An observational study examining over 12,000 older adults found that those who took vitamin D supplements were less likely to develop cognitive impairments.
Recent reports indicate that high vitamin D levels in the brain may be linked to better cognitive function. Moreover, previous research also found associations between low vitamin D levels and an increased risk of cognitive decline.
However, few studies have examined whether taking vitamin D supplements impacts dementia risk.
In a new study published on March 1 in Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring, scientists from the University of Exeter in the United Kingdom and the University of Calgary’s Hotchkiss Brain Institute in Canada found that vitamin D supplementation may be associated with a reduced risk of dementia.
Specifically, they found that people who took vitamin D supplements had fewer dementia diagnoses than those who did not.
The prospective cohort study examined 12,388 participants from the U.S. National Alzheimer's Coordinating Center dataset. The participant’s average age was 71 years, and none had dementia at the study’s onset.
The research team noted which participants had exposure to vitamin D and which did not. Then, they assessed the participant’s dementia incidence rates and adjusted for age, sex, race, education, cognitive diagnosis, depression, and apolipoprotein E (APOE) ε4 — a gene linked to the development of Alzheimer’s disease.
Over 10 years, 2,696 participants developed dementia. Among them, 679 had taken vitamin D, and 2,017 had no history of vitamin D supplementation.
The scientists also found that exposure to vitamin D was associated with a significantly lower rate of dementia in people who carried the APOE gene and those who did not. However, the effects were more pronounced in people who were not APOE carriers.
In addition, these findings were consistent across three supplement types — calcium/vitamin D combinations, cholecalciferol (Vitamin D3), and ergocalciferol (vitamin D2).
Overall, the scientists say that vitamin D supplementation was associated with a 40% lower incidence of dementia.
"Our findings give key insights into groups who might be specifically targeted for vitamin D supplementation. Overall, we found evidence to suggest that earlier supplementation might be particularly beneficial, before the onset of cognitive decline," says lead researcher Professor Zahinoor Ismail, of the University of Calgary and the University of Exeter, in a news release.
Still, the study had some limitations. For example, the scientists did not have information on the dosages of vitamin D, so it is unclear if the lower incidences of dementia were dose-dependent. In addition, the study did not assess other supplements that could contribute to lowered dementia risk. Lastly, sun exposure — which can naturally increase vitamin D in the body — was not considered.
The scientists suggest that future studies consider differences in sex, race, sun exposure, and APOE status when recruiting participants. Moreover, examining how different vitamin D doses impact dementia risk could offer insight into how much vitamin D an individual needs for optimal brain health.
- Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring. Vitamin D supplementation and incident dementia: Effects of sex, APOE, and baseline cognitive status.
- EurekAlert. Taking vitamin D could help prevent dementia, study finds.