Racial Differences in Association of Serum Calcium with Mortality and Incident Cardio- and Cerebrovascular Events

CONTEXT

Abnormalities in calcium metabolism may potentially contribute to the development of vascular disease. Calcium metabolism may be different in African American (AA) vs white individuals, but the effect of race on the association of serum calcium with clinical outcomes remains unclear.

OBJECTIVE

This study sought to examine race-specific associations of serum calcium levels with mortality and with major incident cardiovascular events.

DESIGN AND SETTING

This was a historical cohort study in the U.S. Department of Veterans Affairs health care facilities.

PARTICIPANTS

Participants included veterans (n = 1 967 622) with estimated glomerular filtration rate ≥ 60 mL/min/1.73 m².

MAIN OUTCOME MEASURES

The association between serum calcium levels with all-cause mortality, incident coronary heart disease (CHD), and ischemic stroke incidence was examined in multivariable adjusted Cox proportional hazards models, including an interaction term for calcium and race.

RESULTS

The association of calcium with all-cause mortality was U-shaped in both AA and white patients, but race modified the association of calcium with all-cause mortality. Compared with white patients, AA patients experienced lower risk of mortality when calcium was ≥ 8.8 mg/dL, with a statistically significant interaction (P < .001). Conversely, AA vs white race was associated with higher mortality when calcium was < 8.8 mg/dL. Calcium showed no significant association with ischemic stroke or CHD in both races; and race did not modify these associations (P = .37 and 0.11, respectively for interaction term).

CONCLUSIONS

Race modified the U-shaped association between calcium and all-cause mortality. Serum calcium is not associated with incident stroke or CHD in either AA or white patients. The race-specific difference in the association of calcium levels with mortality warrants further examination.

Extended-hours hemodialysis is associated with lower mortality risk in patients with end-stage renal disease

Extended-hours hemodialysis offers substantially longer treatment time compared to conventional hemodialysis schedules and is associated with improved fluid and electrolyte control and favorable cardiac remodeling. However, whether extended-hours hemodialysis improves survival remains unclear. Therefore, we determined the association between extended-hours compared to conventional hemodialysis and the risk of all-cause mortality in a nationally representative cohort of patients initiating maintenance dialysis in the United States from 2007 to 2011. Survival analyses using causal inference modeling with marginal structural models were performed to compare mortality risk among 1206 individuals undergoing thrice weekly extended-hours hemodialysis or 111,707 patients receiving conventional hemodialysis treatments. The average treatment time per session for extended-hours hemodialysis was 399 minutes compared to 211 minutes for conventional therapy. The crude mortality rate with extended-hours hemodialysis was 6.4 deaths per 100 patient-years compared with 14.7 deaths per 100 patient-years for conventional hemodialysis. In the primary analysis, patients treated with extended-hours hemodialysis had a 33% lower adjusted risk of death compared to those who were treated with a conventional regimen (95% confidence interval: 7% to 51%). Additional analyses accounting for analytical assumptions regarding exposure and outcome, facility-level confounders, and prior modality history were similar. Thus, in this large nationally representative cohort, treatment with extended-hours hemodialysis was associated with a lower risk for mortality compared to treatment with conventional in-center therapy. Adequately powered randomized clinical trials comparing extended-hours to conventional hemodialysis are required to confirm these findings.

Constipation and Incident CKD

Constipation is one of the most prevalent conditions in primary care settings and increases the risk of cardiovascular disease, potentially through processes mediated by altered gut microbiota. However, little is known about the association of constipation with CKD. In a nationwide cohort of 3,504,732 United States veterans with an eGFR ≥60 ml/min per 1.73 m², we examined the association of constipation status and severity (absent, mild, or moderate/severe), defined using diagnostic codes and laxative use, with incident CKD, incident ESRD, and change in eGFR in Cox models (for time-to-event analyses) and multinomial logistic regression models (for change in eGFR). Among patients, the mean (SD) age was 60.0 (14.1) years old; 93.2% of patients were men, and 24.7% were diabetic. After multivariable adjustments, compared with patients without constipation, patients with constipation had higher incidence rates of CKD (hazard ratio, 1.13; 95% confidence interval [95% CI], 1.11 to 1.14) and ESRD (hazard ratio, 1.09; 95% CI, 1.01 to 1.18) and faster eGFR decline (multinomial odds ratios for eGFR slope <-10, -10 to <-5, and -5 to <-1 versus -1 to <0 ml/min per 1.73 m² per year, 1.17; 95% CI, 1.14 to 1.20; 1.07; 95% CI, 1.04 to 1.09; and 1.01; 95% CI, 1.00 to 1.03, respectively). More severe constipation associated with an incrementally higher risk for each renal outcome. In conclusion, constipation status and severity associate with higher risk of incident CKD and ESRD and with progressive eGFR decline, independent of known risk factors. Further studies should elucidate the underlying mechanisms.

Volume-related weight gain as an independent indication for renal replacement therapy in the intensive care units

Attempts to identify specific therapies to reverse acute kidney injury (AKI) have been unsuccessful in the past; only modifying risk profile or addressing the underlying disease processes leading to AKI proved efficacious. The current thinking on recognizing AKI is compromised by a "kidney function percent-centered" viewpoint, a paradigm further reinforced by the emergence of serum creatinine-based automated glomerular filtration reporting over the last two decades. Such thinking is, however, grossly corrupted for AKI and poorly applicable in critically ill patients in general. Conventional indications for renal replacement therapy (RRT) may have limited applicability in critically ill patients and there has been a relative lack of progress on RRT modalities in these patients. AKI in critically ill patients is a highly complex syndrome and it may be counterproductive to produce complex clinical practice guidelines, which are labor and resource-intensive to maintain, difficult to memorize or may not be immediately available in all settings all over the world. Additionally, despite attempts to develop reliable and reproducible biomarkers to replace serum creatinine as a guide to therapy such biomarkers failed to materialize. Under such circumstances, there is an ongoing need to reassess the practical value of simple measures, such as volume-related weight gain (VRWG) and urine output, both for prognostic markers and clinical indicators for the need for RRT. This current paper reviews the practical utility of VRWG as an independent indication for RRT in face of reduced urine output and hemodynamic instability.

Increased Risk of Incident Chronic Kidney Disease, Cardiovascular Disease, and Mortality in Patients With Diabetes With Comorbid Depression

OBJECTIVE

It is not known if patients with diabetes with depression have an increased risk of chronic kidney disease (CKD). We examined the association between depression and incident CKD, mortality, and incident cardiovascular events in U.S. veterans with diabetes.

RESEARCH DESIGN AND METHODS

Among a nationally representative prospective cohort of >3 million U.S. veterans with baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2, we identified 933,211 patients with diabetes. Diabetes was ascertained by an ICD-9-CM code for diabetes, an HbA1c >6.4%, or receiving antidiabetes medication during the inclusion period. Depression was defined by an ICD-9-CM code for depression or by antidepressant use during the inclusion period. Incident CKD was defined as two eGFR levels <60 mL/min/1.73 m2 separated by ≥90 days and a >25% decline in baseline eGFR. The associations between depression and outcomes were assessed using Cox proportional regression.

RESULTS

Depression was present in 340,806 patients at enrollment. Depressed patients were younger (61 ± 11 vs. 65 ± 11 years), had higher eGFR (84 ± 15 vs. 81 ± 14 mL/min/1.73 m2), but had more comorbidities. Incident CKD developed in 180,343 patients. Depression was associated with 20% higher risk of incident CKD (adjusted hazard ratio [aHR] and 95% CI: 1.20 [1.19-1.21]). Similarly, depression was associated with increased all-cause mortality (aHR and 95% CI: 1.25 [1.24-1.26]).

CONCLUSIONS

The presence of depression in patients with diabetes is associated with higher risk of developing CKD compared with nondepressed patients. Intervention studies should determine if effective treatment of depression in patients with diabetes would prevent major renal and cardiovascular complications.

Association Between Serum Leptin Level and Mortality in Kidney Transplant Recipients

OBJECTIVE

Leptin is a hormone made by adipocytes and associated with hypertension, inflammation, and coronary artery disease. Low serum leptin level was associated with higher risk of death in patients with advanced chronic kidney disease. Little is known about the association of serum leptin with outcomes in kidney transplant recipients.

