BACKGROUND: Observational studies have consistently found a link between low serum 25-hydroxyvitamin D concentration and higher risk of cognitive impairment. Results from randomized controlled trials have been mixed, and few have been conducted in the general population.
METHODS: We recruited 21,315 community-dwelling Australians aged between 60 and 84 years to participate in the D-Health Trial, a randomized, double-blind, placebo-controlled trial. The intervention was monthly oral doses of 60,000 international units of vitamin D or placebo for 5 years. We assessed cognitive function in a randomly sampled group of participants aged =70 years using the Telephone Interview for Cognitive Status (TICS) at 2 and 5 years after randomization. The primary outcome for this analysis was TICS score; the secondary outcome was the proportion of people who had cognitive impairment (defined as TICS score =25). We analyzed data using mixed models (linear and logistic).
RESULTS: We interviewed 3887 participants at year 2 and 3614 participants at year 5. The mean TICS score at these time points was 32.3 and 32.2, respectively. Vitamin D supplementation did not affect cognitive function as measured by TICS score (mean difference between vitamin D and placebo groups 0.04; 95% CI -0.14 to 0.23), or alter risk of cognitive impairment (odds ratio 1.00; 95% CI 0.75 to 1.33).
CONCLUSIONS: Monthly bolus doses of vitamin D supplementation neither enhanced nor hindered cognitive function among older adults. Population-wide vitamin D supplementation of older adults that are largely vitamin D replete is unlikely to substantially benefit cognition.
This randomized blinded clinical trial with over 21,000 participants demonstrated that 60,000 units monthly of bolus doses of Vitamin D did not improve cognition (measured via telephone at yrs 2 and 5) among a subset of 4019 participants aged 60-84 yrs of age.
Vitamin D has no benefit to the brain.
Carefully conducted study of vitamin D supplementation in seniors with no effect on cognition.
It could be quibbled that the TICS is not the greatest measure of cognition, but other than that, this population-based study appears to confirm that Vit D supplementation is without benefit in those who are not Vit D deficient, at least in regard to cognition. Bad news for the supplement industry, but they are not usually constrained by evidence.
This is not a question that I had nor is it one that has ever been asked by one of my geriatric patients. I think the answer is fairly definitive and that might be worth sharing.
Vitamin D supplementation did not affect cognitive function as measured by TICS score.
Considering the degree to which Vitamin D continues to be "hyped," it is worth knowing that this intervention seems unlikely to be beneficial.