Further, COMT alleles have been associated with specific cerebrospinal fluid (CSF) biomarkers of AD, with lower CSF amyloid-β42 in Val/Val carriers but higher t-tau and p-tau181 in Met/Met carriers compared to Val/Met, suggesting that those with heterozygous alleles may have protection against AD (Babić Leko et al., 2020). This evidence concerns the gene COMT and Alzheimer disease.