The present study included 116 adult HD patients (35% female, 64 ± 12 years of age) from a single unit of the Meisei-kai Toyo Clinic Yachimata, Chiba, Japan between January 2018 and March 2018. Patients were eligible to participate if they were over 18 years of age, had received maintenance HD at least 3 times per week for more than 6 months, and had no contraindications for BIA including patients with pacemakers or were not limbless. The exclusion criteria of present study were comorbidities active malignancy and recent hospital admission within 3 months that might influence nutritional or functional status. Study collaborators interviewed patients before or during a HD session, obtained recent clinical and laboratory data from medical records, and measured muscle strength and physical performance prior to the start of the HD session. In addition, study collaborators measured the body composition using a BIA after a midweek dialysis session.
Cardiovascular Risk Score
Cardiovascular (CV) risk score was calculated using new risk model developed by Japan Dialysis Outcomes and Practice Patterns Study (J-DOPPS) 6. This CV risk model had a more accurate dose-dependent association with observed CV events than the Framingham risk score among HD patients. The J-DOPPS CV risk model contained only six variables: age, diabetes mellitus, history of CV events, dialysis time per session, phosphorus level, and albumin level, ranging from 0 to 20 points with higher scores reflecting greater risk of CV events.
Diagnosis of Protein-energy Wasting
International Society of Renal Nutrition and Metabolism (ISRNM) criteria were used to identify PEW,7 which has been described elsewhere.8 PEW was scored as the grading of 1 selected item in each of the four categories of wasting syndrome as follows: serum albumin, body mass index (BMI) or unintentional weight loss, pre-dialysis serum creatinine normalized by the body surface area (sCr/BSA), and normalized protein nitrogen appearance (nPNA). The cutoff values were as follows: serum albumin, 3.8 g/dL; BMI, 23 kg/m2 or unintentional weight loss (5% over 3 months or 10% over 6 months); sCr/BSA, 380 μmol/L/m2; and nPNA, 0.8 g/kg per day. BSA was estimated by the following formula:
Body surface (cm2) = [0.425 × (weight)] × [0.725 × (height)] × 0.007184.
A lower value than the cutoff value was scored as 1 point, and the PEW score was calculated as the sum of the four-item score. PEW was defined as a PEW score ≥3 points.
Diagnosis of Frailty
Frailty was evaluated based on the Japanese version of Cardiovascular Health Study (J-CHS) criteria consisting of 5 components: weight loss, exhaustion, low physical activity, slowness and weakness.9 (1) Weight loss was evaluated using the question “Have you lost 2kg or more in the past 6 months?”. (2) Exhaustion was measured using the question: “In the past 2 weeks, have you felt tired without a reason ?”. (3) Low physical activity was measured using the two questions: “Do you engage in moderate levels of physical exercise or sports aimed at health?”, and “Do you engage in low levels of physical exercise aimed at health?”. (4) Slowness was measured using usual gait speed: patients were asked to 5m-walk at their comfortable pace using any walking aids to maintain balance and function. (5) Weakness was evaluated by measuring handgrip strength in the sitting position. The J-CHS comprises the following: (1) Weight loss: 1 point for “yes” to the question; (2) Exhaustion: 1 point for “yes” to the question; (3) Low physical activity: 1 point for “no” to both questions; (4) Slowness: 1point if gait speed < 1.0m/s; (5) Weakness: 1point if handgrip strength < 26kg in men and < 18kg in women. Summing up the J-CHS scores, we calculated a total J-CHS score; a cut off of ≥ 3 was used to identify frailty.
Bioelectrical Impedance Analysis
The seca mBCA515 (seca®, Hamburg, Germany), an integrated platform with a handrail system was used. Electrodes were placed in the ascending handrail, of which two were chosen depending on the subject’s height. Another two pairs of electrodes contacted the soles of the feet. The prediction equations for total body water, and extracellular water (ECW) were validated by a prior study.10 Resistance (R), the opposition of an ionic solution in both intra and extracellular spaces and reactance (Xc), representing the capacitance from cell membranes values obtained at 5 and 50 kHz for different body segments were used in the prediction equations. BIA was performed under standardized conditions according to the manufacturer's protocol. The PA was calculated using the following equation:
PA (degree) =arctan (Xc/R) × (180/π)), is related to body cell mass and soft tissue composition.
Quartiles were obtained for the PA (25th, 3.7°; 50th, 4.2°; 75th, 5.0), and the patients were classified in four groups: first quartile group (PA < 3.7°), second quartile group (3.7 ≤ PA < 4.2°), third quartile group (4.2 ≤ PA < 5.0°), and fourth quartile group (PA ≥ 5.0°).
To examine the PA values adjusting for age, sex, and body mass index, the PA values were converted into s.d. score by the following equation:
Standard deviation score (SDS) = (X – average X)/s.d.
Where X is the observed value, average X is the mean of the normal value at the respective age, sex, and body mass index, and s.d. is the standard deviation from the mean.
Continuous variables are expressed at mean ± standard deviation and as counts and percentages as appropriate. For the comparison of continuous variables among PA groups, one-way analysis of variance was used, and for categorical variables, the Pearson chi-square test was performed. To adjust for effects due to potential confounders for PA, multivariate logistic regression models of PEW, and frailty were performed, and odds ratios (ORs) and 95% confidence intervals (95% CI) were determined. The PA ≥ 5.0° (fourth quartile group) was considered the reference for this analysis. In the analysis for the CV event risk, we compared the CV event risk model score among PA groups using Kruskal-Wallis test. Statistical analyses were performed using SPSS software, version 21, and in all statistical calculations, a two-tailed p < 0.05 was considered statistically significant.