Increased serum cystatin C is associated with increased mortality in elderly men

Multivariable models using administrative data and biomarkers to adjust for case mix in the ICU

BACKGROUND

Routinely collected laboratory biomarkers could improve control of confounding from disease severity in non-interventional studies of general intensive care unit (ICU) patients. Their ability to predict both short- and long-term mortality was evaluated.

METHODS

The performance of age, sex, Charlson co-morbidity index, and baseline values of ten predefined blood biomarkers as predictors of 30-day and 1-year mortality was evaluated in 5505 general ICU stays.

RESULTS

Regression models based on age, sex, Charlson index, and biomarkers were somewhat less accurate in predicting 30-day mortality (c-index 0.83, Brier score 0.27) compared to the SAPS II score (c-index = 0.88, Brier score = 0.09) and in predicting 1-year mortality (c-index = 0.82, Brier score = 0.31) compared to the SAPS II score (c-index = 0.85, Brier score = 0.13). Cystatin C improved predictive ability slightly compared to creatinine, but age and Charlson comorbidity index were more important predictors. Using multiple imputation to replace missing biomarker values notably improved predictive ability of the models.

CONCLUSIONS

Automatically collected baseline variables are almost as predictive of both short- and long-term mortality in general ICU patients, as the SAPS II score. This can facilitate internal control of confounding in non-interventional studies of mortality using administrative data.

Renal function is a determinant of subjective well-being in active seniors but not in patients with subjective memory complaints

BACKGROUND

During our whole life span, factors influencing health and functioning are accumulated. In chronic kidney disease, quality of life is adversely affected. We hypothesized that biomarkers of renal function could also be determinants of subjective well-being (SWB) in Swedish elderly subjects. SWB was assessed by the Psychological General Well-Being index (PGWB index) in two study groups: Active seniors (AS) consisted of community-dwelling elderly Swedes leading an active life (n = 389), and the DGM cohort (n = 300) consisted of subjects referred to the Memory Unit at the Department of Geriatrics for memory problems, Serum creatinine, cystatin C, and eGFR (CKD-EPI) were used as biomarkers of renal function.

RESULTS

There were no significant differences in cystatin C and eGFR values between the two cohorts: cystatin C medians 0.88 vs 0.86 mg/L and eGFR 73 vs 80 mL/min/1.73 m2 (AS vs DGM). In the AS cohort cystatin C was negatively related to PGWB index in women (P < 0.001, R2 ≈ 5%), and the covariates age and BMI did not improve the models. The renal biomarkers were unrelated to the PGWB index in the DGM cohort. Cystatin C in the AS cohort was adversely related to the PGWB subdimensions anxiety, depressed mood, positive well-being, and vitality in women, but in men only to depressed mood (P < 0.006; R2 ≈ 6%). In the DGM cohort, depressed mood in men was also significantly related to cystatin C (P = 0.050), but not in women.

CONCLUSIONS

Renal function even within the normal range, measured by serum cystatin C concentration, has significant and sex specific associations with subjective well-being and its subdimensions in healthy elderly subjects. Maintenance of good renal function in aging may be of importance in maintaining a high subjective well-being.

Cystatin C: a new renal marker and its potential use in small animal medicine

The occurrence of chronic kidney disease is underestimated in both human and veterinary medicine. Glomerular filtration rate (GFR) is considered the gold standard for evaluating kidney function. However, GFR assessment is time-consuming and labor-intensive and therefore not routinely used in practice. The commonly used indirect GFR markers, serum creatinine (sCr) and urea, are not sufficiently sensitive or specific to detect early renal dysfunction. Serum cystatin C (sCysC), a proteinase inhibitor, has most of the properties required for an endogenous GFR marker. In human medicine, numerous studies have evaluated its potential use as a GFR marker in several populations. In veterinary medicine, this marker is gaining interest. The measurement is easy, which makes it an interesting parameter for clinical use. This review summarizes current knowledge about cystatin C (CysC) in humans, dogs, and cats, including its history, assays, relationship with GFR, and biological and clinical variations in both human and veterinary medicine.