DESIGN

Prospective prevalent cohort.

SETTING AND SUBJECT

We collected sociodemographic and clinical parameters, medical and transplant history, and laboratory data of 979 prevalent kidney transplant recipients. Associations between serum leptin level and death with a functioning graft, all-cause death, and death-censored graft loss over a 6-year follow-up period were examined in survival models.

RESULTS

Serum leptin levels showed moderate negative correlation with eGFR (R = -0.21, P < .001) and positive correlations with BMI (R = 0.48, P < .001) and C-reactive protein (R = 0.20, P < .001). Each 10 ng/mL higher serum leptin level was associated with 7% lower risk of death with functioning graft (hazard ratio [HR] (95% confidence interval [CI]), 0.93 (0.87-0.99)), and this association persisted after adjustment for confounders: HR (95% CI), 0.90 (0.82-0.99). Similar associations were found with all-cause death as outcome. The association between serum leptin level and risk of graft loss was nonlinear, and only low serum leptin level was associated with higher risk of graft loss.

CONCLUSIONS

In prevalent kidney transplant recipients, lower serum leptin was an independent predictor of death.

Survival of Elderly Adults Undergoing Incident Home Hemodialysis and Kidney Transplantation

OBJECTIVES

To compare the mortality of elderly adults with end-stage renal disease (ESRD) treated with home hemodialysis (HD) with that of those receiving a kidney transplant (KTx).

DESIGN

Prospective cohort.

SETTING

Pertinent data for the two groups were obtained from electronic medical records from a large dialysis provider and the U.S. Renal Data System.

PARTICIPANTS

Using data from elderly adults (aged ≥65) who started home HD and underwent KTx in the US between 2007 and 2011, a 1:1 propensity score (PS)-matched cohort of 960 elderly adults was created, and the association between treatment modality and all-cause mortality was examined using Cox proportional hazards and competing risk regression survival models using modality failure as a competing event.

MEASUREMENTS

Modality of renal replacement therapy.

RESULTS

The baseline mean age ± standard deviation of the PS-matched individuals undergoing home HD was 71 ± 6, and that of KTx recipients was 71 ± 5, 69% of both groups were male, 81% of those undergoing home HD and 79% of KTx recipients were white, and 11% and 12%, respectively, were African American. Median follow-up time was 205 days (interquartile range (IQR) 78-364 days) for those undergoing home HD and 795 days (IQR 366-1,221 days) for KTx recipients. There were 97 deaths (20%, 253/1,000 patient-years, 95% confidence interval (CI) = 207-309/1,000 patient-years) in the home HD group and 48 deaths (10%, 45/1,000 patient-years, 95% CI = 34-60/1,000 patient-years) in the KTx group. Elderly adults undergoing home HD had a risk of mortality that was almost five times as high as that of KTx recipients (hazard ratio = 4.74, 95% CI = 3.25-6.91). Similar results were seen in competing risk regression analyses (subhazard ratio = 4.71, 95% CI = 3.27-6.79). Results were consistent across different types of kidney donors and subgroups divided according to various recipient characteristics.

CONCLUSION

Elderly adults with ESRD who receive a KTx have greater survival than those who undergo home HD. Further studies are needed to assess whether KTx receipt is associated with other benefits such as better quality of life and lower hospitalization rates.

Neurocognitive functions of pediatric kidney transplant recipients

BACKGROUND

End-stage renal disease (ESRD) in children is associated with impaired neurocognitive function and development. However, data on factors associated with neurocognitive dysfunctions in children with kidney transplants are limited.

METHODS

We conducted a cross-sectional analysis comparing cognitive functions (using the Woodcock-Johnson International Edition, WJIE) in 35 kidney transplant and 35 healthy control children. Data on laboratory measurements, comorbidities, and social characteristics were collected.

RESULTS

Transplant children had significantly worse scores on the intelligence quotient (IQ) test compared with controls [Full Scale IQ score 85 (26) vs 107 (10), p <0.001]. Lower maternal education level was significantly associated with lower WJIE cognitive test scores; however, no association was found between laboratory values and WJIE scores. Among children with kidney transplants, those with medical comorbid conditions had significantly lower Verbal Ability and Full Scale IQ scores. Earlier age of dialysis onset and a longer total time on dialysis (>9 months) were associated with lower test scores. Age-standardized duration of hospitalization was inversely correlated with IQ (r = -0.46, p <0.01) and was an independent significant predictor (Beta = -0.38, p = 0.02) of IQ scores in transplanted children.

CONCLUSIONS

Child kidney transplant recipients have neurocognitive function impairments that are associated with markers of socioeconomic status (SES) and factors related to disease severity.

Concurrence of Serum Creatinine and Albumin With Lower Risk for Death in Twice-Weekly Hemodialysis Patients

OBJECTIVE

Markers of better nutritional status including both higher levels of serum albumin (as a measure of visceral proteins) and creatinine (as a measure of the muscle mass) are associated with lower mortality in conventional (thrice weekly) hemodialysis patients. However, data for these associations in twice-weekly hemodialysis patients, in whom less frequent hemodialysis may confound nutritional predictors, are lacking.

DESIGN AND SUBJECTS

We identified 1,113 twice-weekly and matched 4,448 thrice-weekly hemodialysis patients from a large national dialysis cohort of incident hemodialysis patients over 5 years (2007-2011). Mortality risk, adjusted for potential confounders, was examined across two-by-two combinations of serum creatinine (<6 vs. ≥6 mg/dL) and albumin (<3.5 g/dL vs. ≥3.5 g/dL) for each treatment frequency yielding a total of 8 groups.

RESULTS

Patients were aged 70 ± 14 years and included 48% women and 55% diabetics. Using the thrice-weekly hemodialysis patients with creatinine ≥ 6 mg/dL and albumin ≥ 3.5 g/dL as reference, patients with creatinine <6 mg/dL and albumin <3.5 g/dL had a 1.8-fold higher risk of mortality (hazard ratio: 1.75, 95% confidence interval: 1.33-2.30) in twice-weekly and 2.2-fold increased risk of mortality (hazard ratio: 2.21, 95% confidence interval: 1.81-2.70) in thrice-weekly hemodialysis patients, respectively in fully adjusted models adjusted for demographics, comorbidities, and markers of malnutrition and inflammation. A test for interaction showed that there was no significant difference in albumin creatinine mortality associations between twice-weekly and thrice-weekly hemodialysis patients (P-for-interaction = .7667).

CONCLUSIONS

Surrogate markers of higher visceral protein and muscle mass combined may confer greatest survival in both twice-weekly and thrice-weekly hemodialysis patients.

Age, Race and Cardiovascular Outcomes in African American Veterans

BACKGROUND

In the general population, compared wtih their White peers, African Americans suffer premature all-cause and cardiovascular (CV) deaths, attributed in part to reduced access to care and lower socioeconomic status. Prior reports indicated younger (aged 35 to 44 years) African Americans had a signficantly greater age-adjusted risk of death. Recent studies suggest that in a more egalitarian health care structure than typical United States (US) health care structures, African Americans may have similar or even better CV outcomes, but the impact of age is less well-known.

METHODS

We examined age stratified all-cause mortality, and incident coronary heart disease (CHD) and ischemic stroke in 3,072,966 patients (547,441 African American and 2,525,525 White) with an estimated glomerular filtration rate (eGFR)>60 mL/min/1.73m(2) receiving care from the US Veterans Health Administration. Outcomes were examined in Cox models adjusted for demographics, comorbidities, kidney function, blood pressure, socioeconomics and indicators of the quality of health care delivery.

RESULTS

African Americans had an overall 30% lower all-cause mortality (P<.001) and 29% lower incidence of CHD (P<.001) and higher incidence of ischemic stroke (aHR, 95%CI: 1.16, 1.13-1.18, P<.001). The lower rates of mortality and CHD were strongest in younger African Americans and attenuated across patients aged ≥70 years. Stroke rates did not differ by race in persons aged <70 years.

CONCLUSIONS

Among patients with normal eGFR and receiving care in the Veterans Health Administration, younger African Americans had lower all-cause mortality and incidence of CHD and similar rates of stroke, independent of demographic, comorbidity and socioeconomic differences. The lower all-cause mortality persisted but attenuated with increasing age and the lower incidence of CHD ended at aged ≥80 years. The higher incidence of ischemic stroke in African Americans was driven by increasing risk in patients aged ≥70 years suggesting that the improved cardiovascular outcomes were most dramatic for younger African Americans.

