Association of Vitamin D Status with Dual Task Physical Performance in Older Adults

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ObjectiveTo evaluate the association of vitamin D status with age‐related changes in mobility and higher order cognitive function using a single and dual task physical performance test.MethodsAfter consenting, participants completed the baseline assessments that included serum levels of vitamin D, vitals, anthropometrics and body composition, as well as completing surveys to evaluate physical activity, depressive symptoms and fear of falling. Participants performed in random order the physical performance tests, which included 1) walking (single gait task); 2) counting backwards from 50 by 1 (single cognitive task); and 3) walking while counting backwards from 50 by 1 (dual task). The dual task physical performance variables measured were: 1) dual task gait velocity; 2) single task gait velocity; 3) difference in dual and single task gait velocity; 4) dual task counting rate; 5) single task counting rate; 6) difference in dual and single counting rate. Paired t‐tests were used to compare single and dual task variables within the whole population and each vitamin D status group. Spearman's correlations, independent t‐tests, repeated measures ANOVAs and multiple logistic regressions were used to examine the relationship between vitamin D insufficiency (25OHD<30ng/mL) and sufficiency (25OHD≥30ng/mL) and dual task physical performance variables. The significance level was set at α≤0.05, and statistical analyzes were performed using SPSS 21.ResultsThe mean +/− SD of serum vitamin D levels were 30.73 +/− 8.73 ng/ml and 46% of the participants were vitamin D insufficient. Dual and single task counting rate were significantly lower in the vitamin D insufficient group compared to the sufficient group (mean difference: −0.14, P=0.018 and mean difference: −0.06, P=0.028, respectively). Using Spearman correlations, a slower single (r=0.258, P=0.011) and dual counting rate (r=0.278, P=0.006) were significantly associated with vitamin D insufficiency.ConclusionsCognitive performance for dual or single tasking were worse in the vitamin D insufficient group. Since counting backward is a mental tracking task, which is a component of executive function, our results support a relationship between vitamin D insufficiency and executive dysfunction.