KL and rheumatoid arthritis: Klotho demonstrated a negative correlation with RA status across all 3 models (model 1: OR = 0.924, 95% CI: 0.862–0.991; model 2: OR = 0.923, 95% CI: 0.862–0.990; model 3: OR = 0.923, 95% CI: 0.861–0.991).