Urinary neutrophil gelatinase-associated lipocalin (NGAL) is associated with mortality in a community-based cohort of older Swedish men

OBJECTIVE

Neutrophil gelatinase-associated lipocalin (NGAL) indicates tubular kidney damage, neutrophil activation and possibly atherogenesis, however the prospective association between urinary NGAL (u-NGAL) and cardiovascular death in the community is not known.

METHODS

This study evaluates the association between urinary and serum NGAL and mortality in a Swedish population of 597 men aged 78 years. During the study (median follow-up 8.1 years) 261 men died, 90 of cardiovascular causes.

RESULTS

U-NGAL was associated with increased all-cause and cardiovascular mortality (HR 2.0 for quartile 4 vs. quartile 1, 95% CI 1.0-4.0, P < 0.05) in Cox regression models independently of cardiovascular risk factors, CRP and cystatin C estimated glomerular filtration rate (eGFRCysC) but not urinary Albumin (u-Alb). A combination of low eGFRCysC (≤60 mL/min), high u-Alb (≥3 mg/mmol Cr) and high u-NGAL (≥1.19 μg/mmol Cr) was associated with a 9-fold increased cardiovascular mortality (P < 0.001) and a 3-fold increased all-cause mortality (P < 0.001). Serum NGAL was associated with increased all-cause mortality risk independent of other cardiovascular risk factors (HR 1.4 for quartile 4 vs.1, 95% CI 1.0-1.9, P < 0.05) but not after adjustment with CRP, eGFRCysC or u-Alb.

CONCLUSION

This community study is the first to show that the tubular kidney biomarker u-NGAL associated with increased cardiovascular and all-cause mortality independent of cardiovascular risk factors and glomerular filtration. Additional research is needed to evaluate the utility of NGAL in clinical practice.

Significant differences when using creatinine, modification of diet in renal disease, or cystatin C for estimating glomerular filtration rate in ICU patients

BACKGROUND

Renal dysfunction is associated with increased morbidity and mortality in intensive care patients. In most cases the glomerular filtration rate (GFR) is estimated based on serum creatinine and the Modification of Diet in Renal Disease (MDRD) formula, but cystatin C-estimated GFR is being used increasingly. The aim of this study was to compare creatinine and MDRD and cystatin C-estimated GFR in intensive care patients.

METHODS

Retrospective observational study was performed, on patients treated within the general intensive care unit (ICU) during 2004-2006, in a Swedish university hospital.

RESULTS

GFR markers are frequently ordered in the ICU; 92% of the patient test results had cystatin C-estimated GFR (eGFR(cystatinC)) ≤ 80 mL/min/1.73 m(2), 75% had eGFR ≤ 50 mL/min/1.73 m(2), and 30% had eGFR ≤ 20 mL/min/1.73 m(2). In contrast, only 46% of the patients had reduced renal function assessed by plasma creatinine alone, and only 47% had eGFR(MDRD) ≤ 80 mL/min/1.73 m(2). The mean difference between eGFR(MDRD) and eGFR(cystatinC) was 39 mL/min/1.73 m(2) for eGFR(cystatinC) values ≤ 60 mL/min/1.73 m(2).

CONCLUSIONS

GFR is commonly assessed in the ICU. Cystatin C-estimated GFR yields markedly lower GFR results than plasma creatinine and eGFR(MDRD). Many pharmaceuticals are eliminated by the kidney, and their dosage is adjusted for kidney function. Thus, the differences in GFR estimates by the methods used indicate that the GFR method used in the intensive care unit may influence the treatment.

Screening for chronic kidney disease in HIV-infected patients

With improved survival afforded by highly active antiretroviral therapy (HAART), CKD has emerged as one of the primary comorbid conditions affecting HIV-infected individuals. Although CKD in HIV-infected individuals is classically thought of as a consequence of advanced HIV infection such as in the case of HIV-associated nephropathy, several factors likely contribute to the development CKD in HIV infection. These factors include genetic predisposition, age-related decline in kidney function, HAART-related metabolic changes, exposure to multiple nephrotoxic medications, and concurrent conditions such as hepatitis C or illicit drug use. Similar to the general population, proteinuria and impaired kidney function are associated with faster progression to acquired immune deficiency syndrome and death. Given the prevalence and impact of kidney disease on the course of HIV infection and its management, current guidelines recommend screening all HIV-infected individuals for kidney disease. This review focuses on the current guidelines for kidney disease screening and discusses traditional as well as promising strategies for detecting CKD in this vulnerable population.

