KL and Alzheimer disease: We aimed to assess whether KL-VS heterozygosity, cerebrospinal fluid (CSF) and serum soluble α-Klotho (sαKl) levels, would be associated with a lower likelihood of AD and better performance on memory and other cognitive domains in individuals with AD dementia, amnestic mild cognitive impairment (aMCI) due to AD, and cognitively unimpaired controls.