Among APOE‐ε4 non‐carriers, patients with Alzheimer's disease in the highest PRS quintile had 4.1 years younger age of onset of disease (p = 0.0002) compared to patients in bottom quintiles, but only 0.43 years in APOE‐ε4 carriers. The gene discussed is APOE; the disease is early-onset autosomal dominant Alzheimer disease.