Low levels of vitamin D are associated with more rapid cognitive decline among older people, according to a new study titled “Vitamin D Status and Rates of Cognitive Decline in a Multiethnic Cohort of Older Adults” appearing online in the medical journal JAMA Neurology. The authors are Joshua W. Miller, PhD, of the Department of Nutritional Sciences at Rutgers University, New Brunswick, NJ, and his colleagues from the University of California, Davis.

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.