Vitamin D is essential for many organ functions in addition to ensuring strong bones by enhancing calcium absorption. In this latest study, the researchers wanted to see what effect vitamin D status has on the cognitive function of older adults of various ethnic backgrounds. In order to do this, they looked at the baseline levels of vitamin D in a multiethnic group of volunteers and compared those levels with their cognitive function. They also assessed how the change in cognitive function correlated with vitamin D status over time.
There were 382 older adults in the study; their average age was 75 years old. More than half (62%) were women. Although the largest number of participants were white, at 41%, 29.6% were African American and 25% were Hispanic. In terms of cognitive function, at the beginning of the study 49.5% of the participants were cognitively normal, 32.7% were mildly cognitively impaired, and 17.5% had dementia. The investigators measured vitamin D levels with blood (25-OHD).
At baseline, the investigators found that the average 25-OHD levels were lower for the African American (17.9 ng/mL) and Hispanic participants (17.2 ng/mL) when they were compared with the white subjects (21.7 ng/mL). They also noted that average 25-OHD levels were lower in the dementia group than in the mildly cognitive impaired and cognitively normal groups (16.2, 20.0 and 19.7 ng/mL, respectively). On follow-up, which averaged 4.8 years, the researchers found that subjects who had deficient (less than 12 ng/mL) or insufficient (12 to less than 20 ng/mL) vitamin D status had the greatest rates of cognitive decline.
Dr. Miller explained in the audio portion of the news release, “About 60% of the group, regardless of their race or ethnicity, was low in vitamin D. Those low in vitamin D declined more in short term memory, known as episodic memory, as well as more complex cognitive tasks, known as executive function. They were declining about two and a half times faster than those who had adequate vitamin D.”
The researchers call for more studies to determine whether vitamin D supplements can slow cognitive decline.