Effects of vitamin D supplementation on cognitive function and blood Aβ-related biomarkers in older adults with Alzheimer's disease: a randomised, double-blind, placebo-controlled trial

Objective Our study aimed to assess the effect of a 12-month vitamin D supplementation on cognitive function and amyloid beta (A beta)-related biomarkers in subjects with Alzheimer's disease (AD). Methods This was a randomised, double-blind, placebo-controlled trial. 210 AD patients were randomly divided into intervention and control groups. Participants received 12-month 800 IU/day of vitamin D or starch granules as placebo. Tests of cognitive performance and A beta-related biomarkers were measured at baseline, 6 months and 12 months. Results Repeated-measures analysis of variance showed significant improvements in plasma A beta 42, APP, BACE 1, APPmRNA, BACE 1 mRNA (p<0.001) levels and information, arithmetic, digit span, vocabulary, block design and picture arrange scores (p<0.05) in the intervention group over the control group. According to mixed-model analysis, vitamin D group had significant increase in full scale IQ during follow-up period (p<0.001). Conclusions Daily oral vitamin D supplementation (800 IU/day) for 12 months may improve cognitive function and decrease A beta-related biomarkers in elderly patients with AD. Larger scale longer term randomised trials of vitamin D are needed.