KL and chronic kidney disease: Consistently, Klotho levels in humans decline with age and age-related diseases, such as chronic kidney disease (Kuro-o, 2019; Mattinzoli et al., 2023), and reductions in Klotho levels are associated with worse cognition in older people (Shardell et al., 2016; Yokoyama et al., 2017; Kundu et al., 2022; Wu et al., 2023; Ge et al., 2024) and an increased risk of all-cause mortality (Prud’homme et al., 2022).