GSTM1 and Iron deficiency anemia: HF: heart failure; Hb: hemoglobin; AHF: acute heart failure; CHF: heart failure; DM: diabetes mellitus; CKD: chronic kidney disease; CAD: coronary artery disease; COPD: chronic obstructive pulmonary disease; AF: atrial fibrillation; BNP: B-type natriuretic peptide; ID: iron deficiency; IDA: iron deficiency; HFpEF: heart failure with preserved ejection fraction; HFrEF: heart failure with reduced ejection fraction; NYHA: New York Heart Association; NM: not mentioned