Comparisons of sleep apnoea rate and outcomes among patients with resistant and non-resistant hypertension

BACKGROUND AND OBJECTIVE

We directly compared sleep apnoea (SA) rates and risk of cardiovascular and mortality outcomes among SA patients with resistant hypertension (RH) and non-RH within a large diverse hypertension population.

METHODS

A retrospective cohort study between 1 January 2006 and 31 December 2010 among hypertensive adults (age ≥ 18 years) was performed within an integrated health system. Rates of SA in RH and non-RH were determined. Multivariable logistic regression analyses were used to calculate OR for SA. Cox proportional hazard modelling was used to estimate hazard ratios (HRs) for cardiovascular and mortality outcomes between SA in RH versus SA in non-RH adjusting for age, gender, race, BMI, chronic kidney disease and other comorbidities.

RESULTS

SA was identified in 33 682 (7.2%) from 470 386 hypertensive individuals. SA in RH accounted for 5806 (9.6%) compared to SA in non-RH 27 876 individuals (6.8%). Multivariable OR (95% CI) for SA was 1.16 (1.12, 1.19), 3.57 (3.47, 3.66) and 2.20 (2.15, 2.25) for RH versus non-RH, BMI ≥ 30, and males, respectively. Compared to SA in non-RH individuals, SA in RH had a multivariable adjusted HR (95% CI) of 1.24 (1.13, 1.36), 1.43 (1.28, 1.61), 0.98 (0.85, 1.12) and 1.04 (0.95, 1.14) for ischaemic heart event (IHE), congestive heart failure (CHF), stroke and mortality, respectively.

CONCLUSION

We observed a modest increase in likelihood for SA among RH compared to non-RH patients. Risks for IHE and CHF were higher for SA in RH compared to SA in non-RH patients; however, there were no differences in risk for stroke and mortality.

Mean platelet volume and mortality risk in a national incident hemodialysis cohort

BACKGROUND

Higher mean platelet volume (MPV) is an indicator of larger, reactive platelets, and has been associated with a higher risk of thrombosis and cardiovascular events in the general population. Hemodialysis patients have a higher risk for cardiovascular death and predisposition to platelet dysfunction (thrombosis and bleeding diathesis), but the relationship between MPV and mortality in this population is unknown.

METHODS

Among a 5-year cohort (1/2007-12/2011) of 149,118 incident hemodialysis patients from a large national dialysis organization, we examined the association between MPV and all-cause mortality. In primary analyses, we granularly analyzed MPV across five categories: 7.2-7.5, >7.5-9.5, >9.5-11.5, >11.5-13.5, and >13.5-15.0fL. In secondary analyses, we examined MPV categorized as low, normal, and high based on thresholds in the general population: 7.2-7.5, >7.5-11.5, and >11.5fL, respectively. Associations between baseline and time-dependent MPV with mortality were estimated using traditional and time-dependent Cox models in order to determine long-term and short-term exposure-mortality associations, respectively, using three adjustment levels: unadjusted, case-mix, and case-mix+laboratory models.

RESULTS

In primary analyses, higher baseline and time-dependent MPV levels were associated with incrementally higher death risk in case-mix+laboratory analyses (reference: >9.5-11.5fL). In secondary analyses, high baseline and time-dependent MPV levels were associated with higher mortality, whereas low MPV was associated with lower death risk across all multivariable models (reference: normal MPV).

CONCLUSIONS

Hemodialysis patients with higher MPV have heightened mortality risk. Further studies are needed to determine the pathophysiologic basis for the higher risk, and if modification of MPV ameliorates mortality in this population.

Age and Outcomes Associated with BP in Patients with Incident CKD

BACKGROUND AND OBJECTIVES

Hypertension is the most important treatable risk factor for cardiovascular outcomes. Many patients with CKD are elderly, but the ideal BP in these individuals is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

From among 339,887 patients with incident eGFR<60 ml/min per 1.73 m(2), we examined associations of systolic BP (SBP) and diastolic BP (DBP) with all-cause mortality, incident coronary heart disease (CHD), ischemic strokes, and ESRD from the time of developing CKD until the end of follow-up (July 26, 2013, for mortality, CHD, and stroke, and December 31, 2011, for ESRD) in multivariable-adjusted survival models categorized by patients' age.

RESULTS

Of the total cohort, 300,424 (88%) had complete data for multivariable analysis. Both SBP and DBP showed a U-shaped association with mortality. SBP displayed a linear association with CHD, stroke, and ESRD, whereas DBP showed no consistent association with either. SBP>140 mmHg was associated with higher incidence of all examined outcomes, but with an incremental attenuation of the observed risk in older compared with younger patients (P<0.05 for interaction) The adjusted hazard ratios and 95% confidence intervals associated with SBP≥170 mmHg (compared with 130-139 mmHg) in patients <50, 50-59, 60-69, 70-79, and ≥80 years were 1.95 (1.34 to 2.84), 2.01 (1.75 to 2.30), 1.68 (1.49 to 1.89), 1.39 (1.25 to 1.54), and 1.30 (1.17 to 1.44), respectively. The risk of incident CHD, stroke, and ESRD was incrementally higher with higher SBP in patients aged <80 years but showed no consistent association in those aged ≥80 years (P<0.05 for interaction for all outcomes).

CONCLUSIONS

In veterans with incident CKD, SBP showed different associations in older versus younger patients. The association of higher SBP with adverse outcomes was present but markedly reduced in older individuals, especially in those aged ≥80 years. Elevated DBP showed no consistent association with vascular outcomes in patients with incident CKD.

Synergistic association of combined glycemic and blood pressure level with risk of complications in US veterans with diabetes

OBJECTIVES

Hemoglobin A1c levels less than 7.0% and systolic blood pressure (SBP) less than 140 mmHg are each associated with lower risk of vascular complications in patients with diabetes mellitus. Associations between combined A1c level and SBP categories and risk of mortality and morbidity in diabetic patients are not well characterized.

METHODS

We examined 891 670 US diabetic veterans with baseline estimated glomerular filtration rates more than 60 ml/min per 1.73 m (mean age 67 ± 11 years, 97% men, 17% African-Americans). The associations of mutually exclusive combined categories of A1c (<6.5, 6.5-6.9, 7.0-7.9, 8.0-8.9, 9.0-9.9, and ≥10%) and SBP (<100, 100-119, 120-139, 140-159, 160-179, and ≥180 mmHg) with the risk of all-cause mortality and incident chronic kidney disease (CKD), coronary heart disease, and stroke were examined in Cox models adjusted for baseline characteristics using patients with concomitant A1c 6.5-6.9% and SBP of 120-139 mmHg as the referent group.

RESULTS

A total of 221 529 (25%) patients died, and 178 588 (20%), 43 373 (5%) and 36 935 (4%) developed CKD, coronary heart disease and stroke, respectively, during a median follow-up of 7.4 years. SBP displayed a J-shaped association with each outcome except CKD risk that was linearly associated with SBP across all A1c categories. A1c above 7.0% was associated with monotonically worse outcomes for all end points in all SBP categories. Patients with the combined highest A1c and SBP levels experienced the worst outcomes.

CONCLUSION

SBP greater than 120-139 mmHg and A1c greater than 7.0% are associated with higher mortality and vascular complications in diabetic patients, independent of each other. Combined efforts to improve both glycemic and blood pressure control may synergistically improve outcomes in patients with normal kidney function.

Predialysis Cardiovascular Disease Medication Adherence and Mortality After Transition to Dialysis

BACKGROUND

Medication nonadherence is a known risk factor for adverse outcomes in the general population. However, little is known about the association of predialysis medication adherence among patients with advanced chronic kidney disease and mortality following their transition to dialysis.

STUDY DESIGN

Observational study.

SETTING & PARTICIPANTS

32,348 US veterans who transitioned to dialysis during 2007 to 2011.

PREDICTORS

Adherence to treatment with cardiovascular drugs, ascertained from pharmacy database records using proportion of days covered (PDC) and persistence during the predialysis year.

OUTCOMES

Post-dialysis therapy initiation all-cause and cardiovascular mortality, using Cox models with adjustment for confounders.

