KL and chronic kidney disease: Data from the National Health and Nutrition Examination Survey (NHANES) collected between 2007 and 2016 (in most studies) revealed non-linear associations of the Klotho serum level with all-cause mortality, systemic inflammation index, accelerated aging, metabolic syndrome, hyperlipidemia, frailty, chronic kidney disease and cancer [17,264,265,266,267,268,269,270,271].