Asymmetric Dimethylarginine,Race, and Mortality in Hemodialysis Patients

Background and objectives

Levels of asymmetric dimethylarginine, an inhibitor of nitric oxide synthase, are elevated in kidney disease and associated with mortality in white European hemodialysis populations. Nitric oxide production and degradation are partially genetically determined and differ by racial background. No studies have measured asymmetric dimethylarginine in African Americans on dialysis and assessed whether differences exist in its association with mortality by race.

Design, setting, participants, & measurements

Asymmetric dimethylarginine was measured in 259 patients on maintenance hemodialysis assembled from 2004 to 2012 in Boston area outpatient centers. Cox proportional hazards models were used to determine the association between asymmetric dimethylarginine and all-cause mortality, and an interaction with race was tested.

Results

Mean (SD) age was 63 (17) years, 46% were women, and 22% were African American. Mean asymmetric dimethylarginine in non–African Americans was 0.79 µmol/L (0.16) versus 0.70 µmol/L (0.11) in African Americans (P<0.001); 130 patients died over a median follow-up of 2.3 years. African Americans had lower mortality risk than non–African Americans (hazard ratio, 0.27; 95% confidence interval, 0.15 to 0.50) that was robust to adjustment for age, comorbidity, and asymmetric dimethylarginine (hazard ratio, 0.35; 95% confidence interval, 0.17 to 0.69). An interaction was noted between race and asymmetric dimethylarginine (P=0.03), such that asymmetric dimethylarginine was associated with higher mortality in non–African Americans (adjusted hazard ratio, 1.29; 95% confidence interval, 1.06 to 1.57 per 1 SD higher asymmetric dimethylarginine) but not in African Americans (adjusted hazard ratio, 0.57; 95% confidence interval, 0.28 to 1.18). Additional adjustment for fibroblast growth factor 23 partially attenuated the association for non–African Americans (adjusted hazard ratio, 1.22; 95% confidence interval, 0.98 to 1.50).

Conclusions

African Americans have lower asymmetric dimethylarginine levels and lower hazard for mortality compared with non–African Americans. Levels of asymmetric dimethylarginine did not explain lower hazard for mortality in non–African American patients. High asymmetric dimethylarginine was a risk factor for mortality exclusively in non–African Americans. Mechanisms explaining these relationships need to be evaluated.     

Dose finding with drug combinations in cancer phase I clinical trials using conditional escalation with overdose control

We present a Bayesian adaptive design for dose finding of a combination of two drugs in cancer phase I clinical trials. The goal is to estimate the maximum tolerated dose (MTD) as a curve in the two‐dimensional Cartesian plane. We use a logistic model to describe the relationship between the doses of the two agents and the probability of dose limiting toxicity. The model is re‐parameterized in terms of parameters clinicians can easily interpret. Trial design proceeds using univariate escalation with overdose control, where at each stage of the trial, we seek a dose of one agent using the current posterior distribution of the MTD of this agent given the current dose of the other agent. At the end of the trial, an estimate of the MTD curve is proposed as a function of Bayes estimates of the model parameters. We evaluate design operating characteristics in terms of safety of the trial design and percent of dose recommendation at dose combination neighborhoods around the true MTD curve. We also examine the performance of the approach under model misspecifications for the true dose–toxicity relationship. Copyright © 2014 John Wiley & Sons, Ltd.     

Schizophrenia, substance use disorders and medical co-morbidity

OBJECTIVES: This study compared medical treatment costs of adults with schizophrenia to adults with both substance use disorders and schizophrenia. METHODS: This cross-sectional observational study used a paid claims data base to identify 6884 adults treated for schizophrenia. Twenty percent of these also had substance use disorder. We report the costs and likelihood of hospitalization for eight common medical diseases, and the categories of injuries and poisoning, and ill defined conditions. Multivariate analyses were used to adjust rates of treatment for age and sex differences in the comparison groups. RESULTS: There were higher rates of treatment for five of the eight medical disorders, higher treatment costs for two of the medical disorders and much higher costs for psychiatric treatment among those with comorbid substance use disorders. Both groups had high rates of treatment in the categories of injury and poisoning and ill defined conditions. CONCLUSIONS: Closer working relationships among mental health and medical professionals are needed to care for those with schizophrenia and substance use disorders: first, greater attention to the treatment of substance use disorders may improve the health status of those with schizophrenia, reduce their costly medical and psychiatric care and stabilize their psychiatric condition, and second, continuity of care among professionals may promote willingness to seek medical attention or alleviate misunderstandings when adults with schizophrenia present with medical problems.     

