In a subsequent study by the same authors of 20 patients with high- and low-grade gliomas stratified according to whether or not they harbored the APOE ε-4 allele, a battery of cognitive tests were administered at two time points: first, a mean of 4 years after completing treatment, and second a mean 5.21 years later (126). The gene discussed is APOE; the disease is glioma.