Time-Varying Association of Individual BP Components with eGFR in Late-Stage CKD

Effect of blood pressure trajectory and variability on new-onset chronic kidney disease in patients with type 2 diabetes

This study aimed to evaluate the effects of BP trajectory and variability on chronic kidney disease (CKD) incidence in patients with type 2 diabetes. This retrospective longitudinal study included 4,560 participants with type 2 diabetes, aged ≥30 years, free of CKD, with ≥3 years of follow-up, and who attended the Diabetes Care Management Program in 2001-2013. The follow-up period ended in 2016. The adverse outcome was a new-onset CKD event, which was determined using eGFR and albuminuria. Cox proportional hazards models were used to assess the associations. At the end of the follow-up, 1255 participants had developed CKD, with a mean follow-up of 4.3 ± 3.2 years. Three trajectory subgroups of BP, i.e., Cluster 1: "moderate-stable" for SBP and "moderate-downward" for DBP, Cluster 2: "low-upward-downward" for both SBP and DBP, and Cluster 3: "high-downward-upward" for both SBP and DBP, were generated. The BP variability was grouped into three classes on the basis of tertiles. For the BP trajectory, patients in Cluster 3 of DBP had a higher CKD risk than those in Cluster 1 (HR = 1.24, 95% CI = 1.03-1.50). For the BP variability, patients in Tertile 3 had a significantly higher CKD risk than those in Tertile 1 (SBP: 1.28, 1.11-1.47; DBP: 1.17, 1.02-1.34). Persons with type 2 diabetes who achieved a small reduction in DBP after participating in the education program but rebounded and those who had the highest variation in both SBP and DBP faced the highest increase in CKD risk.

Systolic blood pressure and chronic kidney disease progression in patients with primary glomerular disease

INTRODUCTION

Many current guidelines on optimal target blood pressure (BP) for chronic kidney disease (CKD) patients are largely based on studies in diabetic and hypertensive patients. However, there have been few studies in patients with glomerular diseases.

METHODS

We retrospectively studied the longitudinal association between BP and CKD progression in 1,066 biopsy-proven patients diagnosed with primary glomerular diseases, including IgA nephropathy, membranous nephropathy (MN), and focal segmental glomerulosclerosis (FSGS), between 2005 and 2017. The main predictor was time-updated systolic blood pressure (SBP) at every clinic visit. The primary outcome was a composite one including ≥ 50% decrease in estimated glomerular filtration rate (eGFR) from the baseline, and end-stage kidney disease (ESKD).

RESULTS

During 5009 person-years of follow-up, the primary outcome occurred in 157 (14.7%) patients. In time-varying Cox model, the adjusted hazard ratios (HRs) (95% confidence interval (CI)) for the primary outcome were 1.48 (0.96-2.29), 2.07 (1.22-3.52), and 2.53 (1.13-5.65) for SBP of 120-129, 130-139, and ≥ 140 mmHg, respectively, compared with SBP < 120 mmHg. This association was particularly evident in patients with elevated proteinuria. However, there was no association between baseline SBP and adverse kidney outcomes. Finally, prediction models failed to show the improvement of predictive performance of SBP compared with that of remission status. Moreover, patients with remission and less controlled SBP had better kidney outcomes than those with non-remission and well-controlled SBP.

CONCLUSION

Among patients with glomerular disease, higher time-updated SBP was significantly associated with higher risk of CKD progression. However, the clinical significance of blood pressure was less powerful than remission status.

Trajectory of extracellular fluid volume over time and subsequent risks of end-stage kidney disease and mortality in chronic kidney disease: a prospective cohort study

BACKGROUND

Extracellular fluid volume (ECF) is independently associated with chronic kidney disease (CKD) progression and mortality in patients with CKD, but the prognostic value of the trajectory of ECF over time beyond that of baseline value is unknown.

OBJECTIVES

To characterize ECF trajectory and evaluate its association with the risks of end-stage kidney disease (ESKD) and mortality.

