Background. Hypovitaminosis D, a common condition in older adults, is ă associated with brain changes and dementia. Given the fast growing ă contribution of literature in this research field, clear guidance is ă needed for clinicians and researchers. Methods. International experts ă met at the invitational summit on ``Vitamin D and cognition in older ă adults'' in Boston, MA, July 2013. Based upon literature and expert ă opinion, the task force focused on key questions on the role of vitamin ă D in Alzheimer disease and related disorders. Each question was ă discussed and voted using a Delphi-like approach. Results. Experts ă reached agreement that hypovitaminosis D increases the risk of cognitive ă decline and dementia in older adults, may alter the clinical ă presentation as a consequence of related comorbidities, but should not ă be used thus far as a diagnostic or prognostic biomarker of Alzheimer ă disease due to lack of specificity and insufficient evidence. ă Hypovitaminosis D should be screened in this population because of its ă high prevalence and supplemented, if necessary, but this advice was not ă specific to cognition. Conclusions. The task force agreed on 5 ă overarching principles related to vitamin D and cognition in older ă adults.