For all-cause mortality (Figure 6), while variables such as age, gender, education level, smoking, hypertension, diabetes, and cardiovascular comorbidities independently predicted mortality (p < 0.05 for main effects), only diabetes (p for interaction = 0.009), CHF (p for interaction = 0.02), and CKD (p for interaction < 0.001) significantly modified the cystatin C–mortality relationship. This evidence concerns the gene CST3 and chronic kidney disease.