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To the Editor We read with interest the article by Miller et al.1 In a general population, it was demonstrated for the first time that vitamin D insufficiency, which was more frequently observed in African American and Hispanic individuals, was associated with significantly faster declines in both episodic memory and executive function performance. We agree with the authors that a lower vitamin D status may be associated with an increased risk for developing Alzheimer disease and dementia, as confirmed by a recent meta-analysis.2 However, measurement of the bioavailable 25-hydroxyvitamin D fraction may be a more reliable cross-racial marker of the vitamin D status compared with the total 25-hydroxyvitamin D levels.3 Because African American and Hispanic individuals have frequently lower total 25-hydroxyvitamin D levels, they are consistently classified as being vitamin D deficient.4
Speeckaert MM, Delanghe JR. 25-Hydroxyvitamin D in Patients With Cognitive Decline. JAMA Neurol. 2016;73(3):356-357. doi:10.1001/jamaneurol.2015.4182