Older March 9, 2023  adults who take vitamin D may be 40% less likely to develop dementia compared with those who do not, according to a study published in Alzheimer’s & Dementia.“Vitamin D deficiency may be a modifiable risk factor [for dementia] and has been recognized as a widespread health problem, with a worldwide prevalence of up to 1 billion,” wrote Zahinoor Ismail, M.D., of the University of Calgary and colleagues. “Yet, the role of vitamin D supplementation as a potential intervention has been a subject of debate and remains in equipoise.” Ismail and colleagues used 2005-2021 data from the National Alzheimer’s Coordinating Center (NACC), which includes data on cognitive functioning from participants in the Alzheimer’s Disease Research Center. NACC collects demographic and standardized clinical data annually. Participants who had either normal cognition or mild cognitive impairment at baseline were included in the study. They were then divided into two groups: the vitamin D–exposed group, those who were taking either calcium-vitamin D, cholecalciferol (vitamin D3), or ergocalciferol (vitamin D2) at baseline; and the non-exposed group, those who were not taking vitamin D supplements during the study period (or prior to a dementia diagnosis).A total of 12,388 participants were included, with 4,637 in the vitamin D–exposed group and 7,751 in the non-exposed group. After five years, 83.6% of those exposed to vitamin D had not developed dementia, compared with 68.4% of those not exposed to vitamin D. After controlling for baseline age, sex, education, race, cognitive diagnosis, depression, and APOE ε4 status (a gene associated with an increased risk of Alzheimer’s), almost 75% of those who developed dementia over 10 years had no exposure to vitamin D prior to their diagnoses. These findings were consistent across all vitamin D formulations included in the study. Additional findings included the following:

• Women taking vitamin D had lower rates of dementia compared with men taking vitamin D.
• Though mild cognitive impairment at baseline was associated with more dementia diagnoses after five years compared with normal cognition at baseline, exposure to vitamin D was associated with lower odds of developing dementia after five years among both those with mild cognitive impairment and normal cognition at baseline.
• Though a depression diagnosis was associated with a 35% greater incidence of dementia, the study did not identify any significant interaction between depression and vitamin D exposure.

“[O]ur findings implicate vitamin D as a potential agent for dementia prevention and provide additional support for its use in at-risk individuals,” the authors wrote. “Information on dosage of vitamin D supplementation as well as the baseline levels of vitamin D will be essential to further clarify the efficacy and refine the target population for vitamin D supplementation in preventing [Alzheimer’s] and dementia.” (SOURCE: APA Psychiatric New Alert)