Cross-sectional associations of plasma vitamin D with cerebral β-amyloid in older adults at risk of dementia

Background: Vitamin D deficiency is associated with an increased risk of Alzheimer's disease and increased beta-amyloid (A beta) in animals. Hence we sought to investigate the relationship between plasma 25-hydroxyvitamin D (25(OH) D) and cerebral A beta in older adults with subjective memory complaints. Methods: This is a secondary analysis of the Multidomain Alzheimer Preventive Trial. Participants were 178 dementiafree individuals aged 70 years or older with data on plasma 25(OH) D and cerebral A beta load assessed by [F-18]-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 A beta in any of the brain regions studied. Conclusions: These preliminary results suggest that circulating 25(OH) D is not associated with cerebral A beta 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 A beta accrual over time, thereby circumventing the shortfalls of a cross-sectional study.