Cross-sectional associations of plasma vitamin D with cerebral β-amyloid in older adults at risk of dementia oleh Fati Nourhashemi, Claudie Hooper, Christelle Cantet, Catherine Féart, Isabelle Gennero, Pierre Payoux, Anne Sophie Salabert, Sophie Guyonnet, Philipe De Souto Barreto, Bruno Vellas, for the Multidomain Alzheimer Preventive Trial/Data sharing Alzheimer (DSA) study group