Assessment of the Correlation Between Serum Phosphate Level and Muscle Strength as Measured by Handgrip Strength in Patients Treated With Hemodialysis

Abstract

Background: Sarcopenia, commonly observed in patients treated with hemodialysis, correlates with low serum phosphate levels. Although normophosphatemia is desired, dietary phosphate restriction is difficult to achieve and may result in undesirable protein restriction. Objective: We aimed to evaluate whether hyperphosphatemia is associated with higher muscle strength in patients receiving hemodialysis treatment. Design: A single-center prospective observational study. Setting: Ambulatory prevalent patients undergoing hemodialysis treatments in a dialysis unit of a tertiary hospital. Patients: Participants included prevalent patients treated with hemodialysis. All patients were above 18 years. Only patients with residual kidney function below 200 mL/24 hours were included to avoid bias. Measurements: Muscle strength was measured by handgrip strength (HGS). Each patient repeated 3 measurements, and the highest value was recorded. Handgrip strength cutoffs for low muscle strength were defined as <27 kg in men and <16 kg in women. Biochemical parameters, including serum phosphate level, were driven from routine monthly blood tests. Hyperphosphatemia was defined as serum phosphate above 4.5 mg/dL. Methods: Handgrip strength results were compared to nutritional, anthropometric, and biochemical parameters—in particular phosphate level. Long-term mortality was recorded. Results: Seventy-four patients were included in the final analysis. Handgrip strength was abnormally low in 33 patients (44.5%). Patients with abnormal HGS were older and more likely to have diabetes mellitus and lower albumin and creatinine levels. There was no correlation between HGS and phosphate level ( r = 0.008, P = .945). On multivariable analysis, predictors of higher HGS were body mass index and creatinine. Diabetes mellitus and female sex predicted lower HGS. Hyperphosphatemia correlated with protein catabolic rate, blood urea nitrogen, and creatinine. On multivariable analysis, predictors of hyperphosphatemia were higher creatinine level, normal albumin level, and heart failure. During mean follow-up time of 7.66 ± 3.9 months, 11 patients died. Mortality was significantly higher in patients with abnormally low HGS compared with normal HGS (odds ratio = 9.32, P = .02). Limitations: A single-center study. All measurements were performed at one time point without repeated assessments. Direct dietary intake, degree of physical activity, and medication compliance were not assessed. Conclusion: Hyperphosphatemia correlated with increased protein intake as assessed by protein catabolic rate in patients treated with hemodialysis; however, neither correlated with higher muscle strength as measured by HGS. Trial registration: MOH 202125213