Height constitutes an important predictor of mortality in end-stage renal disease

Height at First RRT and Mortality in Children

BACKGROUND AND OBJECTIVES

Poor linear growth is common in children with CKD and has been associated with higher mortality. However, recent data in adult dialysis patients have suggested a higher risk of death in persons of tall stature. In this study, we aimed to examine the risk of all-cause and cause-specific mortality in children at both extremes of height at the time of first RRT.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using the US Renal Data System, we performed a retrospective analysis of 13,218 children aged 2-19 years, who received their first RRT (dialysis or transplant) during 1995-2011. We used adjusted Cox models to examine the association between short (<3rd percentile) and tall (>3rd percentile) stature and risk of death, compared with less extreme heights.

RESULTS

Over a median follow-up of 7.1 years, there were 1721 deaths. Risk of death was higher in children with short (hazard ratio, 1.49; 95% confidence interval, 1.33 to 1.66) and tall stature (hazard ratio, 1.32; 95% confidence interval, 1.03 to 1.69) in adjusted analysis. In secondary analyses, there was a statistically significant interaction between height and body mass index categories (P=0.04), such that the association of tall stature with higher mortality was limited to children with elevated body mass index (defined as ≥95th percentile for age and sex). Children with short stature had a higher risk of cardiac- and infection-related death, whereas children with tall stature had a higher risk of cancer-related death.

CONCLUSIONS

Children with short and tall stature are at higher mortality risk, although this association was modified by body mass index at time of first RRT. Studies to further explore the reasons behind the higher risk of mortality in children with extremes of height at the time of first RRT are warranted.

Central blood pressure and chronic kidney disease

In this review, we focused on the relationship between central blood pressure and chronic kidney diseases (CKD). Wave reflection is a major mechanism that determines central blood pressure in patients with CKD. Recent medical technology advances have enabled non-invasive central blood pressure measurements. Clinical trials have demonstrated that compared with brachial blood pressure, central blood pressure is a stronger risk factor for cardiovascular (CV) and renal diseases. CKD is characterized by a diminished renal autoregulatory ability, an augmented direct transmission of systemic blood pressure to glomeruli, and an increase in proteinuria. Any elevation in central blood pressure accelerates CKD progression. In the kidney, interstitial inflammation induces oxidative stress to handle proteinuria. Oxidative stress facilitates atherogenesis, increases arterial stiffness and central blood pressure, and worsens the CV prognosis in patients with CKD. A vicious cycle exists between CKD and central blood pressure. To stop this cycle, vasodilator antihypertensive drugs and statins can reduce central blood pressure and oxidative stress. Even in early-stage CKD, mineral and bone disorders (MBD) may develop. MBD promotes oxidative stress, arteriosclerosis, and elevated central blood pressure in patients with CKD. Early intervention or prevention seems necessary to maintain vascular health in patients with CKD.

Association of Height with Mortality in Patients Undergoing Maintenance Hemodialysis

BACKGROUND AND OBJECTIVES

Body mass index (BMI), determined as kilograms in body weight divided by the square of the height in meters (m(2)), is inversely associated with mortality in patients undergoing maintenance hemodialysis (MHD). It is commonly inferred that differences in the weight component of the BMI equation are responsible for this negative correlation. However, there are almost no data on the relationship between height and mortality in these patients. This study was conducted to examine the association between height and mortality in MHD patients and to evaluate the contribution of height to the BMI-mortality relationship.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A prospective study conducted from July 1, 2001, through June 30, 2006, enrolled a nationally representative cohort of 117,644 MHD patients receiving treatment in DaVita, Inc. outpatient dialysis facilities with (1) known height and weight, (2) age ≥18 years, (3) dialysis vintage ≥90 days, and (4) nonoutlying BMI values (≥12 to ≤60 kg/m(2)). The end date of follow-up was June 30, 2007, and median follow-up was 852 days (interquartile range, 504-1367 days). Mortality hazard ratios were computed within sex-standardized deciles of height and weight, and outcomes included all-cause mortality and cardiovascular, gastrointestinal, cancer, and infection mortality. Hazard models were unadjusted, adjusted for case-mix variables, or adjusted for case-mix variables plus laboratory variables.

RESULTS

Mean age was 61±15 years; 45% of patients were women and 57% had diabetes. In adjusted models, height, also adjusted for weight, was directly associated with all-cause mortality and cardiovascular, infection, and cancer mortality. Compared with the median height decile, mortality risk in the highest height decile was 1.18 (95% confidence interval, 1.14 to 1.23) in fully adjusted analyses (P<0.001). Receiver-operating characteristic curves indicated that in adjusted analyses the contribution of height to the relationship between BMI and mortality was almost identical to that of weight.

CONCLUSIONS

In MHD patients, height is positively associated with mortality risk and contributes similarly to weight with regard to the negative BMI-mortality relationship.

Paradoxical Distribution of Augmentation Index Level in Chronic Kidney Diseases

Pulse wave velocity (PWV) and augmentation index (AI) are used as indexes of arterial stiffness and cardiovascular survival. Although PWV is known to increase as the stage of chronic kidney disease (CKD) advances, how this is related to AI and CKD stage has not yet been well defined.

A sub-analysis was performed using the data from the Antihypertensive and Blood Pressure of Central Artery in Japan study. This was a cross-sectional study on hypertensive patients. All the patients with available serum creatinine levels were selected, and estimated glomerular filtration rate (eGFR) was calculated according to the modification of diet in renal disease equation for a Japanese population. Augmentation indexes at different stages of CKD were compared.

Data from 1392 patients were pooled and analyzed. In addition to eGFR, there were differences in age (P<0.0001), pulse rate (P<0.0001), vasodilator antihypertensive drugs (P<0.005), systolic (P<0.005) and diastolic (P<0.01) blood pressure at 5 CKD stages. Multivariate regression showed that AI correlated to age (0.19%/year), pulse rate (-0.54%/bpm), systolic blood pressure (0.18%/mmHg) and vasodilator antihypertensive drugs (-2.42%/class). Therefore, AI was adjusted for these confounding factors. Adjusted AI in stage 5 (77±20%) was lower than that in stage 1 (84±19%, P<0.05).

These data indicate that AI varies according to CKD stage, and suggest that a cut-off value of AI should be set for each stage of CKD to detect cardiovascular disease.