Joshua W. Miller, PhD, from Rutgers University in New Brunswick, New Jersey, and colleagues examined the correlation between vitamin D status and trajectories of change in subdomains of cognitive function in a cohort of 382 ethnically diverse older adults (41.4% white, 29.6% African-American, 25.1% Hispanic and 3.9% other race/ethnicity).
Mean 25-hydroxyvitamin D (25[OH]D) level was 19.2 ng/mL; 26.2% and 35.1% of participants were vitamin D deficient and insufficient, respectively, the researchers found. Compared with white participants, the mean 25(OH)D levels were significantly lower for African-American and Hispanic participants (21.7 ng/mL vs. 17.9 ng/mL and 17.2 ng/mL, respectively).
The dementia group had significantly lower mean 25(OH)D compared with the mild cognitive impairment and cognitively normal groups, respectively (16.2 ng/mL vs. 20 ng/mL and 19.7 ng/mL, respectively).
Vitamin D deficient and insufficient participants had greater rates of decline in episodic memory and executive function (vitamin D deficient: P=.49 and P=.01; vitamin D insufficient: P<.001 and P=.008) compared with those with adequate status, after adjustment for confounding variables.
"It remains to be determined whether vitamin D supplementation slows cognitive decline," the researchers wrote.
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