Researchers have confirmed a link between vitamin D deficiency and an increased risk of dementia and Alzheimers disease, according to a study published online Aug. 6 in Neurology.
The study focused on 1,658 elderly adults free from dementia, cardiovascular disease and stroke over a period of about six years. The participants in the study had their serum 25-hydroxyvitamin D measured. About 170 subjects developed all-cause dementia during the six-year period and 100 developed Alzheimers disease.
When compared with study participants who had adequate levels of vitamin D (50 nmol/L) or higher, those with deficient levels (25-50 nmol/L) had significantly increased risks for dementia. For participants with severely deficient vitamin D levels, relative risks were even higher for dementia or Alzheimers disease, according to the study.
Our results confirm that vitamin D deficiency is associated with a substantially increased risk of all-cause dementia and Alzheimer disease, the researchers concluded. This adds to the ongoing debate about the role of vitamin D in non-skeletal conditions.
The study also notes that previous research has shown that low vitamin D concentrations in older adults are tied to an increased risk of cognitive decline. This is cause for concern given the high rates of vitamin D deficiency in older adults and continued uncertainty about the causes of [Alzheimers disease] and other forms of dementia, the researchers wrote.
At the same time, preliminary studies have been conflicting, the study found. A study of 40 high-functioning elderly women with severe vitamin D deficiency found that it was associated with non-Alzheimers disease dementias but not Alzheimers disease over seven years. Another study of 10,186 people found severe vitamin D deficiency was associated with medical records showing Alzheimers disease but not vascular dementia over 30 years.
The discrepancy in these findings may be due to a lack of statistical power or use of unstandardized dementia diagnoses from medical records, which may result in considerable misclassification, the researchers wrote. We therefore conducted what is to our knowledge the first large, prospective, population-based study incorporating a comprehensive adjudicated assessment of dementia and [Alzheimers disease] to examine their relationship with vitamin D concentrations.
According to the Alzheimers Association, more than 5 million Americans are living with Alzheimers disease. The disease is the sixth-leading cause of death in the U.S., with one in three seniors dying with Alzheimers or another dementia.
Read the study at http://www.neurology.org/content/early/2014/08/06/WNL.0000000000000755.