METHODS

From the prospective tricentric NephroTest cohort, we included 1588 patients with baseline measured glomerular filtration rate (mGFR) ≥15 mL min^-1 /1.73 m² and ECF measurement. ECF and GFR were measured repeatedly using the distribution volume and clearance of ⁵¹ Cr-EDTA, respectively. ESKD and mortality were traced through record linkage with the national registries. Adjusted shared random-effect joint models were used to analyse the association between the trajectory of ECF over time and the two competing outcomes.

RESULTS

Patients were mean age 58.7 years, 66.7% men, mean mGFR of 43.6 ± 18.6 mL min^-1 /1.73 m² and mean ECF of 16.1 ± 3.6 L. Over a median follow-up of 5.3 [IQR: 3.0;7.4] years, ECF increased by 136 [95%CI 106;167] mL per year on average, whilst diuretic prescription and 24-hour urinary sodium excretion remained stable. ESKD occurred in 324 (20.4%) patients, and 185 (11.6%) patients died before ESKD. A higher current value of ECF was associated with increased hazards of ESKD (adjusted hazard ratio [aHR]: 1.12 [95%CI 1.06;1.18]; P < 0.001 per 1 L increase in ECF), and death before ESKD (aHR: 1.10 [95%CI 1.04;1.17]; P = 0.002).

CONCLUSIONS

The current value of ECF was associated with the risks of ESKD and mortality, independent of multiple potential confounders, including kidney function decline. This highlights the need for a close monitoring and adjustment of treatment to avoid fluid overload in CKD patients.

Pitfalls of linear regression for estimating slopes over time and how to avoid them by using linear mixed-effects models

Clinical epidemiological studies often focus on investigating the underlying causes of disease. For instance, a nephrologist may be interested in the association between blood pressure and the development of chronic kidney disease (CKD). However, instead of focusing on the mere occurrence of CKD, the decline of kidney function over time might be the outcome of interest. For examining this kidney function trajectory, patients are typically followed over time with their kidney function estimated at several time points. During follow-up, some patients may drop out earlier than others and for different reasons. Furthermore, some patients may have greater kidney function at study entry or faster kidney function decline than others. Also, a substantial heterogeneity may exist in the number of kidney function estimates available for each patient. This heterogeneity with respect to kidney function, dropout and number of kidney function estimates is important to take into account when estimating kidney function trajectories. In general, two methods are used in the literature to estimate kidney function trajectories over time: linear regression to estimate individual slopes and the linear mixed-effects model (LMM), i.e. repeated measures analysis. Importantly, the linear regression method does not properly take into account the above-mentioned heterogeneity, whereas the LMM is able to retain all information and variability in the data. However, the underlying concepts, use and interpretation of LMMs are not always straightforward. Therefore we illustrate this using a clinical example and offer a framework of how to model and interpret the LMM.

Blood pressure parameters and morbid and mortal outcomes in nondialysis-dependent chronic kidney disease

PURPOSE OF REVIEW

Observational and interventional studies provide conflicting evidence regarding optimal blood pressure (BP) control in persons with chronic kidney disease (CKD). Recent publications provide additional information to inform therapeutic decision-making.

RECENT FINDINGS

Targeting SBP to less than 120 mmHg, versus less than 140 mmHg, decreased cardiovascular events and all-cause mortality in persons with nondiabetic CKD. A meta-analysis of trials testing blood pressure management among nondialysis-dependent CKD patients (15 924 total patients) found more intensive therapies generally reduced mortality in all subgroups. Observational studies demonstrate that low SBP is associated with higher mortality in CKD. A recent report suggests that this is because of death from cardiovascular and noncardiovascular and nonmalignant causes, whereas higher BP is associated with death from cardiovascular causes. The shape of association between BP and cardiovascular and noncardiovascular events also appears to vary depending on baseline risk factors. Furthermore, BP measurement methodology may differ importantly between observational and interventional studies.

SUMMARY

We review and summarize observational and interventional literature relating BP parameters to key clinical outcomes in persons with CKD. Apart from the inherent differences between these study designs, the disparate findings from trials and observational studies may be because of differences in patient characteristics and BP measurement techniques.