RESULTS

Mean age of the cohort was 72±11 (SD) years; 96% were men, 74% were white, 23% were African American, and 69% had diabetes. During a median follow-up of 23 (IQR, 9-36) months, 18,608 patients died. Among patients with PDC>80%, there were 14,006 deaths (mortality rate, 283 [95% CI, 278-288]/1,000 patient-years]); among patients with PDC>60% to 80%, there were 3,882 deaths (mortality rate, 294 [95% CI, 285-304]/1,000 patient-years); among patients with PDC≤60%, there were 720 deaths (mortality rate, 291 [95% CI, 271-313]/1,000 patient-years). Compared with patients with PDC>80%, the adjusted HR for post-dialysis therapy initiation all-cause mortality for patients with PDC>60% to 80% was 1.12 (95% CI, 1.08-1.16), and for patients with PDC≤60% was 1.21 (95% CI, 1.11-1.30). In addition, compared with patients showing medication persistence, adjusted HR risk for post-dialysis therapy initiation all-cause mortality for patients with nonpersistence was 1.11 (95% CI, 1.05-1.16). A similar trend was detected for cardiovascular mortality and in subgroup analyses.

LIMITATIONS

Large number of missing values; results may not be generalizable to women or the general US population.

CONCLUSIONS

Predialysis cardiovascular medication nonadherence is an independent risk factor for postdialysis mortality in patients with advanced chronic kidney disease transitioning to dialysis therapy. Further studies are needed to assess whether interventions targeting adherence improve survival after dialysis therapy initiation.

Adipocytokines in renal transplant recipients

In the last two decades, perceptions about the role of body fat have changed. Adipocytes modulate endocrine and immune homeostasis by synthesizing hundreds of hormones, known as adipocytokines. Many studies have been investigating the influences and effects of these adipocytokines and suggest that they are modulated by the nutritional and immunologic milieu. Kidney transplant recipients (KTRs) are a unique and relevant population in which the function of adipocytokines can be examined, given their altered nutritional and immune status and subsequent dysregulation of adipocytokine metabolism. In this review, we summarize the recent findings about four specific adipocytokines and their respective roles in KTRs. We decided to evaluate the most widely described adipocytokines, including leptin, adiponectin, visfatin and resistin. Increasing evidence suggests that these adipocytokines may lead to cardiovascular events and metabolic changes in the general population and may also increase mortality and graft loss rate in KTRs. In addition, we present findings on the interrelationship between serum adipocytokine levels and nutritional and immunologic status, and mechanisms by which adipocytokines modulate morbidity and outcomes in KTRs.

Candidate Surrogate End Points for ESRD after AKI

AKI, a frequently transient condition, is not accepted by the US Food and Drug Association as an end point for drug registration trials. We assessed whether an intermediate-term change in eGFR after AKI has a sufficiently strong relationship with subsequent ESRD to serve as an alternative end point in trials of AKI prevention and/or treatment. Among 161,185 United States veterans undergoing major surgery between 2004 and 2011, we characterized in-hospital AKI by Kidney Disease Improving Global Outcomes creatinine criteria and decline in eGFR from prehospitalization to postdischarge time points and quantified associations of these values with ESRD and mortality over a median of 3.8 years. An eGFR decline of ≥30% at 30, 60, and 90 days after discharge occurred in 3.1%, 2.5%, and 2.6%, of survivors without AKI and 15.9%, 12.2%, and 11.7%, of survivors with AKI. For patients with in-hospital AKI compared with those with no AKI and stable eGFR, a 30% decline in eGFR at 30, 60, and 90 days after discharge demonstrated adjusted hazard ratios (95% confidence intervals) of ESRD of 5.60 (4.06 to 7.71), 6.42 (4.76 to 8.65), and 7.27 (5.14 to 10.27), with corresponding estimates for 40% decline in eGFR of 6.98 (5.21 to 9.35), 8.03 (6.11 to 10.56), and 10.95 (8.10 to 14.82). Risks for mortality were smaller but consistent in direction. A 30%-40% decline in eGFR after AKI could be a surrogate end point for ESRD in trials of AKI prevention and/or treatment, but additional trial evidence is needed.

Association of incident restless legs syndrome with outcomes in a large cohort of US veterans

Restless legs syndrome is a common sleep disorder, but there is a paucity of large cohort studies examining the association of restless legs syndrome with clinical outcomes, including all-cause mortality, incident coronary heart disease, stroke and chronic kidney disease. From a nationally representative prospective cohort of over 3 million US veterans [93% male, median follow-up time of 8.1 years (interquartile range: 7.0-8.5 years)] with baseline estimated glomerular filtration rate ≥ 60 mL min(-1) 1.73 m(-2), a propensity-matched cohort of 7392 patients was created, and the association between incident restless legs syndrome and the following was examined: (1) all-cause mortality; (2) incident coronary heart disease; (3) incident strokes; and (4) incident chronic kidney disease defined as estimated glomerular filtration rate <60 mL min(-1) 1.73 m(-2). Associations were examined using Cox models. The mean ± SD age of the propensity-matched cohort at baseline was 59 ± 12 years; 89 and 8% of patients were white and black, respectively; 31% of the patients were diabetic; and the mean baseline estimated glomerular filtration rate was 83.9 ± 15.1 mL min(-1) 1.73 m(-2). Propensity matching resulted in a balanced cohort, with the disappearance in baseline differences in comorbidities. Compared with restless legs syndrome-negative patients, incident restless legs syndrome was associated with 88% higher mortality risk [hazard ratio and 95% confidence interval: 1.88 (1.70-2.08)], and almost four times higher risk of coronary heart disease and stroke [hazard ratio: 3.97 (3.26-4.84) and 3.89 (3.07-4.94), respectively]. The risk of incident chronic kidney disease was also significantly higher in incident restless legs syndrome patients [hazard ratio: 3.17 (2.74-3.66)] compared with restless legs syndrome-negative counterparts. In this large and contemporary cohort of US veterans, incident restless legs syndrome was associated with higher risk of mortality, incident coronary heart disease, stroke and chronic kidney disease.

Association of Slopes of Estimated Glomerular Filtration Rate With Post-End-Stage Renal Disease Mortality in Patients With Advanced Chronic Kidney Disease Transitioning to Dialysis

OBJECTIVE

To investigate the association of estimated glomerular filtration rate (eGFR) slopes before dialysis initiation with cause-specific mortality after dialysis initiation.

PATIENTS AND METHODS

In this retrospective cohort study of 18,874 US veterans who had transitioned to dialysis from October 1, 2007, through September 30, 2011, we examined the association of pre-end-stage renal disease (ESRD) eGFR slopes with all-cause, cardiovascular, and infection-related mortality during the post-ESRD period over a median follow-up of 2.0 years (interquartile range, 1.1-3.2 years). Associations were examined using Cox models with adjustment for potential confounders.

RESULTS

Before the 18,874 patients transitioned to dialysis, 4485 (23.8%), 5633 (29.8%), and 7942 (42.1%) experienced fast, moderate, and slow eGFR decline, respectively, and 814 (4.3%) had increasing eGFR (defined as eGFR slopes of less than -10, -10 to less than -5, -5 to <0, and ≥0 mL/min per 1.73 m(2) per year). During the study period, a total of 9744 all-cause, 2702 cardiovascular, and 604 infection-related deaths were observed. Compared with patients with slow eGFR decline, those with moderate and fast eGFR decline had a higher risk of all-cause mortality (adjusted hazard ratio [HR], 1.06; 95% CI, 1.00-1.11; and HR, 1.11; 95% CI, 1.04-1.18, respectively) and cardiovascular mortality (HR, 1.11; 95% CI, 1.01-1.23 and HR, 1.13; 95% CI, 1.00-1.27, respectively). In contrast, increasing eGFR was only associated with higher infection-related mortality (HR, 1.49; 95% CI, 1.03-2.17).

CONCLUSION

Rapid eGFR decline is associated with higher all-cause and cardiovascular mortality, and increasing eGFR is associated with higher infection-related mortality among incident dialysis cases.

