In all patients, after adjusting for age, sex, hypertension, and time to CT, the presence of the APOE ε4 allele (OR 2.020, 95% CI 1.064–3.834, p = 0.032) was associated with the island sign, whereas the presence of the APOE ε2 allele (OR 0.734, 95% CI 0.339–1.593, p = 0.435) was not. The gene discussed is APOE; the disease is Hypertension.