Association Between Alkaline Phosphatase and Muscle Mass, Strength, or Physical Performance in Patients on Maintenance Hemodialysis

Introduction: Alkaline phosphatase (ALP) is an indicator for checking liver or bone disorders, but recent studies have shown the possibility of an additive indicator beyond the simple mineral-bone status in dialysis patients. The aim of the study was to evaluate the ALP level and various indicators for malnutrition, physical performance, or hospitalization in patients on hemodialysis (HD). Methods: This study was an observational study (n = 84). We included all patients undergoing HD with the following criteria: age ≥20 years, duration of dialysis ≥ 6 months, ability to ambulate, ability to communicate, and no hospitalization within the last 3 months before enrollment. Furthermore, none of the patients had liver disease. The patients were divided into tertiles based on the ALP level. Muscle mass (appendicular muscle mass index [ASM/Ht2], thigh muscle area index using computed tomography [TMA/Ht2], strength (handgrip strength [HGS]), and physical performance (gait speed [GS], sit-to-stand for 30-s test [STS30], 6-min walk test [6-MWT], or Short Physical Performance Battery test [SPPB]) were evaluated. The number of hospitalizations was also evaluated. Results: The ALP level in the low, middle, and high tertiles was 50.5 ± 7.5, 69.8 ± 5.4, and 113.3 ± 47.3 IU/l, respectively. The high tertile group showed the poorest trends in ASM/Ht2, TMA/Ht2, HGS, GS, STS30, and 6-MWT compared to the other tertile groups. Logistic regression analysis showed that the high tertile group for low HGS, low GS, or low SPPB had a higher odds ratio compared to the other tertiles. Subgroup analyses according to age, sex and diabetes mellitus showed similar trends as in the total cohort. Hospitalization-free survival rates after 300 days was in the high tertile, and the low or middle tertiles were 53.8% and 77.2%, respectively. Conclusion: The present study demonstrated that ALP is associated with muscle mass, strength, and physical performance in patients on maintenance HD. In addition, the trend showed better hospitalization-free survival in the low or middle tertiles than in the high tertile. ALP can be considered as a simple and useful indicator to detect malnutrition, physical performance, or hospitalization in patients on HD.