The Combined Effect of Vitamin D Deficiency and Hyperparathyroidism on Postural Stability among Healthy Adult Males.

ABSTRACT

BACKGROUND AND OBJECTIVE: Vitamin D has been shown to improve muscle strength and bone health; consequently, be important for maintaining good balance. Possible risk factors related to postural stability in young adults still underdetermined. However, this study was designed to determine the effect of vitamin D status on postural stability. MATERIALS AND METHODS: A cross-sectional study of 704 healthy young adult males were enrolled in this study. Dynamic balance was measured as overall stability index (OSI) using biodex balance system (BBS). Vitamin D deficiency was defined when its serum level <20 ng mL-1. The effect size was measured for vitamin D, parathyroid hormone (PTH) and the interaction between vitamin D and PTH (VTD*PTH) with respect to the OSI values. Correlations between variables were examined according to the beta standardised coefficient (ß) and the effect size was measured using the partial eta-squared (η2) test. RESULTS: About 95, 3.8 and 1.2% of individuals had deficient, insufficient and normal vitamin D levels, respectively. Vitamin D had no significant effect to OSI, but PTH exhibited a significant correlation with OSI (adjusted ß = 0.095, p = 0.038). A significant effect size was observed between OSI and PTH (adjusted partial η2 = 0.012, p = 0.038) and between OSI and VTD*PTH (adjusted partial η2 = 0.034, p<0.001). CONCLUSION: A significant interaction of vitamin D deficiency and high PTH on postural stability is detected among healthy adult males.