Clinically, there are various factors: 1. physiological hypo-hematopoiesis in the elderly 2. nutritional factors: the change of diet structure produces many “diseases of modern civilization”, and inappropriate dietary restrictions to prevent these diseases cause anemia 3. secondary anemia: caused by non-hematopoietic diseases such as malignant tumors, liver diseases, chronic renal insufficiency, chronic infections, endocrine abnormalities, etc. chronic renal insufficiency, chronic infection, endocrine abnormalities, etc. 4.Environmental factors: Environmental pollution factors are important, and the elderly are more sensitive to them.