A subgroup analysis for all-cause mortality that was based on sex, age, ethnicity, BMI, eGFR, and 25-hydroxyvitamin D found that high serum klotho concentrations were more beneficial among RA patients who were white, older than 60 years, and with a BMI of < 25 kg/m2 and 25-hydroxyvitamin D level of ≥ 50 nmol/L. Here, KL is linked to rheumatoid arthritis.