Vitamin D deficiency: cognition, mortality and resource utilisation - prospective associations

Abstract

Introduction: The association between Vitamin D and bone health has long been known. In recent times there has been increasing research into the effects of Vitamin D beyond this well-established link. Although there has been extensive work completed, the results have been variable to date. Aims: The aim of this body of work was to prospectively assess the extra-osseous associations of Vitamin D in an older Irish population who are at significant risk of Vitamin D deficiency. The areas of interest include all-case mortality, resource utilisation, including hospital admission, Emergency Department (ED) attendance and cognition. Methods: These studies come from prospectively determining outcomes for participants of the TUDA study some five years later. The TUDA study was a large cross sectional study from Northern and Southern Ireland that compared cognition and diet in a community population from three disease-defined cohorts (mild cognitive impairment (MCI), hypertension and osteoporosis). Four individual studies were conducted to evaluate the relationship between Vitamin D and mortality, hospital admission and Emergency Department (ED) attendances and cognition. The 3,093 participants included were the TUDA cohorts recruited between 2008 and 2012 through Saint James's Hospital (from the MCI and osteoporosis cohort) and outcomes were assessed between 2013 and 2015. Results: During the follow-up period of four years, 40% of participants were admitted, 51% attended the Emergency Department and 15% died. In the three studies looking at mortality or hospital attendance, Vitamin D was inversely related to all the outcomes of interest. Vitamin D deficiency was not associated with cognitive change over time in four of the five RBANS Indices. Performance on Index IV improved significantly in cases. All statistical models were adjusted for multiple covariates including potential confounders of Vitamin D, frailty and chronic medical conditions. Conclusion: These studies add to a growing literature that shows prospective associations between Vitamin D deficiency and poor outcome measures in relation to mortality and resource utilisation. The improvement in RBANS Index IV in patients who were initially Vitamin D deficient may have been a chance effect or may reflect a benefit in cognitive function with repletion of deficient Vitamin D levels over time. All associations were independent of markers of cognitive and physical frailty. These results support an effect of Vitamin D beyond falls and bone health. The need for further evaluation of Vitamin D deficiency and supplementation, as a modifiable factor in processes beyond the current recommendations for bone health, is warranted and should focus on randomised controlled trials.