Red Cell Distribution Width and Mortality in Hemodialysis Patients

BACKGROUND

Red cell distribution width (RDW) is an index of red blood cell volume variability that has historically been used as a marker of iron deficiency anemia. More recently, studies have shown that elevated RDW is associated with higher mortality risk in the general population. However, there is lack of data demonstrating the association between RDW and mortality risk in hemodialysis (HD) patients. We hypothesized that higher RDW is associated with higher mortality in HD patients.

STUDY DESIGN

Retrospective observational study using a large HD patient cohort.

SETTING & PARTICIPANTS

109,675 adult maintenance HD patients treated in a large dialysis organization from January 1, 2007, to December 31, 2011.

PREDICTOR

Baseline and time-varying RDW, grouped into 5 categories: <14.5%, 14.5% to <15.5%, 15.5% to <16.5%, 16.5% to <17.5%, and ≥17.5%. RDW of 15.5% to <16.5% was used as the reference category.

OUTCOME

All-cause mortality.

RESULTS

Mean age of study participants was 63±15 (SD) years and the study cohort was 44% women. In baseline and time-varying analyses, there was a graded association between higher RDW and incrementally higher mortality risk. Receiver operating characteristic, net reclassification analysis, and integrated discrimination improvement analyses demonstrated that RDW is a stronger predictor of mortality as compared with traditional markers of anemia, such as hemoglobin, ferritin, and iron saturation values.

LIMITATIONS

Lack of comprehensive data that may be associated with both RDW and HD patient outcomes, such as blood transfusion data, socioeconomic status, and other unknown confounders; therefore, the possibility of residual confounding could not be excluded. Also, lack of information for cause of death; thus, cardiovascular mortality outcomes could not be examined.

CONCLUSIONS

In HD patients, higher RDW is associated with incrementally higher mortality risk. RDW is also a stronger predictor of mortality than traditional laboratory markers of anemia. Further studies are needed to determine the mechanisms underlying the association between RDW and mortality.

Association between serum resistin level and outcomes in kidney transplant recipients

Resistin is an adipocytokine that is associated with inflammation, coronary artery disease, and other types of cardiovascular disease among patients with normal kidney function. However, little is known about the association of resistin with outcomes in kidney transplant recipients. We collected socio-demographic and clinical parameters, medical and transplant history, and laboratory data from 988 prevalent kidney transplant recipients enrolled in the Malnutrition-Inflammation in Transplant-Hungary Study (MINIT-HU study). Serum resistin levels were measured at baseline. Associations between serum resistin level and death with a functioning graft over a 6-year follow-up period were examined in unadjusted and adjusted models. The mean±SD age of the study population was 51 ± 13 years, among whom 57% were men and 21% were diabetics. Median serum resistin concentrations were significantly higher in patients who died with a functioning graft as compared to those who did not die during the follow-up period (median [IQR]: 22[15-26] vs. 19[14-22] ng/ml, respectively; P < 0.001). Higher serum resistin level was associated with higher mortality risk in both unadjusted and fully adjusted models: HRs (95% CI): 1.33(1.16-1.54) and 1.21(1.01-1.46), respectively. In prevalent kidney transplant recipients, serum resistin was an independent predictor of death with a functioning graft.

Association of Vascular Access Type with Mortality, Hospitalization, and Transfer to In-Center Hemodialysis in Patients Undergoing Home Hemodialysis

BACKGROUND AND OBJECTIVES

In individuals undergoing in-center hemodialysis (HD), use of central venous catheters (CVCs) is associated with worse clinical outcomes compared with use of arteriovenous access. However, it is unclear whether a similar difference in risk by vascular access type is present in patients undergoing home HD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our study examined the associations of vascular access type with all-cause mortality, hospitalization, and transfer to in-center HD in patients who initiated home HD from 2007 to 2011 in 464 facilities in 43 states in the United States. Patients were followed through December 31, 2011. Data were analyzed using competing risks hazards regression, with vascular access type at the start of home HD as the primary exposure in a propensity score-matched cohort (1052 patients; 526 with CVC and 526 with arteriovenous access).

RESULTS

Over a median follow-up of 312 days, 110 patients died, 604 had at least one hospitalization, and 202 transferred to in-center hemodialysis. Compared with arteriovenous access use, CVC use was associated with higher risk for mortality (hazard ratio, 1.73; 95% confidence interval, 1.18 to 2.54) and hospitalization (hazard ratio, 1.19; 95% confidence interval, 1.02 to 1.39). CVC use was not associated with increased risk for transfer to in-center HD. The results of analyses in the entire unmatched cohort (2481 patients), with vascular access type modeled as a baseline exposure at start of home HD or a time-varying exposure, were similar. Analyses among a propensity score-matched cohort of patients undergoing in-center HD also showed similar risks for death and hospitalization with use of CVCs.

CONCLUSIONS

In a large cohort of patients on home HD, CVC use was associated with higher risk for mortality and hospitalization. Additional studies are needed to identify interventions which may reduce risk associated with use of CVCs among patients undergoing home HD.

Racial and Ethnic Disparities in Use of and Outcomes with Home Dialysis in the United States

Home dialysis, which comprises peritoneal dialysis (PD) or home hemodialysis (home HD), offers patients with ESRD greater flexibility and independence. Although ESRD disproportionately affects racial/ethnic minorities, data on disparities in use and outcomes with home dialysis are sparse. We analyzed data of patients who initiated maintenance dialysis between 2007 and 2011 and were admitted to any of 2217 dialysis facilities in 43 states operated by a single large dialysis organization, with follow-up through December 31, 2011 (n =: 162,050, of which 17,791 underwent PD and 2536 underwent home HD for ≥91 days). Every racial/ethnic minority group was significantly less likely to be treated with home dialysis than whites. Among individuals treated with in-center HD or PD, racial/ethnic minorities had a lower risk for death than whites; among individuals undergoing home HD, only blacks had a significantly lower death risk than whites. Blacks undergoing PD or home HD had a higher risk for transfer to in-center HD than their white counterparts, whereas Asians or others undergoing PD had a lower risk than whites undergoing PD. Blacks irrespective of dialysis modality, Hispanics undergoing PD or in-center HD, and Asians and other racial groups undergoing in-center HD were significantly less likely than white counterparts to receive a kidney transplant. In conclusion, there are racial/ethnic disparities in use of and outcomes with home dialysis in the United States. Disparities in kidney transplantation evident for blacks and Hispanics undergoing home dialysis are similar to those with in-center HD. Future studies should identify modifiable causes for these disparities.

Association of Pre-Operative Albuminuria with Post-Operative Outcomes after Coronary Artery Bypass Grafting

The effect on post-operative outcomes after coronary artery bypass graft(CABG) surgery is not clear. Among 17,812 patients who underwent CABG during October 1,2006-September 28,2012 in any Department of US Veterans Affairs(VA) hospital, we identified 5,968 with available preoperative urine albumin-creatinine ratio(UACR) measurements. We examined the association of UACR<30, 30–299 and >=300 mg/g with 30/90/180/365-day and overall all-cause mortality, and hospitalization length >10 days, and with acute kidney injury(AKI). Mean ± SD baseline age and eGFR were 66 ± 8 years and 77 ± 19 ml/min/1.73 m², respectively. 788 patients(13.2%) died during a median follow-up of 3.2 years, and 26.8% patients developed AKI(23.1%-Stage 1; 2.9%-Stage 2; 0.8%-Stage 3) within 30 days of CABG. The median lengths of stay were 8 days(IQR: 6–13 days), 10 days(IQR: 7–14 days) and 12 days(IQR: 8–19 days) for groups with UACR < 30 mg/g, 30–299 mg/g and ≥300 mg/g, respectively. Higher UACR conferred 72 to 85% higher 90-, 180-, and 365-day mortality compared to UACR<30 mg/g (odds ratio and 95% confidence interval for UACR≥300 vs. <30 mg/g: 1.72(1.01–2.95); 1.85(1.14–3.01); 1.74(1.15–2.61), respectively). Higher UACR was also associated with significantly longer hospitalizations and higher incidence of all stages of AKI. Higher UACR is associated with significantly higher odds of mortality, longer post-CABG hospitalization, and higher AKI incidence.

Association of Race With Mortality and Cardiovascular Events in a Large Cohort of US Veterans

BACKGROUND

In the general population, blacks experience higher mortality than their white peers, attributed in part to their lower socioeconomic status, reduced access to care, and possibly intrinsic biological factors. Patients with kidney disease are a notable exception, among whom blacks experience lower mortality. It is unclear if similar differences affecting outcomes exist in patients with no kidney disease but with equal or similar access to health care.

