Nonlinear association between proteinuria levels and the risk of cardiovascular disease events and all-cause mortality among chronic kidney disease patients

Background: The association between proteinuria levels and cardiovascular disease (CVD) development and all-cause mortality in chronic kidney disease (CKD) patients remains controversial. Methods: In this investigation, we conducted a retrospective analysis involving 1138 patients who were registered in the CKD-Research of Outcomes in Treatment and Epidemiology (ROUTE) study. The primary outcome of this study was the composite of cardiovascular events or all-cause death. Cox proportional hazards regression, smooth curve fitting, piecewise linear regression, and subgroup analyses were used. Results: The mean age of the included individuals was 67.3 +/- 13.6 years old. Adjusted hazard ratios (HRs) for UPCR in middle and high groups, compared to the low group, were 1.93 (95% CI: 1.28-2.91) and 4.12 (95% CI: 2.87-5.92), respectively, after multivariable adjustment. Further adjustments maintained significant associations; HRs for middle and high groups were 1.71 (95% CI: 1.12-2.61) and 3.07 (95% CI: 2.08-4.54). A nonlinear UPCR-primary outcome relationship was observed, with an inflection point at 3.93 g/gCr. Conclusion: Among non-dialyzed patients with stage G2-G5 CKD, a nonlinear association between UPCR and the primary outcome was observed. A higher UPCR (when UPCR < 3.93 g/gCr) was an independent predictor of the primary outcome. Importantly, our study predates SGLT2 inhibitor use, showcasing outcomes achievable without these medications. Future research considerations will involve factors like SGLT-2 inhibitor utilization.