The Effect of Vitamin D on Physical Performance and Activities of Daily Living in Independent Community-Dwelling Elderly: Study Protocol

Abstract Background: Despite the high incidence of sunlight, the prevalence of vitamin D deficiency is increasing, especially in the oldest old population. Although observational studies with community-dwelling older adults demonstrate an association between low serum levels of 25(OH)D (Vitamin D) and poor mobility, balance and strength, the results of its supplementation as a strategy to improve physical performance are controversial. The aim of this study is to evaluate the effect of vitamin D on physical performance and functional capacity in community-dwelling oldest old individuals. Methods: This is a longitudinal study with participants of the “Longevos Project” followed from 2010 to 2022. Physical performance was evaluated using the Brazilian version of the Short Physical Performance Battery. For the assessment of handgrip strength, we used a manual dynamometer, adopting the cutoff points of <26 kg for men and <16 kg for women. The assessment of functional capacity was performed using the Katz and Lawton scales adapted for Brazil. Serum vitamin D concentrations were determined via blood tests, with low levels defined as vitamin D <30 ng/mL. Multiple linear regression models will be used to evaluate the simultaneous effects of vitamin D with each variable of physical performance and functional capacity. A significant level of p<0.05 will be adopted. Discussion: The hypothesis of the present study is that low vitamin D levels are associated with worse physical performance and impairment of activities of daily living and that maintaining serum levels of 25(OH)D>30 ng/mL can improve functional capacity.