Alzheimers Res Ther

BACKGROUND: Vitamin D deficiency is associated with an increased risk of Alzheimer's disease and increased beta-amyloid (Abeta) in animals. Hence we sought to investigate the relationship between plasma 25-hydroxyvitamin D (25(OH)D) and cerebral Abeta in older adults with subjective memory complaints. METHODS: This is a secondary analysis of the Multidomain Alzheimer Preventive Trial. Participants were 178 dementia-free individuals aged 70 years or older with data on plasma 25(OH)D and cerebral Abeta load assessed by [(18)F]-florbetapir positron emission tomography. Plasma 25(OH)D was measured at study baseline using a commercially available electro-chemiluminescence competitive binding assay. Standard uptake value ratios (SUVRs) were generated using the cerebellum as a reference. Brain regions assessed included the cortex, anterior cingulate, anterior putamen, caudate, hippocampus, medial orbitofrontal cortex, occipital cortex, parietal cortex, pons, posterior cingulate, posterior putamen, precuneus, semioval centre and temporal cortex. Associations were explored using fully adjusted multiple linear regression models. RESULTS: Participants had a mean (SD) age of 76.2 years (4.4) and 59.6% were female. The mean (SD) plasma 25(OH)D level was 22.4 ng/ml (10.8) and the mean (SD) cortical SUVR was 1.2 (0.2). We did not find any cross-sectional associations (p > 0.05) between baseline 25(OH)D levels and Abeta in any of the brain regions studied. CONCLUSIONS: These preliminary results suggest that circulating 25(OH)D is not associated with cerebral Abeta in older adults. Further longitudinal studies with the measurement of mid-life vitamin D status are required to explore the relationship between vitamin D and Abeta accrual over time, thereby circumventing the shortfalls of a cross-sectional study

Specific Considerations Relevant to Critical Illness

Only recently it has been recognized that vitamin D, which in reality is a steroid prohormone, may be of great interest to various aspects of critical illness not only because of its classic function in the regulation of calcium homeostasis but of its suspected pleiotropic effects. Since 2011, several observational studies have demonstrated a strong association between vitamin D deficiency and adverse outcomes, specifically higher mortality in this vulnerable population. The major current vitamin D and nutrition guidelines do not specifically address vitamin D requirements of critically ill patients, and typical nutrition formulas and supplements contain only modest amounts that are likely insufficient to correct vitamin D deficiency or unable to cover even daily requirements of severely ill individuals. In this chapter, the current knowledge on vitamin D is summarized and an overview on data that are specifically relevant to a number of disease states in critically ill patients is given. Readers are also referred to the general aspects of vitamin D as it pertains to acute illness in the chapter by Dr Youssef et al