About 42 percent of the general U.S. population has low vitamin D levels. In addition to promoting calcium and bone health, vitamin D may also affect the brain and cognitive function. A new study by JAMA Neurology looked at the association between baseline vitamin D levels and the rate of cognitive decline in a group of ethnically diverse older adults.
A researcher from Rutgers University, along with colleagues from the University of California Davis, studied 382 older adults with an average age of 75. Among the group, 61 percent of participants were women, 41 percent white, about 30 percent were African American and 25 percent were Hispanic. At study enrollment, about 18 percent had dementia, 33 percent had mild cognitive impairment and half were cognitively normal.
Vitamin D levels and cognitive function were measured at baseline. Cognitive function was also followed in 318 of the participants for an average of 5 years.
- About 60 percent of the group, regardless of their race or ethnicity, was low in vitamin D.
- Vitamin D levels were lower for African American and Hispanics, compared with their white counterparts.
- Participants in the dementia group had lower vitamin D levels compared with the mild cognitive impairment and cognitively normal groups.
- 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.
- Vitamin D status was not significantly associated with decline in semantic memory or visuospatial ability.
The authors note limitations to their study including the inability to directly measure dairy intake, sun exposure or exercise, each of which can influence vitamin D levels.