METHODS AND RESULTS

We compared all-cause mortality, incident coronary heart disease, and incident ischemic stroke using multivariable-adjusted Cox models in a nationwide cohort of 547 441 black and 2 525 525 white patients with baseline estimated glomerular filtration rate ≥ 60 mL·min⁻¹·1.73 m⁻² receiving care from the US Veterans Health Administration. In parallel analyses, we compared outcomes in black versus white individuals in the National Health and Nutrition Examination Survey (NHANES) 1999 to 2004. After multivariable adjustments in veterans, black race was associated with 24% lower all-cause mortality (adjusted hazard ratio, 0.76; 95% confidence interval, 0.75-0.77; P<0.001) and 37% lower incidence of coronary heart disease (adjusted hazard ratio, 0.63; 95% confidence interval, 0.62-0.65; P<0.001) but a similar incidence of ischemic stroke (adjusted hazard ratio, 0.99; 95% confidence interval, 0.97-1.01; P=0.3). Black race was associated with a 42% higher adjusted mortality among individuals with estimated glomerular filtration rate ≥ 60 mL·min⁻¹·1.73 m⁻² in NHANES (adjusted hazard ratio, 1.42; 95% confidence interval, 1.09-1.87).

CONCLUSIONS

Black veterans with normal estimated glomerular filtration rate and equal access to healthcare have lower all-cause mortality and incidence of coronary heart disease and a similar incidence of ischemic stroke. These associations are in contrast to the higher mortality experienced by black individuals in the general US population.

Peritoneal Equilibration Test and Patient Outcomes

BACKGROUND AND OBJECTIVES

Although a peritoneal equilibration test yields data on three parameters (4-hour dialysate/plasma creatinine, 4- to 0-hour dialysate glucose, and 4-hour ultrafiltration volume), all studies have focused on the prognostic value of dialysate/plasma creatinine for patients undergoing peritoneal dialysis. Because dialysate 4- to 0-hour glucose and ultrafiltration volume may be superior in predicting daily ultrafiltration, the likely mechanism for the association of peritoneal equilibration test results with outcomes, we hypothesized that they are superior to dialysate/plasma creatinine for risk prediction.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined unadjusted and adjusted associations of three peritoneal equilibration test parameters with all-cause mortality, technique failure, and hospitalization rate in 10,142 patients on peritoneal dialysis treated between January 1, 2007 and December 31, 2011 in 764 dialysis facilities operated by a single large dialysis organization in the United States, with a median follow-up period of 15.8 months; 87% were treated with automated peritoneal dialysis.

RESULTS

Demographic and clinical parameters explained only 8% of the variability in dialysate/plasma creatinine. There was a linear association between dialysate/plasma creatinine and mortality (adjusted hazards ratio per 0.1 unit higher, 1.07; 95% confidence interval, 1.02 to 1.13) and hospitalization rate (adjusted incidence rate ratio per 0.1 unit higher, 1.05; 95% confidence interval, 1.03 to 1.06). Dialysate/plasma creatinine and dialysate glucose were highly correlated (r=-0.84) and yielded similar risk prediction. Ultrafiltration volume was inversely related with hospitalization rate but not with all-cause mortality. None of the parameters were associated with technique failure. Adding 4- to 0-hour dialysate glucose, ultrafiltration volume, or both did not result in any improvement in risk prediction with dialysate/plasma creatinine alone.

CONCLUSIONS

This analysis from a large contemporary cohort treated primarily with automated peritoneal dialysis validates dialysate/plasma creatinine as a robust predictor of outcomes in patients treated with peritoneal dialysis.

Impact of Non-Adherence on Renal and Cardiovascular Outcomes in US Veterans

BACKGROUND

Adherence is paramount in treating hypertension; however, no gold standard method is available for non-adherence screening, delineating high-risk patients. An International Classification of Diseases 9th Edition non-adherence diagnostic code (V15.81) has been available for decades; but, its utility is poorly studied. We examined the association between the V15.81 code assigned prior to the initiation of anti-hypertensive drugs (AHDs) and renal and cardiovascular outcomes.

METHODS

This was a historical prospective cohort study involving 312,489 newly treated hypertensive individuals (mean age 53.8 years, 90.9% males, 20.3% black, median follow-up 8.0 years). We used crude and Cox models adjusted for baseline socio-demographic characteristics, estimated glomerular filtration rate (eGFR), body mass index, blood pressure, comorbidities, and prospective AHD adherence (measured as proportion of days covered, PDC).

RESULTS

In the unadjusted analysis, the V15.81 code was associated with higher risks for faster eGFR decline (hazard ratio, HR 1.22, 95% CI 1.11-1.33), incident CKD (HR 1.17, 95% CI 1.09-1.27), end-stage renal disease (ESRD) (HR 2.53, 95% CI 1.72-3.72), incident coronary artery disease (CAD) (HR 1.26, 95% CI 1.15-1.38), and stroke (HR 1.55, 95% CI 1.38-1.73). In the adjusted model, the V15.81 code remained predictive of increased risk of CKD (HR 1.33, 95% CI 1.22-1.45), ESRD (HR 1.81, 95% CI 1.18-2.78), incident CAD (HR 1.26, 95% CI 1.14-1.40), and stroke (HR 1.46, 95% CI 1.29-1.65). Additional adjustment for PDC did not alter adverse associations between V15.81 code and studied outcomes.

CONCLUSIONS

Assignment of V15.81 code prior to AHD therapy was associated with higher risks of renal and cardiovascular outcomes in incident hypertensive US veterans. Previous history of non-adherence is a poor prognostic marker in hypertensive individuals; therefore, patients with V15.81 code may require close monitoring. The observational nature of this study limits our ability to make firm recommendations for clinical practice.

Reverse Epidemiology of Traditional Cardiovascular Risk Factors in the Geriatric Population

Traditional risk factors of cardiovascular death in the general population, including body mass index (BMI), serum cholesterol, and blood pressure (BP), are also found to relate to outcomes in the geriatric population, but in an opposite direction. Some degrees of elevated BMI, serum cholesterols, and BP are reportedly associated with lower, instead of higher, risk of death among the elderly. This phenomenon is termed "reverse epidemiology" or "risk factor paradox" (such as obesity paradox) and is also observed in a variety of chronic disease states such as end-stage renal disease requiring dialysis, chronic heart failure, rheumatoid arthritis, and AIDS. Several possible causes are hypothesized to explain this risk factor reversal: competing short-term and long-term killers, improved hemodynamic stability in the obese, adipokine protection against tumor necrosis factor-α, lipoprotein protection against endotoxins, and lipophilic toxin sequestration by the adipose tissue. It is possible that the current thresholds for intervention and goal levels for such traditional risk factors as BMI, serum cholesterol, and BP derived based on younger populations do not apply to the elderly, and that new levels for such risk factors should be developed for the elderly population. Reverse epidemiology of conventional cardiovascular risk factors may have a bearing on the management of the geriatric population, thus it deserves further attention.

Acute Kidney Injury After Major Surgery: A Retrospective Analysis of Veterans Health Administration Data

BACKGROUND

Few trials of acute kidney injury (AKI) prevention after surgery have been conducted, and most observational studies focus on AKI following cardiac surgery. The frequency of, risk factors for, and outcomes after AKI following other types of major surgery have not been well characterized and may present additional opportunities for trials in AKI.

STUDY DESIGN

Observational cohort study.

SETTING & PARTICIPANTS

3.6 million US veterans followed up from 2004 to 2011 for the receipt of major surgery (cardiac; general; ear, nose, and throat; thoracic; vascular; urologic; and orthopedic) and postoperative outcomes.

FACTORS

Demographics, health characteristics, and type of surgery.

OUTCOMES

Postoperative AKI defined by the KDIGO creatinine criteria, postoperative length of stay, end-stage renal disease, and mortality.

