VDR and Alzheimer disease: Some studies have found older African‐Americans are two to three times more likely to develop AD than elderly caucasians (Alzheimer's, 2014; Amadori et al., 2017) and studies have reported that although African‐American have higher mean VDR levels (Amadori et al., 2017; O'Neill et al., 2013; Richards et al., 2017), they have much lower serum vitamin D concentrations (Dawson‐Hughes, 2004).