Another study on the relationship between HRR and cognitive dysfunction after stroke found that patients with decreased HRR levels had an increased risk of cognitive dysfunction, and the two showed a negative linear relationship (18), and in a cross-sectional study on the ratio of hemoglobin to red blood cell distribution width and depression in older adults, it was shown that HRR may be an independent risk factor for depression, being more powerful than Hb or RDW alone. The gene discussed is GSTM1; the disease is major depressive disorder.