Avaliação de sarcopenia em pacientes com doença renal crônica pré-dialítica

Abstract

Sarcopenia is a chronic condition associated with aging characterized by reduced muscle mass, strength and function. The prevalence of sarcopenia in patients with chronic kidney disease (CKD) is increased and is associated with increased morbidity and mortality. In addition, the concomitant occurrence of obesity and muscle loss, a condition defined by sarcopenic obesity (SO), is common in CKD, associated with worse survival and physical function. Computed tomography (CT) and dual-energy x-Ray absorptiometry (DXA) are considered for evaluation of muscle mass, however, cost and difficulty of access are limiting factors for its use. Due to the population aging, it is essential to research new methods for assessing muscle mass, which are more affordable and less costly. Ultrasonography (US) has emerged as a promising method for assessing muscle mass in some populations with chronic diseases, comparable to the evaluation performed by CT. Objectives: To evaluate the prevalence of sarcopenia and sarcopenic obesity in patients with CKD not yet on dialysis, and its associations with clinical, laboratory, inflammatory markers and measures of visceral obesity. In addition, we aimed to investigate the validity and reliability of rectus femoris cross-sectional area (RFCSA) measurement compared to CT in CKD patients not yet on dialysis, and the association between these measurements and the diagnosis of sarcopenia. Methods: A total of 100 patients of both sexes and aged over 65 were evaluated. Sarcopenia was defined by the criteria of the European Working Group on Sarcopenia in Older People (EWGSOP) and of the Foundation for the National Institutes of Health (FNIH) Sarcopenia Project, using DXA to calculate muscle mass. Sociodemographic and clinical data, activities of daily living, functional capacity and level of physical activity were also evaluated. Inflammation was assessed by high-sensitivity C-reactive protein (hsCRP) and interleukin (IL) 4 and 6. Obesity was defined according to the Body Mass Index (BMI), Fat Mass Index (FMI) and the Percentage of Total Body Fat (PTBF). Visceral obesity was evaluated by measures of visceral adipose tissue (VAT) and android fat. For comparison, the patients were divided into groups of non-obese and non-sarcopenic, obese, sarcopenic and obese sarcopenic. RFCSA was assessed using US and CT. Results: The prevalence of sarcopenia was 11.9% and 28.7% using the EWGSOP and FNIH criteria, respectively. Sarcopenia was more prevalent in the more advanced stages of CKD (34.5% in stages 2 and 3A and 65.5% in stages 3B, 4 and 5) and associated with worse performance in activities of daily living (p=0.049), lower walking speed (p<0.001) and higher BMI (p=0.001) in the nonadjusted model. In addition, patients with sarcopenia had lower functional capacity (p=0.012) and higher prevalence of physical inactivity (p=0.041) compared to patients without sarcopenia. After adjusting for confounding variables, sarcopenia was still significantly associated with walking speed (p=0.004) and BMI (p=0.002). HsCRP levels were inversely correlated with lean mass adjusted for BMI (p=0.007) and were also positively associated with BMI (p=0.001). IL4 levels were positively correlated with walking speed (p=0.007) and lean body mass in the lower limbs (p=0.022). The prevalence of obesity was 19.8%, 37.6% and 48.5%, and of SO was 15.8%, 13.9% and 27.7%, when the criteria of BMI, PTBF and FMI were used, respectively. Regarding the metabolic profile, we observed that BMI, FMI, VAT and android fat (p<0.001) were higher in obese and SO patients, using the BMI and FMI obesity criteria. There was an association between measures of visceral obesity with BMI, FMI and stage 4 of CKD. The glomerular filtration rate (GFR) showed a positive correlation with VAT (r=0.311, p=0.002), android fat (r=0.414, p<0.001), BMI (r=0.348, p<0.001) and FMI (r=0,272, p=0,006). The difference in mean RFCSA by US and CT was 3.97 mm, with a strong correlation between the methods (p<0.001). Bland-Altman showed good agreement between CT and US. Based on the definition of low muscle mass according to US of the RFCSA, a sarcopenia prevalence of 12% was observed. Conclusions: Sarcopenia was common in patients with CKD, particularly in the more advanced stages of the disease. We observed an association between levels of inflammatory markers and appendicular lean mass, physical performance and BMI. In addition, obesity and SO were prevalent in patients with CKD, mainly when the FMI obesity criteria was used. There was an association between a worse metabolic profile and visceral obesity measures in obese and SO patients when the BMI and FMI criteria for obesity were used. Regarding CKD, there was an association between GFR and visceral obesity, mainly in stage 4. Finally, US has proven to be a valid and reliable method for assessing RFCSA in patients with CKD not yet on dialysis.