Higher levels of vitamin D in the blood during middle age are associated with lower amounts of tau protein in the brain, a marker linked to dementia, according to a study published on April 1 in Neurology Open Access. The research does not establish that vitamin D reduces tau or prevents dementia, but shows an association between these factors.
The findings may be important for understanding how modifiable risk factors could influence the development of dementia. Researchers say further studies are needed to confirm whether improving vitamin D status can help reduce risk.
"These results suggests that higher vitamin D levels in midlife may offer protection against developing these tau deposits in the brain and that low vitamin D levels could potentially be a risk factor that could be modified and treated to reduce the risk of dementia," said Martin David Mulligan, MB BCh BAO, of the University of Galway in Ireland. "Of course, these results need to be further tested with additional studies."
The study followed 793 participants who were on average 39 years old and did not have dementia at enrollment. Vitamin D blood levels were measured at the start; brain scans measuring tau and amyloid beta proteins—both considered Alzheimer's disease biomarkers—were performed about 16 years later. A high level of vitamin D was defined as greater than 30 nanograms per milliliter (ng/mL), while low was below this threshold.
Researchers found that people with higher midlife vitamin D had lower tau protein years later. There was no link between vitamin D and amyloid beta protein amounts. Thirty-four percent had low vitamin D at baseline; only five percent used supplements.
Mulligan said: "These results are promising, as they suggest an association between higher Vitamin D levels in early middle-age and lower tau burden on average 16 years later. Mid-life is a time where risk factor modification can have a greater impact." The authors noted one limitation: participants' blood was tested for vitamin D only once during the study period.
The work received support from several organizations including the National Institute on Aging, National Institute of Neurological Disorders and Stroke, Irish Research Council, and Health Research Board of Ireland.
