Association Between Vitamin D Level and Biomechanical Characteristics of Proximal Muscles

Aim: The aim of the present study was to evaluate the association of 25(OH)D level with the strength and the biomechanical characteristics (tone, elasticity and stiffness) of the proximal muscles in patients aged 65 years and older. Materials and Method: A hundred and nine patients aged ≥65 years were included to the study. Proximal muscles were evaluated in terms of muscle strength and biomechanical features (tone, elasticity, and stiffness). Strength measurement was performed by MicroFET3, whilst biomechanical properties were assessed by MyotonPRO device. Physical performance was evaluated by using a standardized questionnaire and the Timed Up and Go test (TUG). Serum 25(OH)D levels were measured by high performance liquid chromatography (HPLC). Comparative analysis of muscle parameters was carried out between vitamin D sufficient and deficient groups. ROC curve analysis was performed in order to the evaluate the potential role of MicroFET3-measured proximal muscle strength in determining vitamin D status. Results: The study group consisted of 109 patients (88 female, 21 male) with a mean age of 71.2±4.6 years. Muscles strength was statistically higher in the sufficient group (p<0.005). The quadriceps elasticity at the non-dominant site and bilateral hamstring muscle elasticity were significantly greater in vitamin D sufficient patients (p<0.01, p<0.05 for quadriceps and hamstring muscles, respectively). Physical performance of the sufficient group was statistically higher than the vitamin D deficient participants (p<0.05). Last but not least, ROC analysis indicated that measures of proximal muscle strength had acceptable levels of accuracy (Area Under Curve >0.70) in discriminating the patient's vitamin D sufficiency. Conclusion: Proximal muscle strength, elasticity and physical performance are associated with vitamin D status. Proximal muscle strength is a predictor of vitamin D sufficiency with moderate accuracy. Keywords: elderly, muscle strength, muscle tonus, vitamin D