KL and chronic kidney disease: The association between serum Klotho concentration and all-cause and cardiovascular mortality was consistent in subgroups according to age (40–59 vs. 60–79 years old), sex, physical activity (meet the suggested guideline or not), smoking (never, former or current), obesity, diabetes, hypertension, CVD and CKD stages (stage 1–2 vs. stage 3–4).