[Renal function evaluation methods in the elderly: reliability and clinical implications]

Chronic renal disease (CRD) is found in a third of the Spanish population aged more than 65 years old. Detection and early treatment would increase survival and help to reduce associated cardiovascular morbidity and mortality as well as the risk of pharmacological iatrogeny. Determination of the glomerular filtration rate has traditionally been considered the best parameter for renal function evaluation, which should not be based exclusively on serum creatinine concentration or creatinine clearance. The application of predictive equations is useful in the diagnosis, classification and outpatient management of patients with CRD. Most studies performed in the elderly have found that the Modification of Diet in Renal Disease (MDRD-4) has greater precision and accuracy than the Cockcroft-Gault formula, and is considered the nomogram of choice in this age group. The Cockcroft-Gault formula can be used when rapid estimation of renal function or drug adjustments are required, so long as the limitations of this method are taken into account.

Serum cystatin C and the risk of Alzheimer disease in elderly men

BACKGROUND

Multiple lines of research suggest that increased cystatin C activity in the brain protects against the development of Alzheimer disease (AD).

METHODS

Serum cystatin C levels were analyzed at two examinations of the Uppsala Longitudinal Study of Adult Men, a longitudinal, community-based study of elderly men (age 70 years, n = 1,153 and age 77 years, n = 761, a subset of the age 70 examination). Cox regressions were used to examine associations between serum cystatin C and incident AD. AD cases were identified by cognitive screening and comprehensive medical chart review in all subjects.

RESULTS

On follow-up (median 11.3 years), 82 subjects developed AD. At age 70 years, lower cystatin C was associated with higher risk of AD independently of age, APOE4 genotype, glomerular filtration rate, diabetes, hypertension, stroke, cholesterol, body mass index, smoking, education level, and plasma amyloid-beta protein 40 and 42 levels (hazard ratio [HR] for lowest [<1.12 micromol/L] vs highest [>1.30 micromol/L] tertile = 2.67, 95% CI 1.22-5.83, p < 0.02). The results were similar at age 77 years (43 participants developed AD during follow-up). Furthermore, a 0.1-mumol/L decrease of cystatin C between ages 70 and 77 years was associated with a 29% higher risk of incident AD (HR 1.29, 95% CI 1.03-1.63, p < 0.03).

CONCLUSIONS

Low levels of serum cystatin C precede clinically manifest Alzheimer disease (AD) in elderly men free of dementia at baseline and may be a marker of future risk of AD. These findings strengthen the evidence for a role for cystatin C in the development of clinical AD.

The normal ageing kidney – morphology and physiology

This paper will review some fundamentals of normal renal physiology necessary to understand the changes occurring with age and enable the reader to distinguish between chronic renal insufficiency and the consequences of normal ageing on kidney function.

Use of multiple biomarkers to improve the prediction of death from cardiovascular causes

BACKGROUND

The incremental usefulness of adding multiple biomarkers from different disease pathways for predicting the risk of death from cardiovascular causes has not, to our knowledge, been evaluated among the elderly.

METHODS

We used data from the Uppsala Longitudinal Study of Adult Men (ULSAM), a community-based cohort of elderly men, to investigate whether a combination of biomarkers that reflect myocardial cell damage, left ventricular dysfunction, renal failure, and inflammation (troponin I, N-terminal pro-brain natriuretic peptide, cystatin C, and C-reactive protein, respectively) improved the risk stratification of a person beyond an assessment that was based on the established risk factors for cardiovascular disease (age, systolic blood pressure, use or nonuse of antihypertensive treatment, total cholesterol, high-density lipoprotein cholesterol, use or nonuse of lipid-lowering treatment, presence or absence of diabetes, smoking status, and body-mass index).