RESULTS

Postoperative AKI occurred in 11.8% of the 161,185 major surgery hospitalizations (stage 1, 76%; stage 2, 15%, stage 3 [without dialysis], 7%; and AKI requiring dialysis, 2%). Cardiac surgery had the highest postoperative AKI risk (relative risk [RR], 1.22; 95% CI, 1.17-1.27), followed by general (reference), thoracic (RR, 0.92; 95% CI, 0.87-0.98), orthopedic (RR, 0.70; 95% CI, 0.67-0.73), vascular (RR, 0.68; 95% CI, 0.64-0.71), urologic (RR, 0.65; 95% CI, 0.61-0.69), and ear, nose, and throat (RR, 0.32; 95% CI, 0.28-0.37) surgery. Risk factors for postoperative AKI included older age, African American race, hypertension, diabetes mellitus, and, for estimated glomerular filtration rate < 90mL/min/1.73m(2), lower estimated glomerular filtration rate. Participants with postoperative AKI had longer lengths of stay (15.8 vs 8.6 days) and higher rates of 30-day hospital readmission (21% vs 13%), 1-year end-stage renal disease (0.94% vs 0.05%), and mortality (19% vs 8%), with similar associations by type of surgery and more severe stage of AKI relating to poorer outcomes.

LIMITATIONS

Urine output was not available to classify AKI; cohort included mostly men.

CONCLUSIONS

AKI was common after major surgery, with similar risk factor and outcome associations across surgery type. These results can inform the design of clinical trials in postoperative AKI to the noncardiac surgery setting.

Association of age and BMI with kidney function and mortality: a cohort study

BACKGROUND

Compared with normal weight, obesity might be associated with worse clinical outcomes, including chronic kidney disease. Whether this association is modified by age is not known. We investigated the association of BMI with progressive loss of kidney function and all-cause mortality in US veterans.

METHODS

In a national cohort of 3,376,187 US veterans with an estimated glomerular filtration rate (eGFR) of more than 60 mL/min per 1·73 m(2), we assessed the association of BMI in patients of different ages (<40 years, 40 years to <50 years, 50 years to <60 years, 60 years to <70 years, 70 years to <80 years, and ≥80 years) with loss of kidney function and with all-cause mortality in logistic regression models and Cox proportional hazards models adjusted for ethnic origin, sex, comorbidities, medications, and baseline eGFR.

FINDINGS

274,764 (8·1%) of 3,376,187 veterans had a rapid decline in kidney function (decrease in slope of >5 mL/min per 1·73 m(2)). The lowest risk for loss of kidney function was noted in patients with BMI of at least 25 kg/m(2) but less than 30 kg/m(2). A generally consistent U-shaped association was noted between BMI and rapid loss of kidney function that was more prominent with increasing age, except in the patients younger than 40 years, in whom BMI did not seem to be predictive of renal function impairment. 672,341 veterans died (28·7 per 1000 patient-years, 95% CI 28·6-28·7) over a median follow-up of 6·8 years (IQR 6·5-7·7). BMI also showed a U-shaped association with mortality, which was similar in all age groups.

INTERPRETATION

A BMI of 30 kg/m(2) or more is associated with rapid loss of kidney function in patients with eGFR of at least 60 mL/min per 1·73 m(2), and this association is accentuated in older patients. A BMI of 35 kg/m(2) or more is also associated with high mortality. A BMI of at least 25 kg/m(2) but less than 30 kg/m(2) is associated with the best clinical outcomes.

FUNDING

National Institute of Health, Memphis VA Medical Center, Long Beach VA Healthcare System, Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Health Services Research and Development, and VA Information Resource Center.

Association of aspartate aminotransferase with mortality in hemodialysis patients

BACKGROUND

Liver disease is a common comorbid condition in maintenance hemodialysis (MHD) patients and may be associated with poor survival. The relationship between aspartate aminotransferase (AST) and survival has not yet been addressed in these patients. We hypothesized that higher AST level is associated with higher death risk in MHD patients.

METHODS

A 5-year (January 2007-December 2011) cohort of 109 718 MHD patients was studied in the USA in dialysis clinics where AST was measured in at least 50% of all outpatients in the baseline calendar quarter. Survival models were adjusted for demographic variables, and available clinical and laboratory surrogates of malnutrition-inflammation complex, and cubic survival splines were plotted.

RESULTS

A linear association existed between baseline serum AST levels and mortality. Increasing AST of >20 IU/L was incrementally and almost linearly associated with higher death risk at all levels of adjustment. In fully adjusted models, AST levels of ≥40 IU/L were associated with the highest risk of mortality (hazard ratio: 1.46, 95% CI: 1.38-1.54). Low AST levels (<15 IU/L) were associated with increased death risk only in fully adjusted models examining hepatitis C virus-positive patients.

CONCLUSIONS

Higher AST level of >20 IU/L is incrementally associated with higher mortality in MHD patients whereas AST in the 15-20 IU/L range is associated with the greatest survival. These findings suggest that the assessment of liver function and improving liver disease may confer survival benefit to MHD patients.

Association of incident obstructive sleep apnoea with outcomes in a large cohort of US veterans

RATIONALE

There is a paucity of large cohort studies examining the association of obstructive sleep apnoea (OSA) with clinical outcomes including all-cause mortality, coronary heart disease (CHD), strokes and chronic kidney disease (CKD).

OBJECTIVES

We hypothesised that a diagnosis of incident OSA is associated with higher risks of these adverse clinical outcomes.

METHODS, MEASUREMENTS

In a nationally representative cohort of over 3 million (n=3 079 514) US veterans (93% male) with baseline estimated glomerular filtration rate (eGFR)≥60 mL/min/1.73 m(2), we examined the association between the diagnosis of incident OSA, treated and untreated with CPAP, and: (1) all-cause mortality, (2) incident CHD, (3) incident strokes, (4)incident CKD defined as eGFR<60 mL/min/1.73 m(2), and (5) slopes of eGFR.

MAIN RESULTS

Compared with OSA-negative patients, untreated and treated OSA was associated with 86% higher mortality risk, (adjusted HR and 95% CI 1.86 (1.81 to 1.91) and 35% (1.35 (1.21 to 1.51)), respectively. Similarly, untreated and treated OSA was associated with 3.5 times (3.54 (3.40 to 3.69)) and 3 times (3.06 (2.62 to 3.56)) higher risk of incident CHD; 3.5 times higher risk of incident strokes (3.48 (3.28 to 3.64) and 3.50 (2.92 to 4.19)) for untreated and treated OSA, respectively. The risk of incident CKD was also significantly higher in untreated (2.27 (2.19 to 2.36)) and treated (2.79 (2.48 to 3.13)) patients with OSA. The median (IQR) of the eGFR slope was -0.41 (-2.01 to 0.99), -0.61 (-2.69 to 0.93) and -0.87 (-3.00 to 0.70) mL/min/1.73 m(2) in OSA-negative patients, untreated OSA-positive patients and treated OSA-positive patients, respectively.

CONCLUSIONS

In this large and contemporary cohort of more than 3 million US veterans, a diagnosis of incident OSA was associated with higher mortality, incident CHD, stroke and CKD and with faster kidney function decline.

Association of hepatitis C viral infection with incidence and progression of chronic kidney disease in a large cohort of US veterans

An estimated 4 million Americans have been exposed to the hepatitis C virus (HCV). The risks of incident and progressive chronic kidney disease and of mortality in patients with normal kidney function infected with HCV are unclear. In a nationally representative cohort of 100,518 HCV(+) and 920,531 HCV(-) US veterans with normal baseline estimated glomerular filtration rate (eGFR), we examined the association of HCV infection with (1) all-cause mortality, (2) incidence of decreased kidney function (defined as eGFR <60 mL/min/1.73 m(2) and 25% decrease in eGFR), (3) end-stage renal disease, and (4) rate of kidney function decline. Associations were examined in naive and adjusted Cox models (for time-to-event analyses) and logistic regression models (for slopes), with sequential adjustments for important confounders. Propensity-matched cohort analysis was used in sensitivity analyses. The patients' age was 54.5 ± 13.1 (mean ± standard deviation) years, 22% were black, 92% were male, and the baseline eGFR was 88 ± 16 mL/min/1.73 m(2) . In multivariable adjusted models HCV infection was associated with a 2.2-fold higher mortality (fully adjusted hazard ratio = 2.17, 95% confidence interval [CI] 2.13-2.21), a 15% higher incidence of decreased kidney function (adjusted hazard ratio = 1.15, 95% CI 1.12-1.17), a 22% higher risk of steeper slopes of eGFR (adjusted odds ratio = 1.22, 95% CI 1.19-1.26), and a 98% higher hazard of end-stage renal disease (adjusted hazard ratio = 1.98, 95% CI 1.81-2.16). Quantitatively similar results were found in propensity-matched cohort analyses.

