Because cystatin C appears to be more sensitive in detecting mild to moderate decrease in glomerular filtration rate [18, 19], shows strong associations with incident cardiovascular events [20] and all cause mortality [20, 21], and is not affected by age, gender, ethnicity, or muscle mass, this study focused on CKD defined by reduced GFR using a cystatin C-based estimating equation [22]. The gene discussed is CST3; the disease is chronic kidney disease.