RESULTS

During follow-up (median, 10.0 years), 315 of the 1135 participants in our study (mean age, 71 years at baseline) died; 136 deaths were the result of cardiovascular disease. In Cox proportional-hazards models adjusted for established risk factors, all of the biomarkers significantly predicted the risk of death from cardiovascular causes. The C statistic increased significantly when the four biomarkers were incorporated into a model with established risk factors, both in the whole cohort (C statistic with biomarkers vs. without biomarkers, 0.766 vs. 0.664; P<0.001) and in the group of 661 participants who did not have cardiovascular disease at baseline (0.748 vs. 0.688, P=0.03). The improvement in risk assessment remained strong when it was estimated by other statistical measures of model discrimination, calibration, and global fit.

CONCLUSIONS

Our data suggest that in elderly men with or without prevalent cardiovascular disease, the simultaneous addition of several biomarkers of cardiovascular and renal abnormalities substantially improves the risk stratification for death from cardiovascular causes beyond that of a model that is based only on established risk factors.

Effect of sibutramine on weight reduction in women with polycystic ovary syndrome: a randomized, double-blind, placebo-controlled trial

OBJECTIVE

To examine the efficacy of sibutramine together with brief lifestyle modification for weight reduction in obese women with polycystic ovary syndrome (PCOS).

DESIGN

Investigator-initiated, multicenter, double-blind, randomized, parallel-group clinical trial.

SETTING

Departments of Obstetrics and Gynecology in primary care, referral centers, and private practice.

PATIENT(S)

Forty-two patients with confirmed PCOS were included in the study, and 34 patients completed the study.

INTERVENTION

Sibutramine 15 mg once daily together with brief lifestyle modification was compare with placebo together with brief lifestyle modification.

MAIN OUTCOME MEASURE(S)

The primary endpoint was to assess weight loss. Secondary endpoints included the efficacy of sibutramine for treatment of menstrual pattern and cardiovascular risk factors.

RESULT(S)

After 6 months the sibutramine group had lost 7.8 +/- 5.1 kg compared with a weight loss of 2.8 +/- 6.2 kg in the placebo group. Sibutramine treatment resulted in significant decreases in apolipoprotein B, apolipoprotein B/apolipoprotein A ratio, triglycerides, and cystatin C levels.

CONCLUSION(S)

Sibutramine in combination with lifestyle intervention results in significant weight reduction in obese patients with PCOS. In addition to the weight loss, sibutramine seems to have beneficial effects on metabolic and cardiovascular risk factors.

Biomarkers related to aging in human populations

Biomarkers are increasingly employed in empirical studies of human populations to understand physiological processes that change with age, diseases whose onset appears linked to age, and the aging process itself. In this chapter, we describe some of the most commonly used biomarkers in population aging research, including their collection, associations with other markers, and relationships to health outcomes. We discuss biomarkers of the cardiovascular system, metabolic processes, inflammation, activity in the hypothalamic-pituitary axis (HPA) and sympathetic nervous system (SNS), and organ functioning (including kidney, lung, and heart). In addition, we note that markers of functioning of the central nervous system and genetic markers are now becoming part of population measurement. Where possible, we detail interrelationships between these markers by providing correlations between high risk levels of each marker from three population-based surveys: the National Health and Nutrition Examination Survey (NHANES) III, NHANES 1999-2002, and the MacArthur Study of Successful Aging. NHANES III is used instead of NHANES 1999-2002 when specific markers of interest are available only in NHANES III and when we examine the relationship of biomarkers to mortality which is only known for NHANES III. We also describe summary measures combining biomarkers across systems. Finally, we examine associations between individual markers and mortality and provide information about biomarkers of growing interest for future research in population aging and health.

Concomitant drugs with exposure to contrast media

The increasing number of radiological procedures performed in old patients with high co-morbidity may be one of the problems physicians have to deal with when regarding the increasing number of acute renal failures. A key question when addressing the patients scheduled to receive iodinated contrast media (CM) is which concomitant medications prescribed to the patient are potentially harmful or helpful in terms of the risk of contrast-induced nephropathy. This overview summarizes the knowledge of concomitant medications in the setting of CM application and gives suggestion for prescription. In general, due to the unique (yet not fully understood and of high complexity) mechanism of renal damage proposed for a variety of nephrotoxic drugs including CM, physicians should carefully monitor patients' renal function and hydration status whenever concomitant nephrototoxic drugs are used. Recommendations are to monitor kidney function with more sensitive measurements of glomerular filtration rate (i.e. cystatin C).