Use of a state inpatient forensic system under managed mental health care

OBJECTIVES: One of the goals of managed mental health care has been to lower the use of inpatient psychiatric treatment. In the past, interventions that have limited hospitalization for persons with severe mental illness have led to greater involvement of these individuals with the criminal justice and forensic mental health systems. The authors examined associations between Medicaid managed mental health care in Massachusetts and rates of admission to the inpatient forensic mental health service maintained by the state's mental health department. METHODS: A total of 7,996 persons who were receiving services from the department before and after the introduction of managed care were studied. A logistic regression model based on generalized estimating equations was used to identify associations between Medicaid beneficiary status and forensic hospitalization before and after the introduction of managed care. RESULTS: The overall rate of forensic hospitalization declined in the study cohort in both periods. However, no significant decline was observed in the risk of forensic hospitalization among Medicaid beneficiaries whose care had become managed. CONCLUSIONS: Although the results of this study warrant further exploration, the risk of forensic hospitalization among Medicaid beneficiaries should be considered by policy makers in the design of mental health system interventions.     

Anemia as a risk factor for cardiovascular disease and all-cause mortality in diabetes: the impact of chronic kidney disease

Anemia is a potential nontraditional risk factor for cardiovascular disease (CVD). This study evaluated whether anemia is a risk factor for adverse outcomes in people with diabetes and whether the risk is modified by the presence of chronic kidney disease (CKD). Persons with diabetes from four community-based studies were pooled: Atherosclerosis Risk in Communities, Cardiovascular Health Study, Framingham Heart Study, and Framingham Offspring Study. Anemia was defined as a hematocrit <36% in women and <39% in men. CKD was defined as an estimated GFR of 15 to 60 ml/min per 1.73 m(2). Study outcomes included a composite of myocardial infarction (MI)/fatal coronary heart disease (CHD)/stroke/death and each outcome separately. Cox regression analysis was used to study the effect of anemia on the risk for outcomes after adjustment for potential confounders. The study population included 3015 individuals: 30.4% were black, 51.6% were women, 8.1% had anemia, and 13.8% had CKD. Median follow-up was 8.6 yr. There were 1215 composite events, 600 MI/fatal CHD outcomes, 300 strokes, and 857 deaths. In a model with a CKD-anemia interaction term, anemia was associated with the following hazard ratios (95% confidence intervals) in patients with CKD: 1.70 (1.24 to 2.34) for the composite outcome, 1.64 (1.03 to 2.61) for MI/fatal CHD, 1.81 (0.99 to 3.29) for stroke, and 1.88 (1.33 to 2.66) for all-cause mortality. Anemia was not a risk factor for any outcome in those without CKD (P > 0.2 for all outcomes). In persons with diabetes, anemia is primarily a risk factor for adverse outcomes in those who also have CKD.     

Level of kidney function as a risk factor for cardiovascular outcomes in the elderly

BACKGROUND: There is a high prevalence of both reduced kidney function as well as cardiovascular disease (CVD) in the elderly. We evaluated whether the level of kidney function is an independent risk factor for CVD outcomes in the Cardiovascular Health Study (CHS), a cohort of subjects whose age at baseline was 65 years old or older. METHODS: Cox proportional-hazards regression was used to evaluate the association of predicted glomerular filtration rate (GFR) with CVD after adjustment for the major CVD risk factors. We searched for nonlinear relationships between GFR and CVD, as well as interactions between level of kidney function and major CVD risk factors on CVD. RESULTS: A total of 4893 subjects with predicted GFR of 15 to 130 mL/min/1.73 m2 were included in the analysis. Fifty-six percent were female and the mean age was 73.4 years. Of the subjects, 549 (11.2%) died and 1229 (25.1%) experienced CVD events in 5.05 years of follow-up. Each 10 mL/min/1.73 m2 lower GFR was associated with an adjusted hazard ratio for CVD, de novo CVD, recurrent CVD and all-cause mortality of 1.05 (1.02, 1.09), 1.07 (1.01, 1.12), 1.04 (0.99, 1.09), and 1.06 (1.00, 1.12), respectively. There was no significant interaction between level of GFR and other traditional CVD risk factors on CVD outcomes. A linear model best described the relationship between GFR and CVD. CONCLUSION: The level of GFR is an independent risk factor for CVD, de novo CVD, and all-cause mortality in the elderly.