Evidence check: APOE in the context of fatigue

The APOE variant (especially ε4) is primarily linked to lipid metabolism and Alzheimer's risk, not directly to fatigue. There is weak mechanistic evidence that ε4 might indirectly contribute to exhaustion via increased inflammation or impaired mitochondrial function, but findings are inconsistent and not clinically actionable. Fatigue is multifactorial; common causes include iron deficiency, sleep disorders, thyroid dysfunction, and stress. A genetic test alone does not guide therapy. Before any supplementation or intervention, get blood markers (ferritin, CRP, TSH, vitamin D) evaluated by a clinician. The provided context does not include APOE-specific fatigue studies; this assessment is based on general literature. Evidence: mechanistic/unclear.