Vitamin D Supplementation May Prevent Dementia.
By: Aishah Fadila Adamu.
Relationships between Vitamin D and cognition have been investigated previously with mixed results. While some studies found a connection, some did not.
Dementia is a major neurocognitive disorder characterized by a decline in cognitive abilities notably; learning and memory, language, perception, attention, executive function, and social cognition leading to a reduction in day-to-day functional ability.
Some studies found that low levels of vitamin D in the body is associated with the risk of dementia.
A recent large-scale study was conducted at the University of Calgary’s Hotchkiss Brain Institute in Canada and the University of Exeter in the UK, among 12,388 adults, who had a mean age of 71 and were dementia-free at the time of enrollment. 2,696 participants progressed to dementia over ten years. Amongst them, 2,017 (75%) had had no exposure to Vitamin D prior to dementia diagnosis, and 679 (25%) had baseline exposure. The effects of Vitamin D supplementation were significantly greater in females compared to males and in patients with normal cognitive function compared to those with mild cognitive impairment.
Do these findings mean Vitamin D supplements should be used to prevent dementia?
Professor Zahinoor Ismail, of the University of Calgary and the University of Exeter, who led the research, said: “We know that vitamin D has some effects on the brain that could have implications for reducing dementia, however so far, research has yielded conflicting results. Our findings give key insights into groups that 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.”
Claire Sexton, DPhil, Senior Director of Scientific programs and outreach at the Alzheimer’s Association in Chicago, who wasn’t involved in the study, said the findings don’t mean Vitamin D supplements should be used to prevent dementia. She added that the study is not an intervention, so it cannot establish causation.
The researchers also acknowledged several limitations of the study. These include the fact that the NACC (National Association of Career Colleges) sheet from which the participants were enrolled had no record information about exposure history, and there was no accounting for differences in exposure duration, baseline levels and different dosing. Whether the incident dementia rates differed based on dosing or Vitamin D deficiency is unknown.
There were other confounding factors. For instance, the exposed group had higher educational levels, and both mild cognitive impairment and depression were frequent in the non-exposed group. Higher education is a known protective factor while depression is a risk factor for dementia.