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Randomized Controlled Trial
. 2025 Jun 10;80(7):glaf077.
doi: 10.1093/gerona/glaf077.

The Effect of Vitamin D3 Supplementation on the Incidence of Diagnosed Dementia Among Healthy Older Adults-The Finnish Vitamin D Trial

Eija Lönnroos  1 , Maija Ylilauri  1 , Christel Lamberg-Allardt  2 , JoAnn E Manson  3   4 , Tarja Nurmi  1 , Matti Uusitupa  1 , Ari Voutilainen  1 , Sari Hantunen  1 , Tomi-Pekka Tuomainen  1 , Jyrki K Virtanen  1
Affiliations
Randomized Controlled Trial

The Effect of Vitamin D3 Supplementation on the Incidence of Diagnosed Dementia Among Healthy Older Adults-The Finnish Vitamin D Trial

Eija Lönnroos et al. J Gerontol A Biol Sci Med Sci. .

Abstract

Background: Some short-term vitamin D supplementation trials suggest benefits on cognitive performance, but apart from observational studies, there is little evidence whether long-term vitamin D supplementation can prevent development of dementia. We investigated whether vitamin D3 supplementation could affect the incidence of diagnosed dementia in a generally healthy population.

Methods: The study included 2 492 participants from the Finnish Vitamin D Trial, free of diagnosed dementia at baseline. They were randomized to placebo, 1 600 IU/d, or 3 200 IU/d of vitamin D3 arm for up to 5 years. Incident diagnoses of dementia were obtained from the national care registries.

Results: The mean age of the participants at baseline was 68.2 years and 42.8% were female. During the mean follow-up of 4.2 years, 18 participants in the placebo arm, 14 participants in the 1 600 IU/d arm (compared to placebo, hazard ratio [HR] = 0.77, 95% confidence interval [CI]: 0.38-1.55), and 13 participants in the 3 200 IU/d arm (HR = 0.72, 95% CI: 0.35-1.48) were diagnosed with dementia. Of the diagnoses, 29 were Alzheimer's disease, without statistically significant differences in the event rates between the 3 arms. Age, sex, or body mass index did not modify the effects. In the subgroup of 550 participants, the mean baseline serum 25-hydroxyvitamin D concentration was 74.8 nmol/L. After 12 months, the mean concentrations were 73.0, 99.7, and 120.4 nmol/L in the placebo, 1 600 IU/d, and 3 200 IU/d arms, respectively.

Conclusions: Five-year, medium-dose or high-dose vitamin D3 supplementation did not affect the dementia incidence in this largely vitamin D-sufficient older population.

Clinical trial registry number: ClinicalTrials.gov: NCT01463813, https://clinicaltrials.gov/ct2/show/NCT01463813.

Keywords: Cognitive decline; General population; Randomized controlled trial.

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Conflict of interest statement

J.K.V. reports receiving travel support to vitamin D research meetings from Abiogen Pharma. C.L.-A. reports involvement in the Nordic Nutrition recommendations 2023 as a member of the Systematic Review Centre, and in European Food Safety Authority, procurement, preparatory work for the update of the tolerable upper intake levels for vitamin D, 2023. J.E.M. reports receiving grants from the National Institutes of Health during the conduct of the study, and grants from the National Institutes of Health and from Mars Edge outside the submitted work. M.U. reports receiving a grant from Orion Corp., outside the submitted work. The other authors declare no conflict.

Figures

Figure 1.
Figure 1.
Participant flow chart.
Figure 2.
Figure 2.
Cumulative incidence of dementia in the 3 study arms during the 5-y supplementation period and in the extended post-supplementation follow-up.
See this image and copyright information in PMC

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