Supplemental vitamin D and dementia: A sunny outcome? Original paper

In this prospective cohort study, supplementation with vitamin D was associated with longer dementia-free survival and lower risk of incident dementia. However, the benefits of vitamin D varied based on sex, cognitive status, and apolipoprotein E ε4 genotype.

The association between vitamin D exposure and (i) dementia-free survival and (ii) the risk of incident dementia.

12,388 older adults (average age of 71; 56% women, 44% men) recruited from the National Alzheimer's Coordinating Center.

The researchers performed a prospective cohort study with a follow-up period of 10 years. The participants were selected based on vitamin D exposure status (exposure vs. no exposure) at baseline and were without dementia at the start of the study. No information on doses and blood levels of vitamin D were available. The outcomes were adjusted for age, sex, education, ethnicity, depression, cognitive status, and apolipoprotein E ε4 (APOE4, a genetic risk factor associated with an increased risk of dementia) status.

The researchers also assessed whether sex, cognitive status, or APOE4 genotype influenced the outcomes. Moreover, the effect of supplementing with different vitamin D formulations was analyzed, including calcium-vitamin D (a combination supplement used to promote bone health), ergocalciferol or vitamin D2 (derived from plant-based sources), and cholecalciferol or vitamin D3 (found in animal-based sources or synthesized in the skin during sunlight exposure).

Supplemental vitamin D was associated with an increase in 5-year dementia-free survival (+22%) and a decreased risk of incident dementia (−40%).

The association between vitamin D supplementation and dementia varied depending on sex, cognitive status, and APOE4 status. Female participants experienced a greater reduction in the risk of incident dementia compared to male participants (−49% vs. −26%). Participants with normal cognition also showed a larger risk reduction than those with mild cognitive impairment (−56% vs. −33%). Similarly, APOE4 noncarriers had a greater risk reduction compared to APOE4 carriers (−47% vs. −33%).

The benefits of vitamin D supplementation were observed across different formulations. The risk of incident dementia was reduced when supplementing with calcium-vitamin D (−44%), cholecalciferol (−37%), and ergocalciferol (−39%).

This study’s findings suggested that vitamin D supplementation may have the potential to prevent dementia. However, future research is necessary to establish a cause-effect relationship and determine the ideal dosage of vitamin D supplementation for achieving optimal outcomes in dementia prevention.