Impact of Vitamin D Supplementation on Cognition in Adults With Mild to Moderate Vitamin D Deficiency: Outcomes From the VitaMIND Randomized Controlled Trial.

OBJECTIVES: Preserved cognitive health with ageing is a public health imperative. Vitamin D deficiency is associated with poor cognition, but it is unclear whether supplementation would provide benefit, particularly in individuals with mild/moderate deficiencies which do not have other clinical risks. The objective of this study was to establish the impact of daily vitamin D supplementation on cognition in older adults with mild to moderate vitamin D deficiency. DESIGN: Two-arm, parallel, 24-month randomized controlled trial, with vitamin D supplementation compared with a placebo. SETTING AND PARTICIPANTS: This was a remote trial, completed from home involving 620 adults, aged ≥ 50 years, with mild to moderate vitamin D deficiency and early cognitive impairment. METHODS: The primary outcome was executive function measured through Trail Making Test Part B and other secondary measures of cognition, function, and well-being. RESULTS: Vitamin D supplementation conferred no significant benefit to executive function compared with placebo at follow-up on the primary outcome (between-group difference, 5770; 95% CI, -2189 to 13,730) or cognition, function, or well-being. Secondary analyses in defined subgroups and a per-protocol analysis also showed no significant impact on any outcome measures. CONCLUSIONS AND IMPLICATIONS: Vitamin D supplementation produced no measurable improvement in cognitive outcomes in older adults with mild to moderate vitamin D deficiency. The remote trial methodology provides an innovative approach to large-scale trials.