The 382 research participants were an average age of 75.5 years. Nearly 62 percent were female, while 41.4 percent were white, 29.6 percent were African American and 25.1 percent were Hispanic. At study enrollment, 17.5 percent of the participants had dementia, 32.7 percent had mild cognitive impairment and 49.5 percent were cognitively normal.
Vitamin D deficiency was measured by taking blood samples and vitamin D status was defined as follows: deficient was less than 12 ng/mL; insufficient was 12 to less than 20 ng/mL; adequate was 20 to less than 50 ng/mL; and high was 50 ng/mL or higher.
The results indicate the following:
The average 25-OHD level among participants was 19.2 ng/mL, with 26.2 percent of participants being vitamin D deficient and 35.1 percent vitamin D insufficient.
Average 25-OHD levels were lower for African American and Hispanic participants compared with their white counterparts (17.9, 17.2 and 21.7 ng/mL, respectively).
Average 25-OHD levels were lower in the dementia group compared with mild cognitive impairment and cognitively normal groups (16.2, 20.0 and 19.7 ng/mL, respectively.
During an average follow-up of 4.8 years, rates of decline in episodic memory and executive function among vitamin D deficient and vitamin D insufficient participants were greater than those with adequate vitamin D status after adjusting for a variety of patient factors.
“Our data support the common occurrence of VitD [vitamin D] insufficiency among older individuals”, said Dr. Joshua W. Miller.”In addition, these data show that African American and Hispanic individuals are more likely to have VitD insufficiency or deficiency. Independent of race or ethnicity, baseline cognitive ability, and a host of other risk factors, VitD insufficiency was associated with significantly faster declines in both episodic memory and executive function performance, which may correspond to elevated risk for incident AD [Alzheimer disease] dementia. Given that VitD insufficiency is medically correctable, well-designed clinical trials that emphasize enrollment of individuals of nonwhite race/ethnicity with hypovitaminosis D could be useful for testing the effect of VitD replacement on dementia prevention.”
“Independent of race or ethnicity, baseline cognitive abilities and a host of other risk factors, vitamin D insufficiency was associated with significantly faster declines in both episodic memory and executive function performance,” said Joshua Miller.
“This work, and that of others, suggests that there is enough evidence to recommend that people in their 60s and older discuss taking a daily vitamin D supplement with their physicians,” Miller said
Vitamin D impacts on all organ systems. The vitamin D receptor and the enzyme that converts 25-hydroxyvitamin D (25-OHD) to the active form of the vitamin are expressed in all human organs, including the brain.
Low vitamin D levels associated with more rapid cognitive decline in older adults, Joshua W. Miller et al., JAMA Neurology, doi:10.1001/jamaneurol.2015.2115, published online 14 September 2015.