Chronic Disease Anemia: This is often seen in patients with chronic conditions such as vascular dementia. The body's chronic inflammatory state can lead to a decrease in erythropoietin production and a relative resistance to erythropoietin, resulting in anemia. The patient's few weeks of fatigue without overt bleeding also support this diagnosis.

Anemia of Renal Insufficiency: Given the patient's age and vascular dementia, renal insufficiency is a possibility. Decreased renal function can lead to a decrease in erythropoietin production, causing anemia.
Medication-Induced Anemia: The patient may be taking medications that can cause anemia, such as antihypertensives, anti-inflammatory drugs, or other medications commonly used in patients with vascular dementia.
Nutritional Deficiencies: Deficiencies in vitamins and minerals such as vitamin B12, folate, or iron can cause anemia, although normocytic anemia is less common in these cases.

Gastrointestinal Cancer: Although less likely, gastrointestinal cancer can cause anemia due to chronic blood loss. Given the patient's age, it is essential to rule out this possibility.
Hematologic Malignancies: Leukemia, lymphoma, or myelodysplastic syndromes can cause anemia and are critical to diagnose early.
Acute Blood Loss: Although the patient reports no overt bleeding, it is essential to consider the possibility of internal bleeding, which may not be immediately apparent.

Autoimmune Hemolytic Anemia: This condition is characterized by the immune system attacking and destroying red blood cells, leading to anemia.
Paroxysmal Nocturnal Hemoglobinuria (PNH): A rare, acquired, life-threatening disease of the blood characterized by the destruction of red blood cells.
Inherited Disorders: Such as hereditary spherocytosis or other rare genetic disorders that can cause anemia.