Median plasma Klotho levels were significantly higher in men than women in the AD-dementia group (men, 871.4 pg/mL [range, 568.7-1027.9 pg/mL]; women, 711.9 pg/mL [range, 568.7-1027.9 pg/mL]; P = .04) but not in the other clinical groups. This evidence concerns the gene KL and Alzheimer disease.