Luo et al. (2015) reported that individuals with mild cognitive impairment have much higher methylation levels of klotho promoter. One study conducted in aging Caucasian individuals without dementia or cognitive complaints revealed that a haplotype and functional variant of the KLOTHO gene, KL-VS, was common in these populations, and the KL-VS allele was associated with increased serum klotho levels and better cognitive performance (Dubal et al., 2014). Similarly, Deary et al. (2005) showed that people with the KLOTHO V/V genotype had lower cognitive ability than those with the heterozygotes. Here, KL is linked to dementia.