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Editorial

Interaction between protein–energy wasting and geriatric nutritional risk index in elderly patients on dialysis

Weng, Shuo-Chun; Tarng, Der-Cherng*

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Journal of the Chinese Medical Association: June 2016 - Volume 79 - Issue 6 - p 299-300
doi: 10.1016/j.jcma.2016.01.004

    Protein–energy malnutrition has been proposed to be a cause of refractory anemia that accompanies the malnutrition–inflammation complex (or cachexia) syndrome in dialysis patients.1 Malnutrition–inflammation complex syndrome and the obesity paradox are also the main etiology for “reverse epidemiology” of cardiovascular risk factors and outcomes in dialysis patients.1,2 However, in some dialysis patients, protein-energy wasting (PEW) is not related to inadequate nutrient intake.3 The 2013 International Society of Renal Nutrition and Metabolism meeting report notes that PEW is responsible for loss of protein mass and fuel reserve, and that PEW is a nonspecific inflammatory process. The term kidney disease wasting emphasizes the strong association between kidney diseases and PEW.3 However, kidney disease wasting does not provide any insight into the different causes of PEW in kidney disease. Moreover, the lack of association between kidney disease (acute kidney injury and chronic kidney disease) and PEW may be found between young (pancreatitis) and elderly individuals (chronic obstructive pulmonary disease) with different etiologies. Therefore, the expert panel reached the conclusion that the term kidney disease wasting is not a suitable substitute for PEW.

    There is a wide variety of causes of PEW and frailty in elderly patients with end-stage renal disease, including genotype, phenotype, comorbid conditions, duration and severity of renal failure, psychosocial problems, and lifestyle, in addition to low anabolic (insulin, growth hormone, and insulin growth factor-1) but high catabolic hormones (parathyroid hormone and glucagon), and age-related mitochondrial dysfunction and oxidative stress.3–6 Numerous different terminologies have been used to describe the phenomena of malnutrition and inflammatory wasting coexisting in patients with kidney diseases, such as uremic malnutrition, protein–energy malnutrition, malnutrition–inflammation atherosclerosis syndrome, and malnutrition–inflammation complex syndrome. Several inflammatory markers, such as C-reactive protein, interleukin-6, tumor necrosis factor-α, interleukin-1, and serum amyloid A, have recently been shown to be associated with concomitant malnutrition and inflammatory wasting.6

    Geriatric Nutritional Risk Index (GNRI) was first used to evaluate malnutrition and related morbidity and mortality in elderly patients.7 It was validated to be a simple and objective screening tool requiring serum albumin, adjusted for ideal body weight and knee height. Recent studies applied GNRI to predict outcomes of heart failure and PEW in maintenance hemodialysis patients.8,9 A wide variety of other instruments have been used for nutritional evaluation, such as the Subjective Global Assessment, Mini Nutritional Assessment-Screening Form, Malnutrition Universal Screening Tool, and Nutritional Risk Screening 2002.8 Physical performance is also an important predictor of outcomes in the elderly and frail people. Chronic kidney disease and end-stage renal disease facilitate the process of wasting before the onset of frank cachexia. The Comprehensive Dialysis Study of the United States Renal Data System investigated the frailty, dialysis initiation, and mortality in maintenance dialysis.10 However, the questionnaires, including the Research ANd Development (RAND) 12-item Short Form, 36-item Kidney Disease Quality of Life symptom scale, and Human Activity Profile via telephone interviews were subjective.10

    Tsai et al11 applied GNRI and demonstrated its long-term predictive value in a prospective cohort of elderly patients who underwent chronic hemodialysis. The authors concluded that patients with a GNRI of < 92 at baseline had significantly increased all-cause mortality during long-term follow-up. In addition, a low body mass index but high erythropoietin resistance index and high-sensitivity C-reactive protein were correlated with a low GNRI. Those patients with a low GNRI also had a low body weight, low body mass index, low serum albumin, low hemoglobin, and high erythropoietin resistance index initially. These variables are compatible with the symptoms of PEW.

    This study had some limitations. First, this was a single-dialysis-unit study and thus could not represent the outcomes of all patients in our nationwide cohort. Second, although GNRI consists of simple objective measurements, the calculated parameter of weight/WLo (Lorentz equations) should be adjusted according to different values for GNRI, albumin, and weight loss.7 It could not be clearly determine whether any modification of the equation through the detailed description was necessary. Third, erythropoietin resistance index is defined as the erythropoietin dose administered per kilogram body weight per week. However, in many studies it has been suggested that the average value be monitored over a 3-month period to determine whether there is any possibility of correctable blood loss or illness.1 Moreover, the erythropoietin responsiveness index with the same calculation was also used.

    The quality of dialysis has greatly improved in Taiwan. We observed the same and improved patterns and percentages of cumulative survival between elderly dialysis patients with a GNRI of ≥ 92 and those with pure frailty without dialysis.10,11 However, the mean age of the pure frailty group was comparatively higher.10 Dialysis may reverse uremia, but residual metabolic derangements, inflammation, comorbid conditions, and the dialysis procedure itself may allow PEW to develop or worsen. Furthermore, it is possible that weight gain may occur while losing muscle, a phenomenon known as sarcopenic obesity, which is an important issue that needs to be addressed.12,13 The time-averaged serum creatinine concentration is a more appropriate surrogate of muscle mass, and changes of serum creatinine over time may represent parallel changes in skeletal muscle mass.13 Nutritional recommendations for the management of sarcopenic obesity are similar to those for PEW, which include exercise (aerobic and resistance), anti-inflammatory strategies, and adequate protein intake.6,14

    Conflicts of interest

    The authors declare that they have no conflicts of interest related to the subject matter or materials discussed in this article.

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