in women.

Among 5741 participants, mean QTc was 427.91±24.75 ms, with QTc prolongation in 7.14%. Anaemia raised the odds of QTc prolongation by 60% (OR=1.60, 95%CI 1.12 to 2.28, p=0.010), particularly in females (OR=1.73, 95%CI 1.12 to 2.66, p=0.013), but not in males. Higher haemoglobin levels were associated with lower QTc prolongation risk (OR=0.91 per unit increase, 95% CI 0.85 to 0.97, p=0.005). No significant associations were observed between anaemia type/severity and QTc prolongation among anaemic individuals.

Anaemia was significantly associated with QTc prolongation, particularly in females. Anaemia type/severity did not affect QTc prolongation. Anaemia is associated with increased odds of QTc prolongation, particularly in women. While causality cannot be inferred from this cross-sectional analysis, the findings suggest that clinicians may consider QTc monitoring in anaemic patients, especially women and exercise caution when prescribing QT-prolonging medications. Prospective studies are needed to confirm whether anaemia directly contributes to QTc prolongation or arrhythmic risk.