CONCLUSIONS

Infection with HCV is associated with higher mortality risk, incidence of decreased kidney function, and progressive loss of kidney function; randomized controlled trials are warranted to determine whether treatment of HCV infection can prevent the development and progression of chronic kidney disease and improve patient outcomes.

Predictors of treatment with dialysis modalities in observational studies for comparative effectiveness research

BACKGROUND

The Institute of Medicine has identified the comparative effectiveness of renal replacement therapies as a kidney-related topic among the top 100 national priorities. Given the importance of ensuring internal and external validity, the goal of this study was to identify potential sources of bias in observational studies that compare outcomes with different dialysis modalities.

METHODS

This observational cohort study used data from the electronic medical records of all patients that started maintenance dialysis in the calendar years 2007-2011 and underwent treatment for at least 60 days in any of the 2217 facilities operated by DaVita Inc. Each patient was assigned one of six dialysis modalities for each 91-day period from the date of first dialysis (thrice weekly in-center hemodialysis (HD), peritoneal dialysis (PD), less-frequent HD, home HD, frequent HD and nocturnal in-center HD).

RESULTS

Of the 162 644 patients, 18% underwent treatment with a modality other than HD for at least one 91-day period. Except for PD, patients started treatment with alternative modalities after variable lengths of treatment with HD; the time until a change in modality was shortest for less-frequent HD (median time = 6 months) and longest for frequent HD (median time = 15 months). Between 30 and 78% of patients transferred to another dialysis facility prior to change in modality. Finally, there were significant differences in baseline and time-varying clinical characteristics associated with dialysis modality.

CONCLUSIONS

This analysis identified numerous potential sources of bias in studies of the comparative effectiveness of dialysis modalities.

Diagnostic validation and prognostic significance of the Malnutrition-Inflammation Score in nondialyzed chronic kidney disease patients

BACKGROUND

Malnutrition and inflammation are highly prevalent and intimately linked conditions in chronic kidney disease (CKD) patients that lead to a state of protein-energy wasting (PEW), the severity of which can be assessed by the Malnutrition-Inflammation Score (MIS). Here, we applied MIS and validated, for the first time, its ability to grade PEW and predict mortality in nondialyzed CKD patients.

METHODS

We cross-sectionally evaluated 300 CKD stages 3-5 patients [median age 61 (53-68) years; estimated glomerular filtration rate 18 (12-27) mL/min/1.73 m(2); 63% men] referred for the first time to our center. Patients were followed during a median 30 (18-37) months for all-cause mortality.

RESULTS

A worsening in MIS scale was associated with inflammatory biomarkers increase (i.e. alpha-1 acid glycoprotein, fibrinogen, ferritin and C-reactive protein) as well as a progressive deterioration in various MIS-independent indicators of nutritional status based on anthropometrics, dynamometry, urea kinetics and bioelectric impedance analysis. A structural equation model with two latent variables (assessing simultaneously malnutrition and inflammation factors) demonstrated good fit to the observed data. During a follow-up, 71 deaths were recorded; patients with higher MIS were at increased mortality risk in both crude and adjusted Cox models.

CONCLUSIONS

MIS appears to be a useful tool to assess PEW in nondialyzed CKD patients. In addition, MIS identified patients at increased mortality risk.

Better understanding of transplant glomerulopathy secondary to chronic antibody-mediated rejection

Transplant glomerulopathy (TG) is generally accepted to result from repeated episodes of endothelial activation, injury and repair, leading to pathological abnormalities of double contouring or multi-layering of the glomerular basement membrane. TG is a major sequel of chronic active antibody-mediated rejection (cABMR), from pre-existing or de novo anti-HLA antibodies. Hepatitis C infection, thrombotic microangiopathy or other factors may also contribute to TG development. TG prevalence is 5-20% in most series, reaching 55%, in some high-risk cohorts, and is associated with worse allograft outcomes. Despite its prevalence and clinical significance, few well-studied treatment options have been proposed. Similar to desensitization protocols, plasmapheresis with or without immunoabsorption, high-dose intravenous immunoglobulin, rituximab, bortezomib and eculizumab have been proposed in the treatment of TG due to cABMR individually or in various combinations. Robust clinical trials are urgently needed to address this major cause of allograft loss. This review summarizes the current knowledge of the epidemiology, etiology, pathology, and the preventive and treatment options for TG secondary to cABMR.

Sleep apnea is not associated with worse outcomes in kidney transplant recipients

Obstructive sleep apnea(OSA) is one of the most common sleep disorders in kidney transplant recipients, however its long-term consequences have only rarely been investigated. Here, we hypothesized that the presence of OSA would be associated with higher risk of mortality and faster decline of graft function in kidney transplant recipients. In a prospective cohort study 100 prevalent kidney transplant recipients who underwent one-night polysomnography at baseline and were followed for a median 75 months. Generalized linear mixed-effects models and Cox regression models were used to assess the association between OSA and the rate of progression of chronic kidney disease(CKD) and mortality. The estimated slopes of estimated glomerular filtration rate(eGFR) in patients with and without OSA were compared using a two-stage model of eGFR change including only OSA as a variable. In this model patients with OSA (eGFR versus time was −0.93 ml/min/1.73 m²/yr(95%CI:−1.75 to−0.11) had a similar slope as compared to patients without OSA(eGFR versus time was −1.24 ml/min/1.73 m²/yr(95%CI: −1.67 to −0.81). In unadjusted Cox proportional regression analyses OSA was not associated with higher all-cause mortality risk (Hazard Ratio(HR) = 1.20; 95% Confidence Interval(CI): 0.50–2.85). No association was found between the presence of OSA and the rate of progression of CKD or all-cause mortality in prevalent kidney transplant recipients.

Body mass index and mortality in kidney transplant recipients: a systematic review and meta-analysis

BACKGROUND

A higher body mass index (BMI) seems to be linked to survival advantage in maintenance hemodialysis patients. However, it is uncertain if this 'obesity survival paradox' is also observed in kidney transplant recipients. Hence, we systematically reviewed the literature on the impact of pre-transplantation BMI on all-cause mortality in this population.

METHODS

We searched MEDLINE, EMBASE, Web of Science, CINAHL, and Cochrane CENTRAL for relevant studies up to July 2013. Two investigators independently selected the studies using predefined criteria, abstracted the data from the included studies, and independently assessed each study's quality using the Newcastle-Ottawa Quality Assessment Scale. In addition to the qualitative synthesis, we quantitatively pooled the results of the studies with clinical, methodological, and statistical homogeneity.

RESULTS

We screened 7,123 records, from which we included 11 studies (with a total of 305,392 participants) in this systematic review and 4 studies in the meta-analyses. In the only study that included children, obesity was linked to higher mortality in children of 6-12 years old. For adults, our meta-analyses indicated that compared to normal BMI, underweight [Hazard Ratio (HR): 1.09; 95% Confidence Interval (CI): 1.02-1.20], overweight (HR: 1.07; 95% CI: 1.04-1.12), and obese (HR: 1.20; 95% CI: 1.14-1.23) levels of BMI were associated with higher mortality.

CONCLUSION

The presence of the obesity survival paradox is unlikely in kidney transplant recipients since both extremes of pre-transplantation BMI are linked to higher mortality in this population.

Restricting kidney transplant wait-listing for obese patients: let's stop defending the indefensible

The allocation of limited medical resources represents an ethical dilemma that continues to generate lively debates. While the allocation of allografts to wait-listed patients is done in a transparent manner, with its rules open to public debate and prone to continuous improvement, the practice of wait-listing is not centrally regulated, and its rules are often less scrutinized. Denial of kidney transplant wait-listing to obese individuals has been a common practice by most transplant centers. On the face of it, this practice is justified by commonly accepted ethical standards, yet there is now mounting evidence that these justifications do not withstand closer scrutiny. A candid and open debate in the Nephrology and Transplant community is needed to examine the true motivations that underlie the practice of denying wait-listing to obese individuals, and to find a solution that is truly in the best interest of our patients.