Title : The relationship between serum vitamin D and the muscle fitness in patients receiving maintained haemodialysis
Background: Traditionally, vitamin D is thought to be related to the health of bone and metabolism of calcium and phosphorus. Recently, the effect of extra-bone in vitamin D has become a new research point. Because of renal failure, patients undergoing maintained haemodialysis (MHD) may have a decrease of serum vitamin D. Muscle fitness, which include the normal level of muscle mass, muscle strength and physical activity, has also become a hot topic in MHD patients. And the previous study of ours found a decrease of appendicular muscle mass in MHD patients, which was also an important predictive factor of death of these patients.
Aim: To explore the relationship between vitamin D and muscle fitness of maintained haemodialysis patients.
Methods: A cross-sectional study. The serum vitamin D was tested by the method of electrochemiluminescence. Muscle mass was measured by bioelectrical impedance technology and presented as the appendicular muscle mass. The muscle strength was measured by the Jamar digital hand dynamometer to test the grip strength. The physical activity was measured through 4-m usual walking speed test to assess the gait speed.
Results: Of the 155 MHD patients, twelve patients (7.7%) had a sufficient level of serum vitamin D, thirty-seven patients (23.9%) had an insufficient level and one hundred and six patients (68.4%) had a level of vitamin D under 20ng/ml which was defined as deficiency. According to the standard of European Working Group on Sarcopenia in Older People (PWGSOP), taking the muscle fitness of healthy Chinese people as the reference, the percentage of decreased appendicular muscle mass, grip strength and gait speed of the MHD patients was 41.9%, 20.6% and 32.9%, respectively. The correlation analysis showed that the level of serum vitamin D was positively correlated to appendicular muscle mass (r=0.199, p=0.013), grip strength (r=0.311, p<0.0001) and the gait speed (r=0.251, p=0.002).
Conclusion: The deficiency of vitamin D is quite common in Chinese MHD patients. And they also suffer a decrease of muscle fitness at the same time. Increasing the level of serum vitamin D might be a new and efficient way to improve the muscle fitness of MHD patients, which may, in turn, have some help in improving the quality of life of MHD patients.